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Raddaoui A, Mabrouk A, Chebbi Y, Frigui S, Salah Abbassi M, Achour W, Thabet L. Co-occurrence of blaNDM-1 and blaOXA-23 in carbapenemase-producing Acinetobacter baumannii belonging to high-risk lineages isolated from burn patients in Tunisia. J Appl Microbiol 2024; 135:lxae039. [PMID: 38346864 DOI: 10.1093/jambio/lxae039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 01/10/2024] [Accepted: 02/09/2024] [Indexed: 03/21/2024]
Abstract
AIMS Carbapenem-resistant Acinetobacter baumannii (CR-Ab) is an important cause of infections in burn patients. This study aimed to characterize the antimicrobial susceptibility pattern of CR-Ab isolated from burns in Burn Intensive Care Unit (BICU) of the Trauma and Burn Centre of Ben Arous, to determine the prevalence of β-lactamase-encoding genes and to search eventual genetic relatedness of CR-Ab strains. METHODS AND RESULTS From 15 December 2016 to 2 April 2017, all nonduplicated CR-Ab isolated in burn patients in the BICU were screened by simplex Polymerase Chain Reaction (PCR) for the class A, B, C, and D β-lactamase genes. Sequencing was performed for NDM gene only. Genetic relatedness was determined by using pulsed field gel electrophoresis (PFGE) and by multilocus sequence typing. During the study period, 34 strains of CR-Ab were isolated in burns, mainly in blood culture (n = 14) and central vascular catheter (n = 10). CR-Ab strains were susceptible to colistin but resistant to amikacin (91%), ciprofloxacin (100%), rifampicin (97%), and trimethoprim-sulfamethoxazole (100%). All strains harbored blaOXA-51-like and blaOXA-23 genes, only or associated to blaGES (n = 26; 76%), blaADC (n = 20; 59%), blaPER-1 (n = 6; 18%) or/and blaNDM-1 (n = 3; 9%). PFGE identified 16 different clusters and revealed that most strains belonged to one major cluster A (n = 15; 44.1%). Among NDM-1 isolates, two were clonally related in PFGE and belonged to two single locus variant sequence type ST-6 and ST-85. CONCLUSIONS This is the first description of clonally related NDM-1 and OXA-23-producing A. baumannii strains in the largest Tunisian BICU associated with two single locus variant sequence types ST6 and ST85.
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Affiliation(s)
- Anis Raddaoui
- Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia
- Faculty of Medicine of Tunis, LR18ES39, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Aymen Mabrouk
- Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia
- Faculty of Medicine of Tunis, LR18ES39, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Yosra Chebbi
- Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia
- Faculty of Medicine of Tunis, LR18ES39, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Siwar Frigui
- Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia
- Faculty of Medicine of Tunis, LR18ES39, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Mohamed Salah Abbassi
- Faculty of Medicine of Tunis, Laboratory of Antibiotic Resistance LR99ES09, University of Tunis El Manar, 1006 Tunis, Tunisia
- Institute of Veterinary Research of Tunisia, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Wafa Achour
- Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia
- Faculty of Medicine of Tunis, LR18ES39, University of Tunis El Manar, 1006 Tunis, Tunisia
| | - Lamia Thabet
- Laboratory Ward, Traumatology and Great Burned Center, 2074 Ben Arous, Tunisia
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Azaiez S, Haenni M, Cheikh AB, Chalbi MS, Messaoudi A, Tilouch L, Bahri S, Drapeau A, Saras E, Mtibâa M, Zouaoui R, Said H, Madec JY, Lupo A, Mansour W. Healthcare Equipment and Personnel Reservoirs of Carbapenem-Resistant Acinetobacter baumannii Epidemic Clones in Intensive Care Units in a Tunisian Hospital. Microorganisms 2023; 11:2637. [PMID: 38004649 PMCID: PMC10672855 DOI: 10.3390/microorganisms11112637] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/18/2023] [Accepted: 10/19/2023] [Indexed: 11/26/2023] Open
Abstract
Carbapenem-resistant Acinetobacter baumannii (CRAB) strains can cause severe and difficult-to-treat infections in patients with compromised general health. CRAB strains disseminate rapidly in nosocomial settings by patient-to-patient contact, through medical devices and inanimate reservoirs. The occurrence of CRAB in patients residing in the intensive care units (ICUs) of the Sahloul University hospital in Sousse, Tunisia is high. The objective of the current study was to determine whether the surfaces of items present in five ICU wards and the medical personnel there operating could serve as reservoirs for CRAB strains. Furthermore, CRAB isolates from patients residing in the ICUs during the sampling campaign were analyzed for genome comparison with isolates from the ICUs environment. Overall, 206 items were screened for CRAB presence and 27 (14%) were contaminated with a CRAB isolate. The items were located in several areas of three ICUs. Eight of the 54 (15%) screened people working in the wards were colonized by CRAB on the hands. Patients residing in the ICUs were infected with CRAB strains sharing extensive genomic similarity with strains recovered in the nosocomial environment. The strains belonged to three sub-clades of the internationally disseminated clone (ST2). A clone emerging in the Mediterranean basin (ST85) was detected as well. The strains were OXA-23 or NDM-1 producers and were also pan-aminoglycoside resistant due to the presence of the armA gene. Hygiene measures are urgent to be implemented in the Sahloul hospital to avoid further spread of difficult-to-treat CRAB strains and preserve health of patients and personnel operating in the ICU wards.
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Affiliation(s)
- Sana Azaiez
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
| | - Marisa Haenni
- Unité Antibiorésistance et Virulence Bactériennes, ANSES—Université de Lyon, 69007 Lyon, France; (M.H.); (A.D.); (E.S.); (J.-Y.M.)
| | - Asma Ben Cheikh
- Departement of Prevention and Security of Care, Sahloul University Hospital of Sousse, Sousse 4054, Tunisia; (A.B.C.); (M.S.C.); (H.S.)
- Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia
| | - Mohamed Sahbi Chalbi
- Departement of Prevention and Security of Care, Sahloul University Hospital of Sousse, Sousse 4054, Tunisia; (A.B.C.); (M.S.C.); (H.S.)
- Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia
| | - Aziza Messaoudi
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
| | - Lamia Tilouch
- Laboratoire de Microbiologie Sahloul, University Hospital of Sousse, Sousse 4054, Tunisia;
- Faculté de Pharmacie, Université de Monastir, Monastir 5019, Tunisia
| | - Sana Bahri
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
| | - Antoine Drapeau
- Unité Antibiorésistance et Virulence Bactériennes, ANSES—Université de Lyon, 69007 Lyon, France; (M.H.); (A.D.); (E.S.); (J.-Y.M.)
| | - Estelle Saras
- Unité Antibiorésistance et Virulence Bactériennes, ANSES—Université de Lyon, 69007 Lyon, France; (M.H.); (A.D.); (E.S.); (J.-Y.M.)
| | - Mariem Mtibâa
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
| | - Rania Zouaoui
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
| | - Houyem Said
- Departement of Prevention and Security of Care, Sahloul University Hospital of Sousse, Sousse 4054, Tunisia; (A.B.C.); (M.S.C.); (H.S.)
- Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia
| | - Jean-Yves Madec
- Unité Antibiorésistance et Virulence Bactériennes, ANSES—Université de Lyon, 69007 Lyon, France; (M.H.); (A.D.); (E.S.); (J.-Y.M.)
| | - Agnese Lupo
- Unité Antibiorésistance et Virulence Bactériennes, ANSES—Université de Lyon, 69007 Lyon, France; (M.H.); (A.D.); (E.S.); (J.-Y.M.)
| | - Wejdene Mansour
- Laboratoire de Recherche Biophysique Métabolique et Pharmacologie Appliquée, LR12ES02, Faculté de Médecine Ibn Al Jazzar Sousse, Université de Sousse, Sousse 4002, Tunisia; (S.A.); (A.M.); (S.B.); (M.M.); (R.Z.)
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Junaid M, Thirapanmethee K, Khuntayaporn P, Chomnawang MT. CRISPR-Based Gene Editing in Acinetobacter baumannii to Combat Antimicrobial Resistance. Pharmaceuticals (Basel) 2023; 16:920. [PMID: 37513832 PMCID: PMC10384873 DOI: 10.3390/ph16070920] [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: 05/25/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 07/30/2023] Open
Abstract
Antimicrobial resistance (AMR) poses a significant threat to the health, social, environment, and economic sectors on a global scale and requires serious attention to addressing this issue. Acinetobacter baumannii was given top priority among infectious bacteria because of its extensive resistance to nearly all antibiotic classes and treatment options. Carbapenem-resistant A. baumannii is classified as one of the critical-priority pathogens on the World Health Organization (WHO) priority list of antibiotic-resistant bacteria for effective drug development. Although available genetic manipulation approaches are successful in A. baumannii laboratory strains, they are limited when employed on newly acquired clinical strains since such strains have higher levels of AMR than those used to select them for genetic manipulation. Recently, the CRISPR-Cas (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) system has emerged as one of the most effective, efficient, and precise methods of genome editing and offers target-specific gene editing of AMR genes in a specific bacterial strain. CRISPR-based genome editing has been successfully applied in various bacterial strains to combat AMR; however, this strategy has not yet been extensively explored in A. baumannii. This review provides detailed insight into the progress, current scenario, and future potential of CRISPR-Cas usage for AMR-related gene manipulation in A. baumannii.
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Affiliation(s)
- Muhammad Junaid
- Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
- Antimicrobial Resistance Interdisciplinary Group (AmRIG), Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
| | - Krit Thirapanmethee
- Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
- Antimicrobial Resistance Interdisciplinary Group (AmRIG), Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
| | - Piyatip Khuntayaporn
- Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
- Antimicrobial Resistance Interdisciplinary Group (AmRIG), Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
| | - Mullika Traidej Chomnawang
- Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
- Antimicrobial Resistance Interdisciplinary Group (AmRIG), Faculty of Pharmacy, Mahidol University, Bangkok 10400, Thailand
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Ferjani S, Kanzari L, Maamar E, Hamzaoui Z, Rehaiem A, Ferjani A, Boutiba-Ben Boubaker I. Extensively drug-resistant Acinetobacter baumannii co-producing VIM-2 and OXA-23 in intensive care units: Results of a one-day point prevalence in a Tunisian hospital. Infect Dis Now 2022; 52:426-431. [DOI: 10.1016/j.idnow.2022.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/05/2022] [Accepted: 09/05/2022] [Indexed: 11/26/2022]
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Abouelfetouh A, Mattock J, Turner D, Li E, Evans BA. Diversity of carbapenem-resistant Acinetobacter baumannii and bacteriophage-mediated spread of the Oxa23 carbapenemase. Microb Genom 2022; 8. [PMID: 35104206 PMCID: PMC8942029 DOI: 10.1099/mgen.0.000752] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Carbapenem-resistant Acinetobacter baumannii are prevalent in low- and middle-income countries such as Egypt, but little is known about the molecular epidemiology and mechanisms of resistance in these settings. Here, we characterize carbapenem-resistant A. baumannii from Alexandria, Egypt, and place it in a regional context. Fifty-four carbapenem-resistant isolates from Alexandria Main University Hospital (AMUH), Alexandria, Egypt, collected between 2010 and 2015 were genome sequenced using Illumina technology. Genomes were de novo assembled and annotated. Genomes for 36 isolates from the Middle East region were downloaded from GenBank. The core-gene compliment was determined using Roary, and analyses of recombination were performed in Gubbins. Multilocus sequence typing (MLST) sequence type (ST) and antibiotic-resistance genes were identified. The majority of Egyptian isolates belonged to one of three major clades, corresponding to Pasteur MLST clonal complex (CCPAS) 1, CCPAS2 and STPAS158. Strains belonging to STPAS158 have been reported almost exclusively from North Africa, the Middle East and Pakistan, and may represent a region-specific lineage. All isolates carried an oxa23 gene, six carried bla NDM-1 and one carried bla NDM-2. The oxa23 gene was located on a variety of different mobile elements, with Tn2006 predominant in CCPAS2 strains, and Tn2008 predominant in other lineages. Of particular concern, in 8 of the 13 CCPAS1 strains, the oxa23 gene was located in a temperate bacteriophage phiOXA, previously identified only once before in a CCPAS1 clone from the USA military. The carbapenem-resistant A. baumannii population in AMUH is very diverse, and indicates an endemic circulating population, including a region-specific lineage. A major mechanism for oxa23 dissemination in CCPAS1 isolates appears to be a bacteriophage, presenting new concerns about the ability of these carbapenemases to spread throughout the bacterial population.
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Affiliation(s)
- Alaa Abouelfetouh
- Department of Microbiology and Immunology, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt
| | | | - Dann Turner
- Department of Applied Sciences, University of the West of England, Bristol, UK
| | - Erica Li
- Norwich Medical School, University of East Anglia, Norwich, UK
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Ragheb SM, Govinden U, Osei Sekyere J. Genetic support of carbapenemases: a One Health systematic review and meta-analysis of current trends in Africa. Ann N Y Acad Sci 2021; 1509:50-73. [PMID: 34753206 DOI: 10.1111/nyas.14703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 09/06/2021] [Accepted: 09/26/2021] [Indexed: 11/28/2022]
Abstract
Antimicrobial resistance (AMR) is a public health threat globally. Carbapenems are β-lactam antibiotics used as last-resort agents for treating antibiotic-resistant infections. Mobile genetic elements (MGEs) play an important role in the dissemination and expression of antimicrobial resistance genes (ARGs), including the mobilization of ARGs within and between species. The presence of MGEs around carbapenem-hydrolyzing enzymes, called carbapenemases, in bacterial isolates in Africa is concerning. The association between MGEs and carbapenemases is described herein. Specific plasmid replicons, integrons, transposons, and insertion sequences were found flanking specific and different carbapenemases across the same and different clones and species isolated from humans, animals, and the environment. Notably, similar genetic contexts have been reported in non-African countries, supporting the importance of MGEs in driving the intra- and interclonal and species transmission of carbapenemases in Africa and globally. Technical and budgetary limitations remain challenges for epidemiological analysis of carbapenemases in Africa, as studies undertaken with whole-genome sequencing remained relatively few. Characterization of MGEs in antibiotic-resistant infections can deepen our understanding of carbapenemase epidemiology and facilitate the control of AMR in Africa. Investment in genomic epidemiology will facilitate faster clinical interventions and containment of outbreaks.
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Affiliation(s)
- Suzan Mohammed Ragheb
- Department of Microbiology and Immunology, Faculty of Pharmacy, Modern University for Technology and Information (MTI), Cairo, Egypt
| | - Usha Govinden
- Discipline of Pharmaceutical Sciences, College of Health Sciences, University of KwaZulu-Natal, KwaZulu-Natal, South Africa
| | - John Osei Sekyere
- Department of Microbiology & Immunology, Indiana University School of Medicine-Northwest, Gary, Indiana.,Department of Dermatology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
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Mabrouk A, Chebbi Y, Raddaoui A, Krir A, Messadi AA, Achour W, Thabet L. Clonal spread of PER-1 and OXA-23 producing extensively drug resistant Acinetobacter baumannii during an outbreak in a burn intensive care unit in Tunisia. Acta Microbiol Immunol Hung 2020; 67:222-227. [PMID: 33216011 DOI: 10.1556/030.2020.01208] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 08/10/2020] [Indexed: 11/19/2022]
Abstract
Extensively drug resistant Acinetobacter baumannii (XDR-Ab), has emerged as an important pathogen in several outbreaks. The aim of our study was to investigate the eventual genetic relatedness of XDR-Ab strains recovered from burn patients and environment sites in the largest Tunisian Burn Intensive Care Unit (BICU) and to characterize β-lactamase encoding genes in these strains. Between March 04th, 2019 and April 22nd, 2019 an outbreak of XDR-Ab was suspected. Environmental screening was done. All isolates were screened by simplex PCR for β-lactamase genes. Genetic relatedness was determined by pulsed field gel electrophoresis (PFGE) of ApaI-digested total DNA. During the study period, 21 strains of A. baumannii were isolated in burn patients, mainly in blood culture (n = 7) and central vascular catheter (n = 6). All strains were susceptible to colistin but resistant to imipenem (n = 23), ciprofloxacin (n = 23), amikacin (n = 22), tigecyclin (n = 5) and rifampicin (n = 4). The blaOXA-51-like, blaOXA23, and blaADC genes were present in all strains. These resistance determinants were associated with blaPER-1 in 10 strains. The ISAba1 was inserted upstream of blaOXA-23 in all isolates. PFGE revealed two major clusters A (n = 11) and B (n = 5). This is the first description in Tunisia of clonally related PER-1 producing XDR-Ab in burn patients with probable environmental origin.
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Affiliation(s)
- Aymen Mabrouk
- 1Laboratory Ward, National Bone Marrow Transplant Center, 1006, Tunis, Tunisia
- 2Tunis El Manar University, Faculty of Medicine of Tunis, LR18ES39, 1006, Tunis, Tunisia
| | - Yosra Chebbi
- 1Laboratory Ward, National Bone Marrow Transplant Center, 1006, Tunis, Tunisia
- 2Tunis El Manar University, Faculty of Medicine of Tunis, LR18ES39, 1006, Tunis, Tunisia
| | - Anis Raddaoui
- 1Laboratory Ward, National Bone Marrow Transplant Center, 1006, Tunis, Tunisia
- 2Tunis El Manar University, Faculty of Medicine of Tunis, LR18ES39, 1006, Tunis, Tunisia
| | - Asma Krir
- 4Burns Intensive Care Unit, Traumatology and Great Burned Center, 2074, Ben Arous, Tunisia
| | - Amen Allah Messadi
- 4Burns Intensive Care Unit, Traumatology and Great Burned Center, 2074, Ben Arous, Tunisia
| | - Wafa Achour
- 1Laboratory Ward, National Bone Marrow Transplant Center, 1006, Tunis, Tunisia
- 2Tunis El Manar University, Faculty of Medicine of Tunis, LR18ES39, 1006, Tunis, Tunisia
| | - Lamia Thabet
- 2Tunis El Manar University, Faculty of Medicine of Tunis, LR18ES39, 1006, Tunis, Tunisia
- 3Laboratory Ward, Traumatology and Great Burned Center, 2074, Ben Arous, Tunisia
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Copy Number of an Integron-Encoded Antibiotic Resistance Locus Regulates a Virulence and Opacity Switch in Acinetobacter baumannii AB5075. mBio 2020; 11:mBio.02338-20. [PMID: 33024041 PMCID: PMC7542366 DOI: 10.1128/mbio.02338-20] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acinetobacter baumannii remains a leading cause of hospital-acquired infections. Widespread multidrug resistance in this species has prompted the WHO to name carbapenem-resistant A. baumannii as its top priority for research and development of new antibiotics. Many strains of A. baumannii undergo a high-frequency virulence switch, which is an attractive target for new therapeutics targeting this pathogen. This study reports a novel mechanism controlling the frequency of switching in strain AB5075. The rate of switching from the virulent opaque (VIR-O) to the avirulent translucent (AV-T) variant is positively influenced by the copy number of an antibiotic resistance locus encoded on a plasmid-borne composite integron. Our data suggest that this locus encodes a small RNA that regulates opacity switching. Low-switching opaque variants, which harbor a single copy of this locus, also exhibit decreased virulence. This study increases our understanding of this critical phenotypic switch, while also identifying potential targets for virulence-based A. baumannii treatments. We describe a novel genetic mechanism in which tandem amplification of a plasmid-borne integron regulates virulence, opacity variation, and global gene expression by altering levels of a putative small RNA (sRNA) in Acinetobacter baumannii AB5075. Copy number of this amplified locus correlated with the rate of switching between virulent opaque (VIR-O) and avirulent translucent (AV-T) cells. We found that prototypical VIR-O colonies, which exhibit high levels of switching and visible sectoring with AV-T cells by 24 h of growth, harbor two copies of this locus. However, a subset of opaque colonies that did not form AV-T sectors within 24 h were found to harbor only one copy. The colonies with decreased sectoring to AV-T were designated low-switching opaque (LSO) variants and were found to exhibit a 3-log decrease in switching relative to that of the VIR-O. Overexpression studies revealed that the element regulating switching was localized to the 5′ end of the aadB gene within the amplified locus. Northern blotting indicated that an sRNA of approximately 300 nucleotides (nt) is encoded in this region and is likely responsible for regulating switching to AV-T. Copy number of the ∼300-nt sRNA was also found to affect virulence, as the LSO variant exhibited decreased virulence during murine lung infections. Global transcriptional profiling revealed that >100 genes were differentially expressed between VIR-O and LSO variants, suggesting that the ∼300-nt sRNA may act as a global regulator. Several virulence genes exhibited decreased expression in LSO cells, potentially explaining their decreased virulence.
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Antibiotic Resistance Profiles, Molecular Mechanisms and Innovative Treatment Strategies of Acinetobacter baumannii. Microorganisms 2020; 8:microorganisms8060935. [PMID: 32575913 PMCID: PMC7355832 DOI: 10.3390/microorganisms8060935] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/19/2020] [Accepted: 06/19/2020] [Indexed: 12/18/2022] Open
Abstract
Antibiotic resistance is one of the biggest challenges for the clinical sector and industry, environment and societal development. One of the most important pathogens responsible for severe nosocomial infections is Acinetobacter baumannii, a Gram-negative bacterium from the Moraxellaceae family, due to its various resistance mechanisms, such as the β-lactamases production, efflux pumps, decreased membrane permeability and altered target site of the antibiotic. The enormous adaptive capacity of A. baumannii and the acquisition and transfer of antibiotic resistance determinants contribute to the ineffectiveness of most current therapeutic strategies, including last-line or combined antibiotic therapy. In this review, we will present an update of the antibiotic resistance profiles and underlying mechanisms in A. baumannii and the current progress in developing innovative strategies for combating multidrug-resistant A. baumannii (MDRAB) infections.
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Complete Genome Sequencing of Acinetobacter baumannii Strain K50 Discloses the Large Conjugative Plasmid pK50a Encoding Carbapenemase OXA-23 and Extended-Spectrum β-Lactamase GES-11. Antimicrob Agents Chemother 2018; 62:AAC.00212-18. [PMID: 29463529 DOI: 10.1128/aac.00212-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 02/03/2018] [Indexed: 12/21/2022] Open
Abstract
Multidrug-resistant (MDR) Acinetobacter baumannii strains appeared as serious emerging nosocomial pathogens in clinical environments and especially in intensive care units (ICUs). A. baumannii strain K50, recovered from a hospitalized patient in Kuwait, exhibited resistance to carbapenems and additionally to ciprofloxacin, chloramphenicol, sulfonamides, amikacin, and gentamicin. Genome sequencing revealed that the strain possesses two plasmids, pK50a (79.6 kb) and pK50b (9.5 kb), and a 3.75-Mb chromosome. A. baumannii K50 exhibits an average nucleotide identity (ANI) of 99.98% to the previously reported Iraqi clinical isolate AA-014, even though the latter strain lacked plasmid pK50a. Strain K50 belongs to sequence type 158 (ST158) (Pasteur scheme) and ST499 (Oxford scheme). Plasmid pK50a is a member of the Aci6 (replication group 6 [RG6]) group of Acinetobacter plasmids and carries a conjugative transfer module and two antibiotic resistance gene regions. The transposon Tn2008 carries the carbapenemase gene blaOXA-23, whereas a class 1 integron harbors the resistance genes blaGES-11, aacA4, dfrA7, qacEΔ1, and sul1, conferring resistance to all β-lactams and reduced susceptibility to carbapenems and resistance to aminoglycosides, trimethoprim, quaternary ammonium compounds, and sulfamethoxazole, respectively. The class 1 integron is flanked by MITEs (miniature inverted-repeat transposable elements) delimiting the element at its insertion site.
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