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Stabile M, Esposito A, Iula VD, Guaragna A, De Gregorio E. PYED-1 Overcomes Colistin Resistance in Acinetobacter baumannii. Pathogens 2023; 12:1323. [PMID: 38003788 PMCID: PMC10674209 DOI: 10.3390/pathogens12111323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 10/21/2023] [Accepted: 10/31/2023] [Indexed: 11/26/2023] Open
Abstract
Antibiotic resistance has become more and more widespread over the recent decades, becoming a major global health problem and causing colistin to be increasingly used as an antibiotic of last resort. Acinetobacter baumannii, an opportunistic pathogen that has rapidly evolved into a superbug exhibiting multidrug-resistant phenotypes, is responsible for a large number of hospital infection outbreaks. With the intensive use of colistin, A. baumannii resistance to colistin has been found to increase significantly. In previous work, we identified a deflazacort derivative, PYED-1 (pregnadiene-11-hydroxy-16,17-epoxy-3,20-dione-1), which exhibits either direct-acting or synergistic activity against Gram-positive and Gram-negative species and Candida spp., including A. baumannii. The aim of this study was to evaluate the antibacterial activity of PYED-1 in combination with colistin against both A. baumannii planktonic and sessile cells. Furthermore, the cytotoxicity of PYED-1 with and without colistin was assessed. Our results show that PYED-1 and colistin can act synergistically to produce a strong antimicrobial effect against multidrug-resistant populations of A. baumannii. Interestingly, our data reveal that PYED-1 is able to restore the efficacy of colistin against all colistin-resistant A. baumannii isolates. This drug combination could achieve a much stronger antimicrobial effect than colistin while using a much smaller dosage of the drugs, additionally eliminating the toxicity and resistance issues associated with the use of colistin.
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Affiliation(s)
- Maria Stabile
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126 Naples, Italy; (M.S.); (A.G.)
- Department of Molecular Medicine and Medical Biotechnologies, University of Naples Federico II, Via S. Pansini 5, 80131 Naples, Italy
| | - Anna Esposito
- Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale V. Tecchio 80, 80125 Naples, Italy;
| | - Vita Dora Iula
- Department of Laboratory Medicine, U.O.C Patologia Clinica, Ospedale del Mare—ASL Napoli1 Centro, 80145 Naples, Italy;
| | - Annalisa Guaragna
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126 Naples, Italy; (M.S.); (A.G.)
| | - Eliana De Gregorio
- Department of Molecular Medicine and Medical Biotechnologies, University of Naples Federico II, Via S. Pansini 5, 80131 Naples, Italy
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Colistin Resistance in Acinetobacter baumannii: Molecular Mechanisms and Epidemiology. Antibiotics (Basel) 2023; 12:antibiotics12030516. [PMID: 36978383 PMCID: PMC10044110 DOI: 10.3390/antibiotics12030516] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/17/2023] [Accepted: 03/02/2023] [Indexed: 03/08/2023] Open
Abstract
Acinetobacter baumannii is recognized as a clinically significant pathogen causing a wide spectrum of nosocomial infections. Colistin was considered a last-resort antibiotic for the treatment of infections caused by multidrug-resistant A. baumannii. Since the reintroduction of colistin, a number of mechanisms of colistin resistance in A. baumannii have been reported, including complete loss of LPS by inactivation of the biosynthetic pathway, modifications of target LPS driven by the addition of phosphoethanolamine (PEtN) moieties to lipid A mediated by the chromosomal pmrCAB operon and eptA gene-encoded enzymes or plasmid-encoded mcr genes and efflux of colistin from the cell. In addition to resistance to colistin, widespread heteroresistance is another feature of A. baumannii that leads to colistin treatment failure. This review aims to present a critical assessment of relevant published (>50 experimental papers) up-to-date knowledge on the molecular mechanisms of colistin resistance in A. baumannii with a detailed review of implicated mutations and the global distribution of colistin-resistant strains.
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Choudhary M, Shrivastava R, Vashistt J. Acinetobacter baumannii Biofilm Formation: Association with Antimicrobial Resistance and Prolonged Survival under Desiccation. Curr Microbiol 2022; 79:361. [PMID: 36253556 DOI: 10.1007/s00284-022-03071-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/29/2022] [Indexed: 11/30/2022]
Abstract
Biofilm-forming multidrug-resistant Acinetobacter baumannii has emerged as a global pathogen. This study investigated the impact of biofilm formation by A. baumannii on antimicrobial resistance and prolonged survival under desiccation, which is essential for effective infection control of A. baumannii in hospital settings. Seventy-eight clinical isolates of A. baumannii were identified, and antibiotic susceptibility profiles were assessed. All the isolates were investigated for their biofilm-forming abilities at 24 and 48 h. The biofilm inhibitory concentrations of antibiotics were evaluated for selected biofilm-forming isolates to determine the influence of biofilm on antibiotic tolerance. The impact of biofilm formation on desiccation tolerance was also evaluated for up to 48 days. The results revealed that out of 78 A. baumannii clinical isolates, 83% were MDR and 17% non-MDR. Overall, 79% of isolates formed high biofilm after 24 h. The extent of biofilm formation gets significantly increased after 48 h, and 87% of isolates formed high biofilm. It was observed that eradicating mature biofilm requires up to a thousandfold higher concentration of antibiotics than MICs, and biofilm-forming isolates can survive for a prolonged period under desiccation. In conclusion, our findings revealed that both MDR and non-MDR isolates of A. baumannii could form biofilms on abiotic surfaces. A. baumannii biofilms contribute to endurance in the presence of antimicrobials and desiccation conditions, which are significant trouble for hospital patient care management. The present findings may offer insights for developing preventive measures to tackle biofilm-associated A. baumannii infection.
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Affiliation(s)
- Monika Choudhary
- Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh, 173234, India
| | - Rahul Shrivastava
- Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh, 173234, India
| | - Jitendraa Vashistt
- Department of Biotechnology & Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh, 173234, India.
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Constitutive Phenotypic Modification of Lipid A in Clinical Acinetobacter baumannii Isolates. Microbiol Spectr 2022; 10:e0129522. [PMID: 35861511 PMCID: PMC9431647 DOI: 10.1128/spectrum.01295-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The degree of polymyxin B (PMB) resistance was measured in 40 clinical Acinetobacter baumannii isolates obtained from health care facilities. All of the tested isolates possessed a multidrug-resistant (MDR) phenotype against four classes of antibiotics (meropenem, doxycycline, gentamicin, and erythromycin), except for PMB. The blaOXA-23 gene was detected throughout the genetic analysis and experimental assay, indicating that all of the MDR strains were carbapenem-resistant A. baumannii strains. Multilocus sequence typing-based genotyping revealed that nine selected strains belonged to the international clone II lineage. When matrix-assisted laser desorption ionization–time of flight mass spectrometry was performed, intrinsic lipid A modification by phosphoethanolamine (PEtN) incorporation was noticeable only in the PMB-resistant (PMBR) strains. However, the presence of hexa- and penta-acylated lipid A due to the loss of the laurate (C12) acyl chain was noted in all PMB-susceptible strains but not in the PMBR strains. The reduction of negative surface charges in the PMBR strains was assessed by zeta potential analysis. Fluorescence imaging using dansyl-PMB revealed that, in the PMBR strains, PMB was less likely to bind to the cell surface. IMPORTANCE The widespread presence of MDR pathogens, including A. baumannii, is causing serious hospital-acquired infections worldwide. Extensive surveillance of MDR clinical A. baumannii isolates has been conducted, but the underlying mechanisms for their development of MDR phenotypes are often neglected. Either lipid A modification or loss of lipopolysaccharide in Gram-negative bacteria leads to PMBR phenotypes. The prevalence of intrinsic lipid A modification in PMBR clinical strains was attributed to high levels of basal expression of pmrC and eptA-1. Our findings suggest that new therapeutic strategies are warranted to combat MDR pathogens due to the emergence of many PMBR clinical strains.
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Kim SE, Choi SM, Yu Y, Shin SU, Oh TH, Kang SJ, Park KH, Shin JH, Kim UJ, Jung SI. Replacement of the Dominant ST191 Clone by ST369 Among Carbapenem-Resistant Acinetobacter baumannii Bloodstream Isolates at a Tertiary Care Hospital in South Korea. Front Microbiol 2022; 13:949060. [PMID: 35910596 PMCID: PMC9335038 DOI: 10.3389/fmicb.2022.949060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 06/21/2022] [Indexed: 11/13/2022] Open
Abstract
The clonal dissemination of carbapenem-resistant Acinetobacter baumannii (CRAB) bacteremia is a serious clinical problem worldwide. However, the factors related to the emergence and replacement of predominant CRAB clones in nosocomial settings are unclear. By multilocus sequence typing (MLST), we evaluated the genetic relatedness of CRAB bloodstream isolates at a tertiary care hospital over a 3.5-year period and investigated the clinical and microbiologic characteristics of the predominant sequence types (STs). One hundred and seventy-nine CRAB bloodstream isolates were collected from June 2016 to December 2019, and their MLSTs according to Oxford scheme and clinical data were obtained. The predominant STs were assessed for in vitro growth, competitive growth, and virulence in a mouse model of intraperitoneal infection. Two dominant clones—ST369 (n = 98) and ST191 (n = 48)—belonging to international clone 2 (IC2) were recovered from patients admitted to intensive care units (ICUs) or wards. ST191 predominated (61%, 27/43) from June 2016 to July 2017, whereas ST369 (72%, 98/136), which was first isolated from a patient admitted to the emergency room, replaced ST191 (15%, 21/136) after August 2017. In a multivariate analysis, leukopenia (OR = 3.62, 95% CI 1.04–12.6, p = 0.04) and ST191 or 369 (OR = 5.32, 95% CI 1.25–22.65, p = 0.02) were independent risk factors for 7-day mortality. Compared with non-ST369, ST369 was associated with a shorter time to bacteremia from ICU admission (7 vs. 11 days, p = 0.01), pneumonia as an origin of bacteremia (67 vs. 52%, p = 0.04), leukopenia (28 vs. 11%, p < 0.01), and a lower 7-day survival rate (41 vs. 70%, p < 0.01). In vitro, ST 369 isolates had significantly higher growth rates and enhanced competitive growth compared to ST191. Finally, ST369 had greater virulence and a higher mortality rate than other STs in a mouse infection model. We report almost-complete replacement of the predominant ST191 clone by ST369 within an 8-month period at our hospital. ST369 had a high incidence density rate of CRAB bacteremia, a short time to bacteremia after ICU admission, and a high early mortality rate, which may be in part explained by its faster competitive growth rate and higher virulence than ST191.
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Affiliation(s)
- Seong Eun Kim
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Su-Mi Choi
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Yohan Yu
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Sung Un Shin
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Tae Hoon Oh
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Seung-Ji Kang
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Kyung-Hwa Park
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
| | - Jong Hee Shin
- Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, South Korea
| | - Uh Jin Kim
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
- Uh Jin Kim,
| | - Sook In Jung
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, South Korea
- *Correspondence: Sook In Jung,
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Fortuin S, Soares NC. The Integration of Proteomics and Metabolomics Data Paving the Way for a Better Understanding of the Mechanisms Underlying Microbial Acquired Drug Resistance. Front Med (Lausanne) 2022; 9:849838. [PMID: 35602483 PMCID: PMC9120609 DOI: 10.3389/fmed.2022.849838] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 04/14/2022] [Indexed: 11/13/2022] Open
Abstract
Due to an increase in the overuse of antimicrobials and accelerated incidence of drug resistant pathogens, antimicrobial resistance has become a global health threat. In particular, bacterial antimicrobial resistance, in both hospital and community acquired transmission, have been found to be the leading cause of death due to infectious diseases. Understanding the mechanisms of bacterial drug resistance is of clinical significance irrespective of hospital or community acquired since it plays an important role in the treatment strategy and controlling infectious diseases. Here we highlight the advances in mass spectrometry-based proteomics impact in bacterial proteomics and metabolomics analysis- focus on bacterial drug resistance. Advances in omics technologies over the last few decades now allows multi-omics studies in order to obtain a comprehensive understanding of the biochemical alterations of pathogenic bacteria in the context of antibiotic exposure, identify novel biomarkers to develop new drug targets, develop time-effectively screen for drug susceptibility or resistance using proteomics and metabolomics.
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Affiliation(s)
- Suereta Fortuin
- African Microbiome Institute, General Internal Medicine, Stellenbosch University, Cape Town, South Africa
- *Correspondence: Suereta Fortuin
| | - Nelson C. Soares
- College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
- Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates
- Nelson C. Soares
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Acinetobacter Baumannii: More Ways to Die. Microbiol Res 2022; 261:127069. [DOI: 10.1016/j.micres.2022.127069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/06/2022] [Accepted: 05/09/2022] [Indexed: 11/17/2022]
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Xie M, Chen K, Dong N, Xu Q, Chan EWC, Zhang R, Chen S. Phenotypic Changes Associated With In Vivo Evolution of Colistin Resistance in ST11 Carbapenem-Resistant Klebsiella pneumoniae. Front Cell Infect Microbiol 2022; 12:841748. [PMID: 35281457 PMCID: PMC8907821 DOI: 10.3389/fcimb.2022.841748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 02/08/2022] [Indexed: 11/26/2022] Open
Abstract
Colistin is one of the few antibiotics that exhibit bactericidal effect on carbapenemase-producing Klebsiella pneumoniae strains. In recent years, however, colistin resistance is increasingly being reported among clinical carbapenem-resistant K. pneumoniae strains worldwide, posing serious challenge to treatment of infections caused by these organisms. In this study, we investigated one colistin-susceptible (YJH4) and one colistin-resistant (YJH15) K. pneumoniae strain, which were collected from a patient before and after colistin treatment, respectively. We characterized the effects of mgrB inactivation-induced colistin resistance on the physiological fitness and virulence in ST11 carbapenem-resistant K. pneumoniae both in vitro and in vivo. The colistin-resistant strain YJH15 was found to exhibit increased fitness and biofilm formation potential in vitro, and increased survival rate in the presence of normal human serum. Interestingly, YJH15 exhibited reduced virulence in the mouse infection model but enhanced virulence in Galleria mellonella infection model when compared to the colistin-susceptible parental strain YJH4. Infection with YJH15 was also found to result in lower expression level of inflammatory cytokine IL-1β in blood and significantly decreased bacterial loads in heart, liver, spleen, lung, kidney and blood. These results demonstrated that mgrB inactivation-induced colistin resistance has significant effects on multiple fitness and virulence-associated traits in K. pneumoniae.
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Affiliation(s)
- Miaomiao Xie
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Kaichao Chen
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Ning Dong
- Department of Medical Microbiology, School of Biology and Basic Medical Science, Medical College of Soochow University, Suzhou, China
| | - Qi Xu
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Edward Wai-Chi Chan
- State Key Lab of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, Hong Kong SAR, China
| | - Rong Zhang
- Department of Clinical Laboratory, School of Medicine, Second Affiliated Hospital of Zhejiang University, Hangzhou, China
| | - Sheng Chen
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Hong Kong, Hong Kong SAR, China
- *Correspondence: Sheng Chen,
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Cianciulli Sesso A, Lilić B, Amman F, Wolfinger MT, Sonnleitner E, Bläsi U. Gene Expression Profiling of Pseudomonas aeruginosa Upon Exposure to Colistin and Tobramycin. Front Microbiol 2021; 12:626715. [PMID: 33995291 PMCID: PMC8120321 DOI: 10.3389/fmicb.2021.626715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/31/2021] [Indexed: 11/22/2022] Open
Abstract
Pseudomonas aeruginosa (Pae) is notorious for its high-level resistance toward clinically used antibiotics. In fact, Pae has rendered most antimicrobials ineffective, leaving polymyxins and aminoglycosides as last resort antibiotics. Although several resistance mechanisms of Pae are known toward these drugs, a profounder knowledge of hitherto unidentified factors and pathways appears crucial to develop novel strategies to increase their efficacy. Here, we have performed for the first time transcriptome analyses and ribosome profiling in parallel with strain PA14 grown in synthetic cystic fibrosis medium upon exposure to polymyxin E (colistin) and tobramycin. This approach did not only confirm known mechanisms involved in colistin and tobramycin susceptibility but revealed also as yet unknown functions/pathways. Colistin treatment resulted primarily in an anti-oxidative stress response and in the de-regulation of the MexT and AlgU regulons, whereas exposure to tobramycin led predominantly to a rewiring of the expression of multiple amino acid catabolic genes, lower tricarboxylic acid (TCA) cycle genes, type II and VI secretion system genes and genes involved in bacterial motility and attachment, which could potentially lead to a decrease in drug uptake. Moreover, we report that the adverse effects of tobramycin on translation are countered with enhanced expression of genes involved in stalled ribosome rescue, tRNA methylation and type II toxin-antitoxin (TA) systems.
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Affiliation(s)
- Anastasia Cianciulli Sesso
- Max Perutz Labs, Vienna Biocenter (VBC), Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
| | - Branislav Lilić
- Max Perutz Labs, Vienna Biocenter (VBC), Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
| | - Fabian Amman
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria
| | - Michael T Wolfinger
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria.,Research Group Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, Vienna, Austria
| | - Elisabeth Sonnleitner
- Max Perutz Labs, Vienna Biocenter (VBC), Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
| | - Udo Bläsi
- Max Perutz Labs, Vienna Biocenter (VBC), Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna, Austria
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Martínez-Guitián M, Vázquez-Ucha JC, Álvarez-Fraga L, Conde-Pérez K, Bou G, Poza M, Beceiro A. Antisense inhibition of lpxB gene expression in Acinetobacter baumannii by peptide-PNA conjugates and synergy with colistin. J Antimicrob Chemother 2021; 75:51-59. [PMID: 31586411 DOI: 10.1093/jac/dkz409] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 08/28/2019] [Accepted: 09/03/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND LpxB is an enzyme involved in the biosynthesis pathway of lipid A, a component of LPS. OBJECTIVES To evaluate the lpxB gene in Acinetobacter baumannii as a potential therapeutic target and to propose antisense agents such as peptide nucleic acids (PNAs) as a tool to combat bacterial infection, either alone or in combination with known antimicrobial therapies. METHODS RNA-seq analysis of the A. baumannii ATCC 17978 strain in a murine pneumonia model was performed to study the in vivo expression of lpxB. Protein expression was studied in the presence or absence of anti-lpxB (KFF)3K-PNA (pPNA). Time-kill curve analyses and protection assays of infected A549 cells were performed. The chequerboard technique was used to test for synergy between pPNA and colistin. A Galleria mellonella infection model was used to test the in vivo efficacy of pPNA. RESULTS The lpxB gene was overexpressed during pneumonia. Treatment with a specific pPNA inhibited LpxB expression in vitro, decreased survival of the ATCC 17978 strain and increased the survival rate of infected A549 cells. Synergy was observed between pPNA and colistin in colistin-susceptible strains. In vivo assays confirmed that a combination treatment of anti-lpxB pPNA and colistin was more effective than colistin in monotherapy. CONCLUSIONS The lpxB gene is essential for A. baumannii survival. Anti-lpxB pPNA inhibits LpxB expression, causing bacterial death. This pPNA showed synergy with colistin and increased the survival rate in G. mellonella. The data suggest that antisense pPNA molecules blocking the lpxB gene could be used as antibacterial agents.
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Affiliation(s)
- Marta Martínez-Guitián
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Juan Carlos Vázquez-Ucha
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Germán Bou
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
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11
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Carrasco LDDM, Dabul ANG, Boralli CMDS, Righetto GM, Carvalho ISE, Dornelas JV, Martins da Mata CPS, de Araújo CA, Leite EMM, Lincopan N, Camargo ILBDC. Polymyxin Resistance Among XDR ST1 Carbapenem-Resistant Acinetobacter baumannii Clone Expanding in a Teaching Hospital. Front Microbiol 2021; 12:622704. [PMID: 33897637 PMCID: PMC8063854 DOI: 10.3389/fmicb.2021.622704] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 03/05/2021] [Indexed: 12/14/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogen primarily associated with multidrug-resistant nosocomial infections, for which polymyxins are the last-resort antibiotics. This study investigated carbapenem-resistant A. baumannii strains exhibiting an extensively drug-resistant (XDR) phenotype, including four isolates considered locally pan drug-resistant (LPDR), isolated from inpatients during an outbreak at a teaching hospital in Brazil. ApaI DNA macrorestriction followed by PFGE clustered the strains in three pulsotypes, named A to C, among carbapenem-resistant A. baumannii strains. Pulsotypes A and B clustered six polymyxin-resistant A. baumannii strains. MLST analysis of representative strains of pulsotypes A, B, and C showed that they belong, respectively, to sequence types ST1 (clonal complex, CC1), ST79 (CC79), and ST903. Genomic analysis of international clones ST1 and ST79 representative strains predicted a wide resistome for β-lactams, aminoglycosides, fluoroquinolones, and trimethoprim-sulfamethoxazole, with blaOXA–23 and blaOXA–72 genes encoding carbapenem resistance. Amino acid substitutions in PmrB (Thr232Ile or Pro170Leu) and PmrC (Arg125His) were responsible for polymyxin resistance. Although colistin MICs were all high (MIC ≥ 128 mg/L), polymyxin B MICs varied; strains with Pro170Leu substitution in PmrB had MICs > 128 mg/L, while those with Thr232Ile had lower MICs (16–64 mg/L), irrespective of the clone. Although the first identified polymyxin-resistant A. baumannii strain belonged to ST79, the ST1 strains were endemic and caused the outbreak most likely due to polymyxin B use. The genome comparison of two ST1 strains from the same patient, but one susceptible and the other resistant to polymyxin, revealed mutations in 28 ORFs in addition to pmrBC. The ORF codifying an acyl-CoA dehydrogenase has gained attention due to its fatty acid breakdown and membrane fluidity involvement. However, the role of these mutations in the polymyxin resistance mechanism remains unknown. To prevent the dissemination of XDR bacteria, the hospital infection control committee implemented the patient bathing practice with a 2% chlorhexidine solution, a higher concentration than all A. baumannii chlorhexidine MICs. In conclusion, we showed the emergence of polymyxin resistance due to mutations in the chromosome of the carbapenem-resistant A. baumannii ST1, a high-risk global clone spreading in this hospital.
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Affiliation(s)
- Letícia Dias de Melo Carrasco
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Andrei Nicoli Gebieluca Dabul
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Camila Maria Dos Santos Boralli
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Gabriela Marinho Righetto
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Iago Silva E Carvalho
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | - Janaína Valerini Dornelas
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
| | | | | | | | - Nilton Lincopan
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Ilana Lopes Baratella da Cunha Camargo
- Laboratory of Molecular Epidemiology and Microbiology, Department of Physics and Interdisciplinary Science, São Carlos Institute of Physics, University of São Paulo, São Paulo, Brazil
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12
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Govender R, Amoah ID, Kumari S, Bux F, Stenström TA. Detection of multidrug resistant environmental isolates of acinetobacter and Stenotrophomonas maltophilia: a possible threat for community acquired infections? JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2020; 56:213-225. [PMID: 33378222 DOI: 10.1080/10934529.2020.1865747] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 12/10/2020] [Accepted: 12/12/2020] [Indexed: 06/12/2023]
Abstract
Acinetobacter spp. and Stenotrophomonas maltophilia are bacteria commonly associated with infections at the clinical settings. Reports of infections caused by environmental isolates are rare. Therefore, this study focused on determination of the antibiotic resistance patterns, antibiotic resistance genes, efflux pumps and virulence signatures of Acinetobacter spp. and S. maltophilia recovered from river water, plant rhizosphere and river sediment samples. The isolates were identified and confirmed using biochemical tests and PCR. The antimicrobial resistance profiles of the isolates were determined using Kirby Bauer disk diffusion assay and presence of antibiotic resistance and virulence genes were detected using PCR. S. maltophilia was more frequent in plant rhizosphere and sediment samples than the water samples. Acinetobacter spp. were mostly resistant to trimethoprim-sulfamethoxazole (96% of isolates), followed by polymyxin b (86%), cefixime (54%), colistin (42%), ampicillin (35%) and meropenem (19%). The S. maltophilia isolates displayed total resistance (100%) to trimethoprim- sulfamethoxazole, meropenem, imipenem, ampicillin and cefixime, while 80% of the isolates were resistant to ceftazidime. Acinetobacter spp. contained different antibiotic resistance genes such as sul1 (24% of isolates), sul2 (29%), blaOXA 23/51 (21%) and blaTEM (29%), while S. maltophilia harbored sul1 (8%) and blaTEM (20%). Additionally, efflux pump genes were present in all S. maltophilia isolates. The presence of multidrug resistant Acinetobacter spp. and Stenotrophomonas maltophilia in surface water raises concerns for community-acquired infections as this water is directly been used by the community for various purposes. Therefore, there is the need to institute measures aimed at reducing the risks of these infections and the resulting burden this may have on the health care system within the study area.
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Affiliation(s)
- Reshme Govender
- Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Isaac D Amoah
- Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Sheena Kumari
- Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Faizal Bux
- Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Thor A Stenström
- Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
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13
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Sharma S, Banerjee T, Yadav G, Palandurkar K. Mutations at Novel Sites in pmrA/B and lpxA/D Genes and Absence of Reduced Fitness in Colistin-Resistant Acinetobacter baumannii from a Tertiary Care Hospital, India. Microb Drug Resist 2020; 27:628-636. [PMID: 33085934 DOI: 10.1089/mdr.2020.0023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Background: Colistin resistance in Acinetobacter baumannii, the last resort drug for serious infections, is emerging worldwide. There has been paucity of data on this aspect from India, which is one of the largest producers of colistin. We studied colistin resistance in A. baumannii and characterized the isolates with respect to resistance mechanisms and virulence. Methods: A total of 365 A. baumannii isolates were studied. Antimicrobial susceptibility testing was performed as per standards. Colistin resistance mechanisms were studied by mutation detection in pmrA/B and lpxA/C/D genes, phenotypic loss of lipopolysaccharide, presence of mcr1-5 genes, and carbonyl cyanide 3-chlorophenylhydrazone (CCCP) effects. Biofilm formation, desiccation survival, and growth kinetics were studied and statistically analyzed for colistin-resistant and colistin-susceptible isolates. Results: All the colistin-resistant isolates (9, 2.5%) showed multiple mutations at novel sites in pmrA/B and/or lpxA/D genes with reversion of resistance with CCCP. Majority of these isolates (6, 66.6%) were from patients without prior colistin therapy. All received prior carbapenems. The resistant isolates demonstrated no significant difference in biofilm formation and desiccation survival but were slow growers. Conclusion: Mutations in pmrA/B and/or lpxA/D genes were the main resistance mechanism in these colistin-resistant isolates that showed no reduction in fitness.
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Affiliation(s)
- Swati Sharma
- Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Tuhina Banerjee
- Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Ghanshyam Yadav
- Department of Anesthesiology, and Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Kamlesh Palandurkar
- Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
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14
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Potron A, Vuillemenot JB, Puja H, Triponney P, Bour M, Valot B, Amara M, Cavalié L, Bernard C, Parmeland L, Reibel F, Larrouy-Maumus G, Dortet L, Bonnin RA, Plésiat P. ISAba1-dependent overexpression of eptA in clinical strains of Acinetobacter baumannii resistant to colistin. J Antimicrob Chemother 2020; 74:2544-2550. [PMID: 31199431 DOI: 10.1093/jac/dkz241] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 04/18/2019] [Accepted: 05/08/2019] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Colistin resistance in Acinetobacter baumannii often results from mutational activation of the two-component system PmrAB and subsequent addition of phospho-ethanolamine (pEtN) to lipooligosaccharide by up-regulated pEtN transferase PmrC. OBJECTIVES To characterize mechanisms of colistin resistance independent of PmrCAB in A. baumannii. METHODS Twenty-seven colistin-resistant A. baumannii were collected from 2012 to 2018. Analysis of operon pmrCAB was performed by PCR and sequencing. Seven strains were investigated further by WGS and whole-genome MLST (wgMLST). RESULTS Seven out of the 27 selected isolates were found to overexpress eptA, a gene homologous to pmrC, likely as a consequence of upstream insertion of an ISAba1 element. Insertion sites of ISAba1 were mapped 13, 18 and 156 bp ahead of the start codon of eptA in five strains, one strain and one strain, respectively. The finding that the isolates did not cluster together when compared by wgMLST analysis supports the notion that distinct insertion events occurred in close, but different, genetic backgrounds. CONCLUSIONS Activation of eptA and subsequent addition of pEtN to the cell surface represents a novel mechanism of resistance to colistin in A. baumannii.
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Affiliation(s)
- Anaïs Potron
- French National Reference Centre for Antibiotic Resistance, University Hospital of Besançon, Besançon, France.,UMR6249, CNRS Chrono-Environnement, Franche-Comté University, Besançon, France
| | | | - Hélène Puja
- UMR6249, CNRS Chrono-Environnement, Franche-Comté University, Besançon, France
| | - Pauline Triponney
- French National Reference Centre for Antibiotic Resistance, University Hospital of Besançon, Besançon, France
| | - Maxime Bour
- French National Reference Centre for Antibiotic Resistance, University Hospital of Besançon, Besançon, France
| | - Benoit Valot
- UMR6249, CNRS Chrono-Environnement, Franche-Comté University, Besançon, France
| | | | | | | | | | | | - Gerald Larrouy-Maumus
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, UK
| | - Laurent Dortet
- EA7361 'Structure, Dynamic, Function and Expression of Broad Spectrum β-Lactamases', Paris-Sud University, LabEx Lermit, Faculty of Medicine, Le Kremlin-Bicêtre, France.,French National Reference Centre for Antibiotic Resistance, Associate Laboratory, Le Kremlin-Bicêtre, France
| | - Rémy A Bonnin
- EA7361 'Structure, Dynamic, Function and Expression of Broad Spectrum β-Lactamases', Paris-Sud University, LabEx Lermit, Faculty of Medicine, Le Kremlin-Bicêtre, France.,French National Reference Centre for Antibiotic Resistance, Associate Laboratory, Le Kremlin-Bicêtre, France
| | - Patrick Plésiat
- French National Reference Centre for Antibiotic Resistance, University Hospital of Besançon, Besançon, France.,UMR6249, CNRS Chrono-Environnement, Franche-Comté University, Besançon, France
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15
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Vázquez-Ucha JC, Martínez-Guitián M, Lasarte-Monterrubio C, Conde-Pérez K, Arca-Suárez J, Álvarez-Fraga L, Pérez A, Crecente-Campo J, Alonso MJ, Bou G, Poza M, Beceiro A. Syzygium aromaticum (clove) and Thymus zygis (thyme) essential oils increase susceptibility to colistin in the nosocomial pathogens Acinetobacter baumannii and Klebsiella pneumoniae. Biomed Pharmacother 2020; 130:110606. [PMID: 32795924 DOI: 10.1016/j.biopha.2020.110606] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/30/2020] [Accepted: 08/02/2020] [Indexed: 01/29/2023] Open
Abstract
The discovery of new antibiotics that are effective against Acinetobacter baumannii and Enterobacteralesis a research priority. Several essential oils (EOs) have displayed some antimicrobial activity and could potentially act as antibiotic adjuvants. Research in this area aims to develop new therapeutic alternatives to treat infections caused by these pathogens. MICs of different EOs were determined against A. baumannii and Klebsiella pneumoniae. Combined disk diffusion tests and checkerboard assays were used to study the synergy between the EOs and antibiotics. The fractional inhibitory concentration index (FICindex) was calculated in order to categorize the interaction. Time-kill assays were also performed. The EOs that displayed the highest levels of antimicrobial activity were clove (Syzygium aromaticum L.) and thyme (Thymus zygis L.). Combined disk diffusion tests and checkerboard assays revealed synergy between these EOs and colistin. Addition of either clove or thyme EO decreased the MIC of colistin by 8- to 64-fold and 8- to 128-fold in the colistin-resistant A. baumannii and K. pneumoniae strains, respectively (FICindex ≤ 0.5, synergy). MICs were also reduced in the colistin-susceptible strains. Time-kill assays also indicated the strong activity of the combined therapy. In summary, the use of clove or thyme EO in combination with colistin could improve the efficacy of the antibiotic and significantly reduce the concentrations needed to inhibit growth of A. baumannii and K. pneumoniae.
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Affiliation(s)
- Juan C Vázquez-Ucha
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain.
| | - Marta Martínez-Guitián
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Cristina Lasarte-Monterrubio
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Jorge Arca-Suárez
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Astrid Pérez
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - José Crecente-Campo
- Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), Campus Vida Universidade de Santiago de Compostela (USC), Av. Barcelona, 15706, Santiago de Compostela, Spain
| | - María J Alonso
- Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), Campus Vida Universidade de Santiago de Compostela (USC), Av. Barcelona, 15706, Santiago de Compostela, Spain
| | - Germán Bou
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC-CICA), Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias 84, 15006, A Coruña, Spain
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16
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Karakonstantis S. A systematic review of implications, mechanisms, and stability of in vivo emergent resistance to colistin and tigecycline in Acinetobacter baumannii. J Chemother 2020; 33:1-11. [PMID: 32677578 DOI: 10.1080/1120009x.2020.1794393] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The potential of A. baumannii for acquired resistance to last resort antibiotics (colistin and tigecycline) during treatment has important clinical implications, especially when dealing with patients failing to improve despite treatment with an active antimicrobial. However, the relevant literature remains scattered. Therefore, a systematic search was conducted in PubMed and Scopus. Several studies reported emergence of resistance to colistin or tigecycline during treatment, in most cases (86%) resulting in persistent or recurrent infections, especially in cases of emergent resistance without fitness cost. Lipopolysaccharide modification in the case of colistin and overexpression of efflux pumps in the case of tigecycline were the main mechanisms of resistance. Emergent colistin resistance is often associated with fitness cost which may result in re-emergence of the fitter and more virulent colistin susceptible strain after cessation of antibiotic pressure. Prospective studies are needed to determine the frequency of emergent resistance during treatment and its impact on patient outcomes.
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Affiliation(s)
- Stamatis Karakonstantis
- Internal Medicine Department, General Hospital of Heraklion Venizeleio, Heraklion, Crete, Greece.,School of medicine, University of Crete, Heraklion, Crete, Greece
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17
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Karakonstantis S, Saridakis I. Colistin heteroresistance in Acinetobacter spp.: systematic review and meta-analysis of the prevalence and discussion of the mechanisms and potential therapeutic implications. Int J Antimicrob Agents 2020; 56:106065. [PMID: 32599229 DOI: 10.1016/j.ijantimicag.2020.106065] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/30/2020] [Accepted: 06/20/2020] [Indexed: 01/29/2023]
Abstract
BACKGROUND Colistin is one of the few remaining options for carbapenem-resistant Acinetobacter baumannii (A. baumannii); however, emergence of resistance from heteroresistant populations is possible. This review aimed to systematically search and consolidate the literature on the prevalence, mechanisms and therapeutic implications of colistin heteroresistance in Acinetobacter spp. METHODS A systematic search was conducted in PubMed and Scopus. The pooled prevalence of colistin heteroresistance was calculated using meta-analysis of proportions with the Freeman-Tukey transformation and the random-effects (DerSimonian and Laird) method. RESULTS Based on 15 studies the prevalence of colistin heteroresistance was 33% (95% CI 16-53%) but considerable heterogeneity was observed (I2 = 96%, P < 0.001). Prior exposure to colistin was associated with a higher proportion of resistant subpopulations. Colistin heteroresistance may result from chromosomal mutations in resistant subpopulations (predominantly in PmrAB and lpx genes) resulting in lipopolysaccharide modification or loss, or overexpression of efflux pumps. No dosage scheme of colistin monotherapy can prevent the emergence of resistant subpopulations in vitro, but few studies have reported in vivo emergence of resistance from heteroresistant A. baumannii during treatment, and studies examining the correlation between heteroresistance and clinical/microbiological outcomes are lacking. Several colistin-based combinations have been shown in vitro to prevent the emergence of the resistant subpopulations but none have been translated so far into clinical benefit. Reasons for this discrepancy are discussed. CONCLUSIONS Colistin heteroresistance was common but highly variable between studies. The impact of colistin heteroresistance (frequency of emergent resistance during treatment and correlation with treatment outcomes) requires further study.
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Affiliation(s)
- Stamatis Karakonstantis
- School of Medicine, University of Crete, Heraklion, Crete, Greece; Internal Medicine Department, General Hospital of Heraklion Venizeleio, Heraklion, Crete, Greece.
| | - Ioannis Saridakis
- Internal Medicine Department, General Hospital of Heraklion Venizeleio, Heraklion, Crete, Greece
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18
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Choi Y, Lee JY, Lee H, Park M, Kang K, Lim SK, Shin D, Ko KS. Comparison of Fitness Cost and Virulence in Chromosome- and Plasmid-Mediated Colistin-Resistant Escherichia coli. Front Microbiol 2020; 11:798. [PMID: 32477288 PMCID: PMC7238749 DOI: 10.3389/fmicb.2020.00798] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 04/03/2020] [Indexed: 12/13/2022] Open
Abstract
Five types of Escherichia coli strains were obtained and sequenced: colistin-susceptible (CL-S) strains, in vitro induced colistin-resistant (CL-IR) strains, mcr-1-negative colistin-resistant strains from livestock (CL-chrR), mcr-1-positive colistin-resistant strains (CL-mcrR), and mcr-1-transferred transconjugants (TC-mcr). Amino acid alterations of PmrAB, PhoPQ, and EptA were identified, and their mRNA expression was measured. Their growth rate was evaluated, and an in vitro competition assay was performed. Virulence was compared through serum resistance and survival in macrophages and Drosophila melanogaster. CL-IR and CL-chrR strains were colistin-resistant due to amino acid alterations in PmrAB, PhoPQ, or EptA, and their overexpression. All colistin-resistant strains did not show reduced growth rates compared with CL-S strains. CL-IR and CL-chrR strains were less competitive than the susceptible strain, but CL-mcrR strains were not. In addition, TC-mcr strains were also significantly more competitive than their respective parental susceptible strain. CL-IR strains had similar or decreased survival rates in human serum, macrophages, and fruit flies, compared with their parental, susceptible strains. CL-chrR strains were also less virulent than CL-S strains. Although CL-mcrR strains showed similar survival rates in human serum and fruit fly to CL-S strains, the survival rates of TC-mcr strains decreased significantly in human serum, macrophages, and fruit flies, compared with their susceptible recipient strain (J53). Chromosome-mediated, colistin-resistant E. coli strains have a fitness cost, but plasmids bearing mcr-1 do not increase the fitness burden of E. coli. Along with high usage of polymyxins, the no fitness cost of mcr-1-positive strains may facilitate rapid spread of colistin resistance.
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Affiliation(s)
- Yujin Choi
- Department of Microbiology, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Ji-Young Lee
- Division of Antimicrobial Resistance, Korea Centers for Disease Control and Prevention, Cheongju, South Korea
| | - Haejeong Lee
- Department of Microbiology, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Myungseo Park
- Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, South Korea
| | - KyeongJin Kang
- Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Suk-Kyung Lim
- Bacterial Disease Division, Animal and Plant Quarantine Agency, Gimcheon, South Korea
| | - Dongwoo Shin
- Department of Microbiology, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Kwan Soo Ko
- Department of Microbiology, Sungkyunkwan University School of Medicine, Suwon, South Korea
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19
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Huang J, Li C, Song J, Velkov T, Wang L, Zhu Y, Li J. Regulating polymyxin resistance in Gram-negative bacteria: roles of two-component systems PhoPQ and PmrAB. Future Microbiol 2020; 15:445-459. [PMID: 32250173 DOI: 10.2217/fmb-2019-0322] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Polymyxins (polymyxin B and colistin) are last-line antibiotics against multidrug-resistant Gram-negative pathogens. Polymyxin resistance is increasing worldwide, with resistance most commonly regulated by two-component systems such as PmrAB and PhoPQ. This review discusses the regulatory mechanisms of PhoPQ and PmrAB in mediating polymyxin resistance, from receiving an external stimulus through to activation of genes responsible for lipid A modifications. By analyzing the reported nonsynonymous substitutions in each two-component system, we identified the domains that are critical for polymyxin resistance. Notably, for PmrB 71% of resistance-conferring nonsynonymous mutations occurred in the HAMP (present in histidine kinases, adenylate cyclases, methyl accepting proteins and phosphatase) linker and DHp (dimerization and histidine phosphotransfer) domains. These results enhance our understanding of the regulatory mechanisms underpinning polymyxin resistance and may assist with the development of new strategies to minimize resistance emergence.
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Affiliation(s)
- Jiayuan Huang
- Biomedicine Discovery Institute & Department of Microbiology, Monash University, Melbourne 3800, Australia
| | - Chen Li
- Biomedicine Discovery Institute & Department of Biochemistry & Molecular Biology, Monash University, Melbourne 3800, Australia.,Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich 8093, Switzerland
| | - Jiangning Song
- Biomedicine Discovery Institute & Department of Biochemistry & Molecular Biology, Monash University, Melbourne 3800, Australia
| | - Tony Velkov
- Department of Pharmacology & Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry & Health Sciences, The University of Melbourne, Melbourne 3010, Australia
| | - Lushan Wang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Yan Zhu
- Biomedicine Discovery Institute & Department of Microbiology, Monash University, Melbourne 3800, Australia
| | - Jian Li
- Biomedicine Discovery Institute & Department of Microbiology, Monash University, Melbourne 3800, Australia
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20
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Acquisition of Colistin Resistance Links Cell Membrane Thickness Alteration with a Point Mutation in the lpxD Gene in Acinetobacter baumannii. Antibiotics (Basel) 2020; 9:antibiotics9040164. [PMID: 32268563 PMCID: PMC7235794 DOI: 10.3390/antibiotics9040164] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 04/01/2020] [Accepted: 04/02/2020] [Indexed: 02/04/2023] Open
Abstract
Acinetobacter baumannii is one of the most common causes of nosocomial infections in intensive care units. Its ability to acquire diverse mechanisms of resistance limits the therapeutic choices for its treatment. This especially concerns colistin, which has been reused recently as a last-resort drug against A. baumannii. Here, we explored the impact of gaining colistin resistance on the susceptibility of A. baumannii to other antibiotics and linked colistin resistance acquisition to a gene mutation in A. baumannii. The susceptibility of 95 A. baumannii isolates revealed that 89 isolates were multi-drug resistance (MDR), and nine isolates were resistant to colistin. Subsequently, three isolates, i.e., MS48, MS50, and MS64, exhibited different resistance patterns when colistin resistance was induced and gained resistance to almost all tested antibiotics. Upon TEM examination, morphological alterations were reported for all induced isolates and a colistin-resistant clinical isolate (MS34Col-R) compared to the parental sensitive strains. Finally, genetic alterations in PmrB and LpxACD were assessed, and a point mutation in LpxD was identified in the MS64Col-R and MS34Col-R mutants, corresponding to Lys117Glu substitution in the lipid-binding domain. Our findings shed light on the implications of using colistin in the treatment of A. baumannii, especially at sub-minimum inhibitory concentrations concentrations, since cross-resistance to other classes of antibiotics may emerge, beside the rapid acquisition of resistance against colistin itself due to distinct genetic events.
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21
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Gerson S, Lucaßen K, Wille J, Nodari CS, Stefanik D, Nowak J, Wille T, Betts JW, Roca I, Vila J, Cisneros JM, Seifert H, Higgins PG. Diversity of amino acid substitutions in PmrCAB associated with colistin resistance in clinical isolates of Acinetobacter baumannii. Int J Antimicrob Agents 2019; 55:105862. [PMID: 31837449 DOI: 10.1016/j.ijantimicag.2019.105862] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 12/02/2019] [Accepted: 12/08/2019] [Indexed: 11/18/2022]
Abstract
This study aimed to investigate the mechanisms of colistin resistance in 64 Acinetobacter baumannii isolates obtained from patients with ventilator-associated pneumonia hospitalised in Greece, Italy and Spain. In total, 31 A. baumannii isolates were colistin-resistant. Several novel amino acid substitutions in PmrCAB were found in 27 colistin-resistant A. baumannii. Most substitutions were detected in PmrB, indicating the importance of the histidine kinase for colistin resistance. In two colistin-resistant isolates, 93 amino acid changes were observed in PmrCAB compared with A. baumannii ACICU, and homologous recombination across different clonal lineages was suggested. Analysis of gene expression revealed increased pmrC expression in isolates harbouring pmrCAB mutations. Complementation of A. baumannii ATCC 19606 and ATCC 17978 with a pmrAB variant revealed increased pmrC expression but unchanged colistin MICs, indicating additional unknown factors associated with colistin resistance. Moreover, a combination of PmrB and PmrC alterations was associated with very high colistin MICs, suggesting accumulation of mutations as the mechanism for high-level resistance. The pmrC homologue eptA was detected in 29 colistin-susceptible and 26 colistin-resistant isolates. ISAba1 was found upstream of eptA in eight colistin-susceptible and one colistin-resistant isolate and eptA was disrupted by ISAba125 in two colistin-resistant isolates. Whilst in most isolates an association of eptA with colistin resistance was excluded, in one isolate an amino acid substitution in EptA (R127L) combined with a point mutation in ISAba1 upstream of eptA contributed to elevated colistin MICs. This study helps to gain an insight into the diversity and complexity of colistin resistance in A. baumannii.
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Affiliation(s)
- Stefanie Gerson
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany
| | - Kai Lucaßen
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany
| | - Julia Wille
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany; German Center for Infection Research (DZIF), partner site Bonn-Cologne, Germany
| | - Carolina S Nodari
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany; Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine, Escola Paulista de Medicina (EPM), São Paulo, Brazil
| | - Danuta Stefanik
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany
| | - Jennifer Nowak
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany
| | - Thorsten Wille
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany
| | - Jonathan W Betts
- School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Ignasi Roca
- Department of Clinical Microbiology and ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Spain
| | - Jordi Vila
- Department of Clinical Microbiology and ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Spain
| | - Jose M Cisneros
- Department of Infectious Diseases, Microbiology, and Preventive Medicine, Infectious Diseases Research Group, Institute of Biomedicine of Seville (IBiS), University of Seville/CSIC/University Hospital Virgen del Rocío, Seville, Spain
| | - Harald Seifert
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany; German Center for Infection Research (DZIF), partner site Bonn-Cologne, Germany
| | - Paul G Higgins
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany; German Center for Infection Research (DZIF), partner site Bonn-Cologne, Germany.
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Discrepancies in susceptibility testing to colistin in Acinetobacter baumannii: The influence of slow growth and heteroresistance. Int J Antimicrob Agents 2019; 54:587-591. [DOI: 10.1016/j.ijantimicag.2019.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/28/2019] [Accepted: 08/01/2019] [Indexed: 01/02/2023]
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23
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Sequential emergence of colistin and rifampicin resistance in an OXA-72- producing outbreak strain of Acinetobacter baumannii. Int J Antimicrob Agents 2019; 53:669-673. [DOI: 10.1016/j.ijantimicag.2019.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/21/2018] [Accepted: 01/21/2019] [Indexed: 11/24/2022]
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24
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Investigation of Novel pmrB and eptA Mutations in Isogenic Acinetobacter baumannii Isolates Associated with Colistin Resistance and Increased Virulence In Vivo. Antimicrob Agents Chemother 2019; 63:AAC.01586-18. [PMID: 30617096 DOI: 10.1128/aac.01586-18] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 12/05/2018] [Indexed: 12/19/2022] Open
Abstract
Colistin resistance in Acinetobacter baumannii is of great concern and is a threat to human health. In this study, we investigate the mechanisms of colistin resistance in four isogenic pairs of A. baumannii isolates displaying an increase in colistin MICs. A mutation in pmrB was detected in each colistin-resistant isolate, three of which were novel (A28V, I232T, and ΔL9-G12). Increased expression of pmrC was shown by semi-quantitative reverse transcription-PCR (qRT-PCR) for three colistin-resistant isolates, and the addition of phosphoethanolamine (PEtN) to lipid A by PmrC was revealed by mass spectrometry. Interestingly, PEtN addition was also observed in some colistin-susceptible isolates, indicating that this resistance mechanism might be strain specific and that other factors could contribute to colistin resistance. Furthermore, the introduction of pmrAB carrying the short amino acid deletion ΔL9-G12 into a pmrAB knockout strain resulted in increased pmrC expression and lipid A modification, but colistin MICs remained unchanged, further supporting the strain specificity of this colistin resistance mechanism. Of note, a mutation in the pmrC homologue eptA and a point mutation in ISAba1 upstream of eptA were associated with colistin resistance and increased eptA expression, which is a hitherto undescribed resistance mechanism. Moreover, no cost of fitness was observed for colistin-resistant isolates, while the virulence of these isolates was increased in a Galleria mellonella infection model. Although the mutations in pmrB were associated with colistin resistance, PEtN addition appears not to be the sole factor leading to colistin resistance, indicating that the mechanism of colistin resistance is far more complex than previously suspected and is potentially strain specific.
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25
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Cafiso V, Stracquadanio S, Lo Verde F, Gabriele G, Mezzatesta ML, Caio C, Pigola G, Ferro A, Stefani S. Colistin Resistant A. baumannii: Genomic and Transcriptomic Traits Acquired Under Colistin Therapy. Front Microbiol 2019; 9:3195. [PMID: 30666237 PMCID: PMC6330354 DOI: 10.3389/fmicb.2018.03195] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 12/10/2018] [Indexed: 12/31/2022] Open
Abstract
Even though colistin-based treatment represents the antimicrobial-regimen backbone for the management of multidrug-resistant Gram-negative infections, colistin resistance is still rare, at least as a full resistance, in Acinetobacter baumannii (Ab). We investigated the genomics and transcriptomics of two clinical Extensively Drug Resistance (XDR) colistin-susceptible/resistant (COL-S/R) Ab strain-pairs in which COL-resistance was developed after exposure to colistin therapy. The molecular characterization of the strains showed that all strains belonged to PFGE-A, ST-281, OXA-23 producers, Global Clone-II, and were resistant to imipenem, meropenem, ampicillin/sulbactam, ciprofloxacin, gentamicin, amikacin, trimethoprim/sulfamethoxazole, and susceptible to tigecycline, in agreement with NGS-acquired resistome. COL-R vs. COL-S Ab comparative genomics, mapping on Ab ATCC 17978 and Ab ACICU Reference Genomes, revealed a closely related genomic phylogeny, especially between strain-pair isolates, and distinctive common genomic non-synonymous SNPs (nsSNPs) in COL-R Ab strains. Furthermore, pmrB and pmrC nsSNPs were found. Notably we recovered, for the first time, lpxC and lpxD nsSNPs previously described only in "in-vitro" mutants and associated with colistin resistance in a clinical COL-R Ab. COL-R vs. COL-S Ab comparative transcriptomics evidenced a strain-dependent response to the colistin resistance onset highly variable among the single COL-R strains vs. their COL-S parents and merely seven common over-expressed transcripts, i.e. the PgaB lipoprotein for biofilm-matrix production, the diacylglycerol kinase for the lipid recycling in the membrane-derived oligosaccharide cycle, a membrane non-ribosomal peptide synthetase, the Lipid A phosphoethanol aminotransferase PmrC, and three hypothetical proteins. The transcript analysis of the "COL-R related genes" and the RNA-seq data confirmed pmrCAB over-expression responsible for a greater positive net cell-charge, and lpxACD under-expression in COL-R causing a decreased LPS production, as main mechanisms of colistin resistance. Our study reports the COL-R Ab genomic and transcriptomic signatures reflecting the interplay between several direct and indirect potential adaptations to antimicrobial pressure, including the occurrence of SNP accumulation hotspot loci in genes related to intrinsic or adaptive colistin resistance, surface adhesion proteins and porins, and over-expressed genes involved in different pathways, i.e. biofilm production, oxidative stress response, extensive drug and COL resistance.
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Affiliation(s)
- Viviana Cafiso
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Stefano Stracquadanio
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Flavia Lo Verde
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Giacoma Gabriele
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Maria Lina Mezzatesta
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Carla Caio
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Giuseppe Pigola
- Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Alfredo Ferro
- Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Stefania Stefani
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
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26
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Uddin R, Masood F, Azam SS, Wadood A. Identification of putative non-host essential genes and novel drug targets against Acinetobacter baumannii by in silico comparative genome analysis. Microb Pathog 2018; 128:28-35. [PMID: 30550846 DOI: 10.1016/j.micpath.2018.12.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 12/10/2018] [Accepted: 12/10/2018] [Indexed: 10/27/2022]
Abstract
Acinetobacter baumannii, the gram-negative bacteria emerged as an extremely critical pathogen causing nosocomial and different kinds of infections. A. baumannii exhibit resistivity towards various classes of antibiotics that shows that there is a dire need to search more drug targets by exploiting the full genome of the bacteria. In doing so, a strategy is made with the combination of computational biology, pathogen informatics and cheminformatics. Comparative genomics analysis, modeling and docking studies have been performed for the prediction of non-host essential genes and novel drug candidates against A. baumannii. Among 37 unique and 82 common metabolic pathways, 92 genes were predicted as non-host genes. Similarly, using homology search between A. baumannii genome and essential genes of different bacteria, 293 genes were predicted as essential genes of A. baumannii. Among these predicted non-host and essential genes, 86 genes were predicted as non-host essential genes which could serve as potential novel drug and vaccine targets. Additional drug-target like physicochemical properties were estimated such as the molecular weight, subcellular localization and druggability potential. On the structural part, the crystal structures of all the non-host essential genes of A. baumannii were found except the three genes. Out of these three, a homology model of Undecaprenyl-diphosphatase was built using a PDB template by MODELLER [version 9.18]. The quality of the model was assessed by the ProSA and RAMPAGE. The built model was subjected as a receptor for the molecular docking with Adenosine diphosphate (ADP) as a ligand. The molecular docking was performed by AutoDock4 and the best conformation with lowest binding energy (-4.39 kcal/mol) was obtained. The LigPlot was used to identify the close interactions between the ligand the receptor's residues. This study will further aid for the selection of putative inhibitors against a novel drug target identified against A. baumannii and hence could lead to the better therapeutics.
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Affiliation(s)
- Reaz Uddin
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Pakistan.
| | - Fareha Masood
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Pakistan
| | - Syed Sikander Azam
- National Centre for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Abdul Wadood
- Department of Biochemistry, Abdul Wali Khan University, Mardan, Pakistan
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27
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Molecular mechanisms of polymyxin resistance and detection of mcr genes. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2018; 163:28-38. [PMID: 30439931 DOI: 10.5507/bp.2018.070] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 10/26/2018] [Indexed: 12/12/2022] Open
Abstract
Antibiotic resistance is an ever-increasing global problem. Major commercial antibiotics often fail to fight common bacteria, and some pathogens have become multi-resistant. Polymyxins are potent bactericidal antibiotics against gram-negative bacteria. Known resistance to polymyxin includes intrinsic, mutational and adaptive mechanisms, with the recently described horizontally acquired resistance mechanisms. In this review, we present several strategies for bacteria to develop enhanced resistance to polymyxins, focusing on changes in the outer membrane, efflux and other resistance determinants. Better understanding of the genes involved in polymyxin resistance may pave the way for the development of new and effective antimicrobial agents. We also report novel in silico tested primers for PCR assay that may be able distinguish colistin-resistant isolates carrying the plasmid-encoded mcr genes and will assist in combating the spread of colistin resistance in bacteria.
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28
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Carretero-Ledesma M, García-Quintanilla M, Martín-Peña R, Pulido MR, Pachón J, McConnell MJ. Phenotypic changes associated with Colistin resistance due to Lipopolysaccharide loss in Acinetobacter baumannii. Virulence 2018; 9:930-942. [PMID: 29638177 PMCID: PMC5955468 DOI: 10.1080/21505594.2018.1460187] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acinetobacter baumannii can acquire resistance to colistin via complete loss of lipopolysaccharide (LPS) biosynthesis due to mutations in the lpxA, lpxC and lpxD genes. However, although colistin is increasingly being used for the treatment of multidrug resistant infections, very few A. baumannii clinical isolates develop colistin resistance through loss of LPS biosynthesis. This may suggest that LPS loss affects virulence traits that play a role in the transmission and pathogenesis of A. baumannii. In this study we characterize multiple virulence phenotypes of colistin resistant, LPS-deficient derivatives of the ATCC 19606 strain and five multidrug resistant clinical isolates and their colistin resistant, LPS-deficient derivatives. Our results indicate that LPS loss results in growth defects compared to the parental strain in vitro both in laboratory media and human serum (competition indices of 0.58 and 7.0 × 10−7, respectively) and reduced ability to grow and disseminate in vivo (competition index 6.7 × 10−8). Infection with the LPS-deficient strain resulted in lower serum levels of pro-inflammatory cytokines TNF-α and IL-6 compared to the parent strain, and was less virulent in a mouse model of disseminated sepsis. LPS loss also significantly affected biofilm production, surface motility, growth under iron limitation and susceptibility to multiple disinfectants used in the clinical setting. These results demonstrate that LPS loss has a significant effect on multiple virulence traits, and may provide insight into the low incidence of colistin resistant strains lacking LPS that have been reported in the clinical setting.
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Affiliation(s)
- Marta Carretero-Ledesma
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain
| | - Meritxell García-Quintanilla
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain
| | - Reyes Martín-Peña
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain
| | - Marina R Pulido
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain
| | - Jerónimo Pachón
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain.,b Department of Medicine , University of Seville , Seville , Spain
| | - Michael J McConnell
- a Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine; Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC /University of Seville , Seville , Spain
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29
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Colistin Heteroresistance and Involvement of the PmrAB Regulatory System in Acinetobacter baumannii. Antimicrob Agents Chemother 2018; 62:AAC.00788-18. [PMID: 29914966 DOI: 10.1128/aac.00788-18] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 06/14/2018] [Indexed: 02/08/2023] Open
Abstract
Multidrug-resistant Acinetobacter baumannii infection has recently emerged as a worldwide clinical problem, and colistin is increasingly being used as a last-resort therapy. Despite its favorable bacterial killing, resistance and heteroresistance (HR) to colistin have been described. The purpose of the present study was to investigate the role of the PmrAB regulatory pathway in laboratory-selected mutants representative of global epidemic strains. From three unrelated A. baumannii clinical strains (sequence types 2, 3, and 20), eight colistin-resistant mutants were selected. Half of the mutants showed HR to colistin according to the reference method (population analysis profiling), whereas the other half exhibited stable resistance. M12I mutation within pmrA and M308R, S144KLAGS, and P170L mutations for pmrB were associated with HR to colistin, while T235I, A226T, and P233S mutations within pmrB were associated with stable resistance. The transcript levels of the pmrCAB operon were upregulated in all the mutants. Compensatory mutations were explored for some mutants. A single mutant (T235I mutant) displayed a compensatory mutation through ISAba1 mobilization within the pmrB gene that was associated with the loss of colistin resistance. The mutant resistance phenotype associated with T235I was partially restored in a trans-complementation assay turning to HR. The level of colistin resistance was correlated with the level of expression of pmrC in the trans-complemented strains. This report shows the role of different mutations in the PmrAB regulatory pathway and warns of the development of colistin HR that could be present but not easily detected through routine testing.
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30
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Emergence of High-Level Colistin Resistance in an Acinetobacter baumannii Clinical Isolate Mediated by Inactivation of the Global Regulator H-NS. Antimicrob Agents Chemother 2018; 62:AAC.02442-17. [PMID: 29712662 DOI: 10.1128/aac.02442-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/01/2018] [Indexed: 12/31/2022] Open
Abstract
Colistin is a crucial last-line drug used for the treatment of life-threatening infections caused by multidrug-resistant strains of the Gram-negative bacterium Acinetobacter baumannii However, colistin-resistant A. baumannii isolates can still be isolated following failed colistin therapy. Resistance is most often mediated by the addition of phosphoethanolamine (pEtN) to lipid A by PmrC, following missense mutations in the pmrCAB operon encoding PmrC and the two-component signal transduction system PmrA/PmrB. We recovered a pair of A. baumannii isolates from a single patient before (6009-1) and after (6009-2) failed colistin treatment. These strains displayed low and very high levels of colistin resistance (MICs, 8 to 16 μg/ml and 128 μg/ml), respectively. To understand how increased colistin resistance arose, we sequenced the genome of each isolate, which revealed that 6009-2 had an extra copy of the insertion sequence element ISAba125 within a gene encoding an H-NS family transcriptional regulator. To confirm the role of H-NS in colistin resistance, we generated an hns deletion mutant in 6009-1 and showed that colistin resistance increased upon the deletion of hns We also provided 6009-2 with an intact copy of hns and showed that the strain was no longer resistant to high concentrations of colistin. Transcriptomic analysis of the clinical isolates identified more than 150 genes as being differentially expressed in the colistin-resistant hns mutant 6009-2. Importantly, the expression of eptA, encoding a second lipid A-specific pEtN transferase but not pmrC, was increased in the hns mutant. This is the first time an H-NS family transcriptional regulator has been associated with a pEtN transferase and colistin resistance.
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31
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Lowe M, Ehlers MM, Ismail F, Peirano G, Becker PJ, Pitout JDD, Kock MM. Acinetobacter baumannii: Epidemiological and Beta-Lactamase Data From Two Tertiary Academic Hospitals in Tshwane, South Africa. Front Microbiol 2018; 9:1280. [PMID: 29946315 PMCID: PMC6005857 DOI: 10.3389/fmicb.2018.01280] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/25/2018] [Indexed: 01/26/2023] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogen that is increasingly responsible for hospital-acquired infections. The increasing prevalence of carbapenem resistant A. baumannii has left clinicians with limited treatment options. Last line antimicrobials (i.e., polymyxins and glycylcyclines) are often used as treatment options. The aim of this study was to determine the prevalence of selected β-lactamase genes from A. baumannii isolates obtained from patients with hospital-acquired infections and to determine the genetic relationship and epidemiological profiles among clinical A. baumannii isolates collected from two tertiary academic hospitals in the Tshwane region, South Africa (SA). Multiplex-PCR (M-PCR) assays were performed to detect selected resistance genes. The collected isolates’ genetic relatedness was determined by using pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The acquired oxacillinase (OXA) genes, notably blaOXA-23-like were prevalent in the A. baumannii isolates. The M-PCR assays showed that the isolates collected from hospital A contained the OXA-23-like (96%; n = 69/72) genes and the isolates collected from hospital B contained the OXA-23-like (91%; n = 63/69) and OXA-58-like (4%; n = 3/69) genes. Colistin resistance was found in 1% of the isolates (n = 2/141) and tigecycline intermediate resistance was found in 6% of the isolates (n = 8/141). The A. baumannii isolates were genetically diverse. Molecular epidemiological data showed that specific sequence types (STs) (ST106, ST229, ST258 and ST208) were established in both hospitals, while ST848 was established in hospital A and ST502, ST339 and the novel ST1552 were established in hospital B. ST848 (established in hospital A) was predominately detected in ICU wards whereas ST208, ST339 and the novel ST1552 (established in hospital B) were detected in ICUs and the general wards. The origin of the A. baumannii isolates in the hospitals may be due to the dissemination and adaptation of a diverse group of successful clones. Poor infection control and prevention strategies and possibly the overuse of antimicrobials contributed to the establishment of these A. baumannii clones in the studied hospitals.
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Affiliation(s)
- Michelle Lowe
- Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Marthie M Ehlers
- Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.,Department of Medical Microbiology, Tshwane Academic Division, National Health Laboratory Service, Pretoria, South Africa
| | - Farzana Ismail
- Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.,Department of Medical Microbiology, Tshwane Academic Division, National Health Laboratory Service, Pretoria, South Africa
| | - Gisele Peirano
- Departments of Microbiology, Immunology, Infectious Diseases and Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Division of Microbiology, Calgary Laboratory Services, Calgary, AB, Canada
| | - Piet J Becker
- Research Office, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Johann D D Pitout
- Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.,Departments of Microbiology, Immunology, Infectious Diseases and Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Division of Microbiology, Calgary Laboratory Services, Calgary, AB, Canada
| | - Marleen M Kock
- Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.,Department of Medical Microbiology, Tshwane Academic Division, National Health Laboratory Service, Pretoria, South Africa
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32
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Bahador A, Farshadzadeh Z, Raoofian R, Mokhtaran M, Pourakbari B, Pourhajibagher M, Hashemi FB. Association of virulence gene expression with colistin-resistance in Acinetobacter baumannii: analysis of genotype, antimicrobial susceptibility, and biofilm formation. Ann Clin Microbiol Antimicrob 2018; 17:24. [PMID: 29859115 PMCID: PMC5984448 DOI: 10.1186/s12941-018-0277-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/19/2018] [Indexed: 12/01/2022] Open
Abstract
Background Acinetobacter baumannii causes difficult-to-treat nosocomial infections, which often lead to morbidity due to the development of antimicrobial drug resistance and expression of virulence genes. Data regarding the association of resistance to colistin, a last treatment option, and the virulence gene expression of A. baumannii is scarce. Methods We evaluated the MLVA genotype, antimicrobial resistance, and biofilm formation of 100 A. baumannii isolates from burn patients, and further compared the in vitro and in vivo expression of four virulence genes among five colistin-resistant A. baumannii (Cst-R-AB) isolates. Five Cst-R-AB isolates were tested; one from the present study, and four isolated previously. Results Our results showed that reduced expression of recA, along with increased in vivo expression of lpsB, dnaK, and blsA; are associated with colistin resistance among Cst-R-AB isolates. Differences in virulence gene expressions among Cst-R-AB isolates, may in part explain common discrepant in vitro vs. in vivo susceptibility data during treatment of infections caused by Cst-R-AB. Conclusions Our findings highlight the intricate relationship between colistin-resistance and virulence among A. baumannii isolates, and underscore the importance of examining the interactions between virulence and antimicrobial resistance toward efforts to control the spread of multidrug-resistant A. baumannii (MDR-AB) isolates, and also to reduce disease severity in burn patients with MDR-AB infection. Electronic supplementary material The online version of this article (10.1186/s12941-018-0277-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Abbas Bahador
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina Ave., 100 Keshavarz Blvd, Tehran, 14167-53955, Iran.,Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran.,Laser Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Zahra Farshadzadeh
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina Ave., 100 Keshavarz Blvd, Tehran, 14167-53955, Iran
| | - Reza Raoofian
- Legal Medicine Research Center, Legal Medicine Organization, Tehran, Iran.,Innovative Research Center, Islamic Azad University, Mashhad Branch, Mashhad, Iran
| | - Masoumeh Mokhtaran
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina Ave., 100 Keshavarz Blvd, Tehran, 14167-53955, Iran
| | - Babak Pourakbari
- Pediatrics Infectious Disease Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Maryam Pourhajibagher
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina Ave., 100 Keshavarz Blvd, Tehran, 14167-53955, Iran.,Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Farhad B Hashemi
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, 100 Poursina Ave., 100 Keshavarz Blvd, Tehran, 14167-53955, Iran.
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33
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Nang SC, Morris FC, McDonald MJ, Han ML, Wang J, Strugnell RA, Velkov T, Li J. Fitness cost of mcr-1-mediated polymyxin resistance in Klebsiella pneumoniae. J Antimicrob Chemother 2018; 73:1604-1610. [PMID: 29514208 PMCID: PMC6693033 DOI: 10.1093/jac/dky061] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/25/2018] [Accepted: 01/30/2018] [Indexed: 12/30/2022] Open
Abstract
Objectives The discovery of mobile colistin resistance mcr-1, a plasmid-borne polymyxin resistance gene, highlights the potential for widespread resistance to the last-line polymyxins. In the present study, we investigated the impact of mcr-1 acquisition on polymyxin resistance and biological fitness in Klebsiella pneumoniae. Methods K. pneumoniae B5055 was used as the parental strain for the construction of strains carrying vector only (pBBR1MCS-5) and mcr-1 recombinant plasmids (pmcr-1). Plasmid stability was determined by serial passaging for 10 consecutive days in antibiotic-free LB broth, followed by patching on gentamicin-containing and antibiotic-free LB agar plates. Lipid A was analysed using LC-MS. The biological fitness was examined using an in vitro competition assay analysed with flow cytometry. The in vivo fitness cost of mcr-1 was evaluated in a neutropenic mouse thigh infection model. Results Increased polymyxin resistance was observed following acquisition of mcr-1 in K. pneumoniae B5055. The modification of lipid A with phosphoethanolamine following mcr-1 addition was demonstrated by lipid A profiling. The plasmid stability assay revealed the instability of the plasmid after acquiring mcr-1. Reduced in vitro biological fitness and in vivo growth were observed with the mcr-1-carrying K. pneumoniae strain. Conclusions Although mcr-1 confers a moderate level of polymyxin resistance, it is associated with a significant biological fitness cost in K. pneumoniae. This indicates that mcr-1-mediated resistance in K. pneumoniae could be attenuated by limiting the usage of polymyxins.
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Affiliation(s)
- Sue C Nang
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Faye C Morris
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Michael J McDonald
- Centre for Geometric Biology, School of Biological Sciences, Monash University, Victoria, Australia
| | - Mei-Ling Han
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Jiping Wang
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
| | - Richard A Strugnell
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria, Australia
| | - Tony Velkov
- Department of Pharmacology and Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Victoria, Australia
| | - Jian Li
- Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia
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Vourli S, Dafopoulou K, Vrioni G, Tsakris A, Pournaras S. Evaluation of two automated systems for colistin susceptibility testing of carbapenem-resistant Acinetobacter baumannii clinical isolates. J Antimicrob Chemother 2018; 72:2528-2530. [PMID: 28605445 DOI: 10.1093/jac/dkx186] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 05/19/2017] [Indexed: 11/14/2022] Open
Abstract
Background Colistin is commonly needed for the treatment of infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) and the determination of its in vitro activity is obviously important. However, the accurate routine antimicrobial susceptibility testing (AST) of colistin is still challenging. The only acceptable method for colistin AST is broth microdilution (BMD); disc and gradient diffusion assays are inappropriate and the performance of semi-automated systems has not been validated. Objectives In the present study, two commonly used semi-automated systems were evaluated for colistin AST of contemporary CRAB clinical isolates. Methods A total of 117 single-patient CRAB isolates collected randomly during 2015 from distinct tertiary hospitals located throughout Greece were tested. Colistin MICs were determined using the semi-automated systems Phoenix100 and Vitek2 and also agar dilution (AD), compared with the reference BMD. Results Colistin resistance rates for Phoenix100/Vitek2/AD/BMD were 15.4%/16.2%/35.9%/24.8%. The essential/categorical agreement rates were as follows: Phoenix100, 91.5%/88.9%; Vitek2, 88.9%/89.7%; and AD, 93.2%/87.2%. Alarmingly high rates of very major errors (VMEs) were observed for Phoenix100 (41.4%) and Vitek2 (37.9%), while major errors (MEs) were limited (1.1% by both systems); VMEs were much more common for isolates with MICs of 2 mg/L than for isolates with MICs of ≤ 1 mg/L, as determined by automated methods. AD produced considerably higher colistin MICs, yielding MEs of 15.9%. Conclusions Colistin resistance of A. baumannii is greatly underestimated by Phoenix100/Vitek2, potentially leading to inappropriate colistin administration. Colistin AST results by automated systems within the susceptible range, particularly those at the susceptibility breakpoint (2 mg/L), need to be validated by BMD.
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Affiliation(s)
- Sophia Vourli
- Laboratory of Clinical Microbiology, Attikon University Hospital, Athens, Greece
| | - Konstantina Dafopoulou
- Department of Microbiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Georgia Vrioni
- Department of Microbiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Athanassios Tsakris
- Department of Microbiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Spyros Pournaras
- Laboratory of Clinical Microbiology, Attikon University Hospital, Athens, Greece.,Department of Microbiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
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Lima WG, Alves MC, Cruz WS, Paiva MC. Chromosomally encoded and plasmid-mediated polymyxins resistance in Acinetobacter baumannii: a huge public health threat. Eur J Clin Microbiol Infect Dis 2018. [PMID: 29524060 DOI: 10.1007/s10096-018-3223-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Acinetobacter baumannii is an opportunistic pathogen associated with nosocomial and community infections of great clinical relevance. Its ability to rapidly develop resistance to antimicrobials, especially carbapenems, has re-boosted the prescription and use of polymyxins. However, the emergence of strains resistant to these antimicrobials is becoming a critical issue in several regions of the world because very few of currently available antibiotics are effective in these cases. This review summarizes the most up-to-date knowledge about chromosomally encoded and plasmid-mediated polymyxins resistance in A. baumannii. Different mechanisms are employed by A. baumannii to overcome the antibacterial effects of polymyxins. Modification of the outer membrane through phosphoethanolamine addition, loss of lipopolysaccharide, symmetric rupture, metabolic changes affecting osmoprotective amino acids, and overexpression of efflux pumps are involved in this process. Several genetic elements modulate these mechanisms, but only three of them have been described so far in A. baumannii clinical isolates such as mutations in pmrCAB, lpxACD, and lpsB. Elucidation of genotypic profiles and resistance mechanisms are necessary for control and fight against resistance to polymyxins in A. baumannii, thereby protecting this class for future treatment.
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Affiliation(s)
- William Gustavo Lima
- Laboratory of Medical Microbiology, Central-West Campus Dona Lindu, Federal University of São João del-Rei, Rua Sebastião Gonçalves Coelho, 400, Divinopolis, Minas Gerais, 35501-293, Brazil.
| | - Mara Cristina Alves
- Laboratory of Laboratorial Diagnostic and Clinical Microbiology, Central-West Campus Dona Lindu, Federal University of São João del-Rei, Divinopolis, MG, Brazil
| | - Waleska Stephanie Cruz
- Laboratory of Molecular and Celular Biology, Alto Paraopeba Campus, Federal University of São João del-Rei, Ouro Branco, MG, Brazil
| | - Magna Cristina Paiva
- Laboratory of Laboratorial Diagnostic and Clinical Microbiology, Central-West Campus Dona Lindu, Federal University of São João del-Rei, Divinopolis, MG, Brazil
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Bakthavatchalam YD, Pragasam AK, Biswas I, Veeraraghavan B. Polymyxin susceptibility testing, interpretative breakpoints and resistance mechanisms: An update. J Glob Antimicrob Resist 2018; 12:124-136. [DOI: 10.1016/j.jgar.2017.09.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/25/2017] [Accepted: 09/19/2017] [Indexed: 12/12/2022] Open
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Farshadzadeh Z, Taheri B, Rahimi S, Shoja S, Pourhajibagher M, Haghighi MA, Bahador A. Growth Rate and Biofilm Formation Ability of Clinical and Laboratory-Evolved Colistin-Resistant Strains of Acinetobacter baumannii. Front Microbiol 2018; 9:153. [PMID: 29483899 PMCID: PMC5816052 DOI: 10.3389/fmicb.2018.00153] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/23/2018] [Indexed: 12/29/2022] Open
Abstract
Two different mechanisms of resistance to colistin in Acinetobacter baumannii have been described. The first involves the total loss of lipopolysaccharide (LPS) due to mutations in the lpxACD operon, which is involved in the lipid A biosynthesis pathway. The second entails the addition of ethanolamine to the lipid A of the LPS resulting from mutations in the PmrAB two-component system. To evaluate the impact of colistin resistance-associated mutations on antimicrobial resistance and virulence properties, four pairs of clinical and laboratory-evolved colistin-susceptible/colistin-resistant (ColS/ColR) A. baumannii isolates were used. Antimicrobial susceptibility, surface motility, in vitro and in vivo biofilm-forming capacity, in vitro and in vivo expression levels of biofilm-associated genes, and in vitro growth rate were analyzed in these strains. Growth rate, in vitro and in vivo biofilm formation ability, as well as expression levels of biofilm-associated gene were reduced in ColR LPS-deficient isolate (the lpxD mutant) when compared with its ColS partner, whereas there were not such differences between LPS-modified isolates (the pmrB mutants) and their parental isolates. Mutation in lpxD was accompanied by a greater reduction in minimum inhibitory concentrations of azithromycin, vancomycin, and rifampin than mutation in pmrB. Besides, loss of LPS was associated with a significant reduction in surface motility without any change in expression of type IV pili. Collectively, colistin resistance through loss of LPS causes a more considerable cost in biological features such as growth rate, motility, and biofilm formation capacity relative to LPS modification. Therefore, ColR LPS-modified strains are more likely to spread and transmit from one patient to another in hospital settings, which results in more complex treatment and control.
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Affiliation(s)
- Zahra Farshadzadeh
- Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Behrouz Taheri
- Department of Medical Laboratory Sciences, School of Paramedicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Sara Rahimi
- Department of Microbiology, Faculty of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
| | - Saeed Shoja
- Infectious and Tropical Disease Research Center, Hormozgan Health Institute, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
| | - Maryam Pourhajibagher
- Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran.,Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad A Haghighi
- Department of Microbiology, Faculty of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
| | - Abbas Bahador
- Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Interplay between Colistin Resistance, Virulence and Fitness in Acinetobacter baumannii. Antibiotics (Basel) 2017; 6:antibiotics6040028. [PMID: 29160808 PMCID: PMC5745471 DOI: 10.3390/antibiotics6040028] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 11/14/2017] [Accepted: 11/20/2017] [Indexed: 12/22/2022] Open
Abstract
Acinetobacter baumannii is an important opportunistic nosocomial pathogen often resistant to multiple antibiotics classes. Colistin, an “old” antibiotic, is now considered a last-line treatment option for extremely resistant isolates. In the meantime, resistance to colistin has been reported in clinical A. baumannii strains. Colistin is a cationic peptide that disrupts the outer membrane (OM) of Gram-negative bacteria. Colistin resistance is primarily due to post-translational modification or loss of the lipopolysaccharide (LPS) molecules inserted into the outer leaflet of the OM. LPS modification prevents the binding of polymyxin to the bacterial surface and may lead to alterations in bacterial virulence. Antimicrobial pressure drives the evolution of antimicrobial resistance and resistance is often associated with a reduced bacterial fitness. Therefore, the alterations in LPS may induce changes in the fitness of A. baumannii. However, compensatory mutations in clinical A. baumannii may ameliorate the cost of resistance and may play an important role in the dissemination of colistin-resistant A. baumannii isolates. The focus of this review is to summarize the colistin resistance mechanisms, and understand their impact on the fitness and virulence of bacteria and on the dissemination of colistin-resistant A. baumannii strains.
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Polymyxins: Antibacterial Activity, Susceptibility Testing, and Resistance Mechanisms Encoded by Plasmids or Chromosomes. Clin Microbiol Rev 2017; 30:557-596. [PMID: 28275006 DOI: 10.1128/cmr.00064-16] [Citation(s) in RCA: 896] [Impact Index Per Article: 128.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Polymyxins are well-established antibiotics that have recently regained significant interest as a consequence of the increasing incidence of infections due to multidrug-resistant Gram-negative bacteria. Colistin and polymyxin B are being seriously reconsidered as last-resort antibiotics in many areas where multidrug resistance is observed in clinical medicine. In parallel, the heavy use of polymyxins in veterinary medicine is currently being reconsidered due to increased reports of polymyxin-resistant bacteria. Susceptibility testing is challenging with polymyxins, and currently available techniques are presented here. Genotypic and phenotypic methods that provide relevant information for diagnostic laboratories are presented. This review also presents recent works in relation to recently identified mechanisms of polymyxin resistance, including chromosomally encoded resistance traits as well as the recently identified plasmid-encoded polymyxin resistance determinant MCR-1. Epidemiological features summarizing the current knowledge in that field are presented.
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Transcriptional and Mutational Profiling of an Aminoglycoside-Resistant Pseudomonas aeruginosa Small-Colony Variant. Antimicrob Agents Chemother 2017; 61:AAC.01178-17. [PMID: 28874369 DOI: 10.1128/aac.01178-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/18/2017] [Indexed: 02/01/2023] Open
Abstract
Pseudomonas aeruginosa is a major causative agent of both acute and chronic infections. Although aminoglycoside antibiotics are very potent drugs against such infections, antibiotic failure is steadily increasing mainly because of increasing resistance of the bacteria. Many molecular mechanisms that determine resistance, such as acquisition of genes encoding aminoglycoside-inactivating enzymes or overexpression of efflux pumps, have been elucidated. However, there are additional, less well-described mechanisms of aminoglycoside resistance. In this study, we profiled a clinical tobramycin-resistant P. aeruginosa strain that exhibited a small-colony variant (SCV) phenotype. Both the resistance and colony morphology phenotypes were lost upon passage of the isolate under rich medium conditions. Transcriptional and mutational profiling revealed that the SCV harbored activating mutations in the two-component systems AmgRS and PmrAB. Introduction of these mutations individually into type strain PA14 conferred tobramycin and colistin resistance, respectively. However, their combined introduction had an additive effect on the tobramycin resistance phenotype. Activation of the AmgRS system slightly reduced the colony size of wild-type PA14, whereas the simultaneous overexpression of gacA, the response regulator of the GacSA two-component system, further reduced colony size. In conclusion, we uncovered combinatorial influences of two-component systems on clinically relevant phenotypes such as resistance and the expression of the SCV phenotype. Our results clearly demonstrate that the combined activation of P. aeruginosa two-component systems has pleiotropic effects with unforeseen consequences.
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41
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Rabanal F, Cajal Y. Recent advances and perspectives in the design and development of polymyxins. Nat Prod Rep 2017. [PMID: 28628170 DOI: 10.1039/c7np00023e] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Covering: 1947-early 2017, particularly from 2005-early 2017The rise of bacterial pathogens with acquired resistance to almost all available antibiotics is becoming a serious public health issue. Polymyxins, antibiotics that were mostly abandoned a few decades ago because of toxicity concerns, are ultimately considered as a last-line therapy to treat infections caused by multi-drug resistant Gram-negative bacteria. This review surveys the progress in understanding polymyxin structure, and their chemistry, mechanisms of antibacterial activity and nephrotoxicity, biomarkers, synergy and combination with other antimicrobial agents and antibiofilm properties. An update of recent efforts in the design and development of a new generation of polymyxin drugs is also discussed. A novel approach considering the modification of the scaffold of polymyxins to integrate metabolism and detoxification issues into the drug design process is a promising new line to potentially prevent accumulation in the kidneys and reduce nephrotoxicity.
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Affiliation(s)
- Francesc Rabanal
- Organic Chemistry Section, Department of Inorganic and Organic Chemistry, Faculty of Chemistry, University of Barcelona, Spain.
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42
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Wand ME, Bock LJ, Sutton JM. Retention of virulence following colistin adaptation in Klebsiella pneumoniae is strain-dependent rather than associated with specific mutations. J Med Microbiol 2017; 66:959-964. [PMID: 28741998 DOI: 10.1099/jmm.0.000530] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
This study aimed to understand the impact on virulence and fitness of mutations in specific genes found after adaptation of Klebsiella pneumoniae to colistin. Isolates with an increase in their inhibitory concentration (MIC) to colistin of 32- to >128-fold were shown to have mutations in mgrB, phoPQ and pmrAB, all known regulators of pathways affecting membrane lipid content. When these strains were used in studies in Galleria mellonella there was no clear correlation between mutations in specific genes per se and loss of virulence. Strains which showed sequence duplication in the HAMP-domain of PmrB showed reduced virulence but strains with point mutations in pmrAB showed no decrease in virulence. Similarly, specific mutations in mgrB in individual strains showed either loss of virulence or no effect/increased virulence. This study suggests that the impact on virulence may be independent of the colistin resistance mechanism and reflects differences in individual strain backgrounds.
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Affiliation(s)
- Matthew E Wand
- Public Health England, National Infection Service, Porton Down, Salisbury, Wiltshire, SP4 0JG, UK
| | - Lucy J Bock
- Public Health England, National Infection Service, Porton Down, Salisbury, Wiltshire, SP4 0JG, UK
| | - J Mark Sutton
- Public Health England, National Infection Service, Porton Down, Salisbury, Wiltshire, SP4 0JG, UK
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Dahdouh E, Gómez-Gil R, Sanz S, González-Zorn B, Daoud Z, Mingorance J, Suárez M. A novel mutation in pmrB mediates colistin resistance during therapy of Acinetobacter baumannii. Int J Antimicrob Agents 2017; 49:727-733. [PMID: 28438568 DOI: 10.1016/j.ijantimicag.2017.01.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/20/2017] [Accepted: 01/28/2017] [Indexed: 11/29/2022]
Abstract
Acinetobacter baumannii is a highly versatile nosocomial pathogen. Multidrug resistance among A. baumannii isolates led to the use of colistin, subsequently giving rise to colistin-resistant strains. In this study, the genetic and phenotypic profiles of two colistin-resistant A. baumannii isolates were investigated. Two A. baumannii isolates were obtained from Patient 1 (C071 and C440) and three isolates were obtained from Patient 2 (C080, C314 and C428). Susceptibility profiles were determined by VITEK®2 and Etest. Clonality was determined by RAPD analysis and trilocus multiplex PCR. The pmrCAB operon was sequenced and common carbapenemase genes were screened for by PCR. Doubling times, haemolysis, surface motility, biofilm formation, siderophore production and proteolytic activity were phenotypically determined. Finally, whole-genome sequencing was performed for all five isolates. Isolates C440 and C428 were resistant to colistin and were clonally identical to their sensitive counterparts. The cause of colistin resistance was traced to the previously described P233S mutation in pmrB of C440 and to a novel ΔI19 mutation in pmrB of C428. blaOXA-58-like and blaGES-5 from the strains of Patients 1 and 2, respectively, were also detected. C440 had attenuated proteolytic activity and was positive for siderophore production compared with C071. No difference in in vitro virulence was detected between isolates C080, C314 and C428. In conclusion, one common and one novel mutation were encountered in pmrB from two distinct colistin-resistant A. baumannii isolates. These mutations caused colistin resistance during therapy in two distinct clones, and only one of them had altered in vitro virulence.
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Affiliation(s)
- Elias Dahdouh
- Faculty of Veterinary, Department of Animal Health, Universidad Complutense de Madrid, Laboratory 206, Puerta de Hierro s/n, 28040 Madrid, Spain.
| | - Rosa Gómez-Gil
- Servicio de Microbiología, Hospital Universitario La Paz, IdiPAZ, Madrid, Spain
| | - Sonia Sanz
- Servicio de Microbiología, Hospital Universitario La Paz, IdiPAZ, Madrid, Spain
| | - Bruno González-Zorn
- Faculty of Veterinary, Department of Animal Health, Universidad Complutense de Madrid, Laboratory 206, Puerta de Hierro s/n, 28040 Madrid, Spain
| | - Ziad Daoud
- Faculty of Medicine, Department of Clinical Microbiology, University of Balamand, Balamand, Lebanon
| | - Jesús Mingorance
- Servicio de Microbiología, Hospital Universitario La Paz, IdiPAZ, Madrid, Spain
| | - Monica Suárez
- Faculty of Veterinary, Department of Animal Health, Universidad Complutense de Madrid, Laboratory 206, Puerta de Hierro s/n, 28040 Madrid, Spain
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Rhouma M, Beaudry F, Thériault W, Letellier A. Colistin in Pig Production: Chemistry, Mechanism of Antibacterial Action, Microbial Resistance Emergence, and One Health Perspectives. Front Microbiol 2016; 7:1789. [PMID: 27891118 PMCID: PMC5104958 DOI: 10.3389/fmicb.2016.01789] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/25/2016] [Indexed: 01/08/2023] Open
Abstract
Colistin (Polymyxin E) is one of the few cationic antimicrobial peptides commercialized in both human and veterinary medicine. For several years now, colistin has been considered the last line of defense against infections caused by multidrug-resistant Gram-negative such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Colistin has been extensively used orally since the 1960s in food animals and particularly in swine for the control of Enterobacteriaceae infections. However, with the recent discovery of plasmid-mediated colistin resistance encoded by the mcr-1 gene and the higher prevalence of samples harboring this gene in animal isolates compared to other origins, livestock has been singled out as the principal reservoir for colistin resistance amplification and spread. Co-localization of the mcr-1 gene and Extended-Spectrum-β-Lactamase genes on a unique plasmid has been also identified in many isolates from animal origin. The use of colistin in pigs as a growth promoter and for prophylaxis purposes should be banned, and the implantation of sustainable measures in pig farms for microbial infection prevention should be actively encouraged and financed. The scientific research should be encouraged in swine medicine to generate data helping to reduce the exacerbation of colistin resistance in pigs and in manure. The establishment of guidelines ensuring a judicious therapeutic use of colistin in pigs, in countries where this drug is approved, is of crucial importance. The implementation of a microbiological withdrawal period that could reduce the potential contamination of consumers with colistin resistant bacteria of porcine origin should be encouraged. Moreover, the management of colistin resistance at the human-pig-environment interface requires the urgent use of the One Health approach for effective control and prevention. This approach needs the collaborative effort of multiple disciplines and close cooperation between physicians, veterinarians, and other scientific health and environmental professionals. This review is an update on the chemistry of colistin, its applications and antibacterial mechanism of action, and on Enterobacteriaceae resistance to colistin in pigs. We also detail and discuss the One Health approach and propose guidelines for colistin resistance management.
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Affiliation(s)
- Mohamed Rhouma
- Chaire de Recherche Industrielle du CRSNG en Salubrité des Viandes, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Groupe de Recherche et d’Enseignement en Salubrité Alimentaire, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
| | - Francis Beaudry
- Centre de Recherche en Infectiologie Porcine et Avicole, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Groupe de Recherche en Pharmacologie Animale du Québec, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
| | - William Thériault
- Chaire de Recherche Industrielle du CRSNG en Salubrité des Viandes, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Groupe de Recherche et d’Enseignement en Salubrité Alimentaire, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
| | - Ann Letellier
- Chaire de Recherche Industrielle du CRSNG en Salubrité des Viandes, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Groupe de Recherche et d’Enseignement en Salubrité Alimentaire, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
- Groupe de Recherche en Pharmacologie Animale du Québec, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-HyacintheQC, Canada
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Trimble MJ, Mlynárčik P, Kolář M, Hancock REW. Polymyxin: Alternative Mechanisms of Action and Resistance. Cold Spring Harb Perspect Med 2016; 6:cshperspect.a025288. [PMID: 27503996 DOI: 10.1101/cshperspect.a025288] [Citation(s) in RCA: 243] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Antibiotic resistance among pathogenic bacteria is an ever-increasing issue worldwide. Unfortunately, very little has been achieved in the pharmaceutical industry to combat this problem. This has led researchers and the medical field to revisit past drugs that were deemed too toxic for clinical use. In particular, the cyclic cationic peptides polymyxin B and colistin, which are specific for Gram-negative bacteria, have been used as "last resort" antimicrobials. Before the 1980s, these drugs were known for their renal and neural toxicities; however, new clinical practices and possibly improved manufacturing have made them safer to use. Previously suggested to primarily attack the membranes of Gram-negative bacteria and to not easily select for resistant mutants, recent research exploring resistance and mechanisms of action has provided new perspectives. This review focuses primarily on the proposed alternative mechanisms of action, known resistance mechanisms, and how these support the alternative mechanisms of action.
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Affiliation(s)
- Michael J Trimble
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Patrik Mlynárčik
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Milan Kolář
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Robert E W Hancock
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Synergy between Colistin and the Signal Peptidase Inhibitor MD3 Is Dependent on the Mechanism of Colistin Resistance in Acinetobacter baumannii. Antimicrob Agents Chemother 2016; 60:4375-9. [PMID: 27139471 DOI: 10.1128/aac.00510-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 04/24/2016] [Indexed: 02/08/2023] Open
Abstract
Synergy between colistin and the signal peptidase inhibitor MD3 was tested against isogenic mutants and clinical pairs of Acinetobacter baumannii isolates. Checkerboard assays and growth curves showed synergy against both colistin-susceptible strains (fractional inhibitory concentration index [FICindex] = 0.13 to 0.24) and colistin-resistant strains with mutations in pmrB and phosphoethanolamine modification of lipid A (FICindex = 0.14 to 0.25) but not against colistin-resistant Δlpx strains with loss of lipopolysaccharide (FICindex = 0.75 to 1). A colistin/MD3 combination would need to be targeted to strains with specific colistin resistance mechanisms.
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Tseng CC, Tsai YH, Hu A, Liou JW, Chang KC, Chang HH. Altered susceptibility to the bactericidal effect of photocatalytic oxidation by TiO2 is related to colistin resistance development in Acinetobacter baumannii. Appl Microbiol Biotechnol 2016; 100:8549-61. [DOI: 10.1007/s00253-016-7654-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/24/2016] [Accepted: 05/27/2016] [Indexed: 10/21/2022]
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48
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López-Rojas R, García-Quintanilla M, Labrador-Herrera G, Pachón J, McConnell MJ. Impaired growth under iron-limiting conditions associated with the acquisition of colistin resistance in Acinetobacter baumannii. Int J Antimicrob Agents 2016; 47:473-7. [PMID: 27179817 DOI: 10.1016/j.ijantimicag.2016.03.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 03/14/2016] [Accepted: 03/19/2016] [Indexed: 11/19/2022]
Abstract
Acquisition of colistin resistance in Acinetobacter baumannii has been associated with reduced bacterial fitness and virulence, although the mechanisms underlying this fitness loss have not been well characterised. In this study, the role played by environmental iron levels on the growth and survival of colistin-resistant strains of A. baumannii was assessed. Growth assays with the colistin-susceptible ATCC 19606 strain and its colistin-resistant derivative RC64 [colistin minimum inhibitory concentration (MIC) of 64 mg/L] demonstrated that the strains grew similarly in rich laboratory medium (Mueller-Hinton broth), whereas RC64 demonstrated impaired growth compared with ATCC 19606 in human serum (>100-fold at 24 h). Compared with RC64, ATCC 19606 grew in the presence of higher concentrations of the iron-specific chelator 2,2'-bipyridine and grew more readily under iron-limiting conditions in solid and liquid media. In addition, iron supplementation of human serum increased the growth of RC64 compared with unsupplemented human serum to a greater extent than ATCC 19606. The ability of 11 colistin-resistant clinical isolates with mutations in the pmrB gene to grow in iron-replete and iron-limiting conditions was assessed, demonstrating that eight of the strains showed reduced growth under iron limitation. Individual mutations in the pmrB gene did not directly correlate with a decreased capacity for growth under iron limitation, suggesting that mutations in pmrB may not directly produce this phenotype. Together these results indicate that acquisition of colistin resistance in A. baumannii can be associated with a decreased ability to grow in low-iron environments.
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Affiliation(s)
- Rafael López-Rojas
- Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville 41013, Spain
| | - Meritxell García-Quintanilla
- Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville 41013, Spain
| | - Gema Labrador-Herrera
- Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville 41013, Spain
| | - Jerónimo Pachón
- Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville 41013, Spain
| | - Michael J McConnell
- Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville 41013, Spain.
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50
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Pérez-Llarena FJ, Bou G. Proteomics As a Tool for Studying Bacterial Virulence and Antimicrobial Resistance. Front Microbiol 2016; 7:410. [PMID: 27065974 PMCID: PMC4814472 DOI: 10.3389/fmicb.2016.00410] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 03/14/2016] [Indexed: 12/31/2022] Open
Abstract
Proteomic studies have improved our understanding of the microbial world. The most recent advances in this field have helped us to explore aspects beyond genomics. For example, by studying proteins and their regulation, researchers now understand how some pathogenic bacteria have adapted to the lethal actions of antibiotics. Proteomics has also advanced our knowledge of mechanisms of bacterial virulence and some important aspects of how bacteria interact with human cells and, thus, of the pathogenesis of infectious diseases. This review article addresses these issues in some of the most important human pathogens. It also reports some applications of Matrix-Assisted Laser Desorption/Ionization-Time-Of-Flight (MALDI-TOF) mass spectrometry that may be important for the diagnosis of bacterial resistance in clinical laboratories in the future. The reported advances will enable new diagnostic and therapeutic strategies to be developed in the fight against some of the most lethal bacteria affecting humans.
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Affiliation(s)
| | - Germán Bou
- Servicio de Microbiología-INIBIC, Complejo Hospitalario Universitario A Coruña A Coruña, Spain
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