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Tiseo G, Galfo V, Falcone M. What is the clinical significance of 'heteroresistance' in nonfermenting Gram-negative strains? Curr Opin Infect Dis 2023; 36:555-563. [PMID: 37729656 PMCID: PMC10624410 DOI: 10.1097/qco.0000000000000964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
PURPOSE OF REVIEW The aim of this study was to discuss the potential clinical significance of heteroresistance in nonfermenting Gram-negative bacilli (GNB). RECENT FINDINGS Recently, heteroresistance has been considered potentially responsible for clinical failure in Acinetobacter baumannii infections. This raised a scientific debate, still open, about the potential clinical significance of heteroresistance in nonfermenting GNB. SUMMARY We reviewed the literature of last 20 years and found a limited number of studies evaluating the relationship between heteroresistance and clinical outcome in nonfermenting GNB. Unlike Gram-positive bacteria, heteroresistance is reported in a significant proportion of nonfermenting GNB with some studies describing it in all tested strains and for several antibiotics (including tigecycline, carbapenems, levofloxacin, cefiderocol, colistin). One important issue is the need for validated detection method since the population analysis profile test, that is considered the gold standard, requires high costs and time. Studies evaluating the correlation between heteroresistance and clinical outcome are contrasting and have several limitations. Although in-vitro detection of heteroresistance in nonfermenting GNB has not been associated with in-vivo treatment failure, its presence may suggest to prefer combination regimens instead monotherapy when treating infections by nonfermenters. Further studies are needed to clarify the clinical significance of heteroresistance.
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Affiliation(s)
- Giusy Tiseo
- Infectious Diseases Unit, Department of Clinical and Experimental Medicine, Azienda Ospedaliero Universitaria Pisana, University of Pisa, Pisa, Italy
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Roch M, Sierra R, Andrey DO. Antibiotic heteroresistance in ESKAPE pathogens, from bench to bedside. Clin Microbiol Infect 2023; 29:320-325. [PMID: 36270588 DOI: 10.1016/j.cmi.2022.10.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 09/23/2022] [Accepted: 10/13/2022] [Indexed: 11/27/2022]
Abstract
BACKGROUND Heteroresistance refers to subpopulation-mediated differential antimicrobial susceptibility within a clonal bacterial population. Usually, it designates a resistant subpopulation identified within an isolate considered susceptible by classical antimicrobial susceptibility testing. Heteroresistance lacks a uniform microbiological definition for diagnostic laboratories, and its clinical impact remains unclear for most bacterial species. OBJECTIVES This narrative review aims to provide a practical overview on the latest developments in the field of heteroresistance for both clinical microbiologists and physicians, with a particular focus on ESKAPE pathogens. SOURCES A literature search was performed on Pubmed and Google with the key words heteroresistance (heterogeneity OR heterogeneous) AND antibiotic resistance. Among the 836 publications selected based on their abstracts, the most relevant for the detection, epidemiology and clinical impact of heteroresistance in ESKAPE pathogens are discussed here. CONTENT Heteroresistance is only clearly defined for heterogeneous vancomycin intermediate Staphylococcus aureus. We compiled a larger microbiological definition to be applicable to other bacterial species and antibiotics in the clinical context. We highlighted the key technical points of population analysis profile, which is the reference standard for detecting heteroresistance. Heteroresistance to polymyxins, β-lactams (carbapenems, cefiderocol), fosfomycin, tigecycline and aminoglycosides is frequently reported in multidrug-resistant gram-negative pathogens. Treatment failure due to heteroresistance has been described in case reports or retrospective studies, so far confirmed by meta-analyses in the case of heterogeneous vancomycin intermediate S. aureus only. Finally, to treat pandrug-resistant bacterial infections, the option of targeting susceptible subpopulations of resistant isolates using tailored antibiotic combinations is also discussed. IMPLICATIONS Systematic heteroresistance screening by clinical laboratories is not currently recommended. Nevertheless, we should be aware of this phenomenon, and in specific cases, such as treatment failure, heteroresistance should be tested by reference laboratories. Additional studies using standardized methods are needed to improve our understanding of heteroresistance and further assess its clinical impact.
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Affiliation(s)
- Mélanie Roch
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Roberto Sierra
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Division of Infectious Diseases, Department of Medicine, Geneva University Hospitals and Medical School, Geneva, Switzerland
| | - Diego O Andrey
- Division of Infectious Diseases, Department of Medicine, Geneva University Hospitals and Medical School, Geneva, Switzerland; Division of Laboratory Medicine, Department of Diagnostics, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
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Whole-Genome Sequence Analysis of Carbapenem-Heteroresistant Klebsiella pneumoniae and Escherichia coli Isolates. Curr Microbiol 2022; 79:384. [DOI: 10.1007/s00284-022-03087-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
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Performance of Fully Automated Antimicrobial Disk Diffusion Susceptibility Testing Using Copan WASP Colibri Coupled to the Radian In-Line Carousel and Expert System. J Clin Microbiol 2021; 59:e0077721. [PMID: 34160274 PMCID: PMC8373016 DOI: 10.1128/jcm.00777-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The purpose of the present study was to assess the agreement at the categorical level between the Vitek 2 system and the Colibri coupled to the Radian under real routine laboratory conditions. The 675 nonduplicate clinical strains included in this study (249 Enterobacterales isolates, 198 Pseudomonas aeruginosa, 107 Staphylococcus aureus, 78 coagulase-negative staphylococci, 38 Enterococcus faecalis, and 5 Enterococcus faecium) were isolated from nonconsecutive clinical samples referred to our laboratory between June and November 2020. In addition, 43 carbapenemase-producing Enterobacterales (CPE) formerly identified and stored in our laboratory were added to the panel, for a total of 718 strains. The overall categorical agreements between the two compared methods were 99.3% (4,350/4,380; 95% CI 99% to 99.5%); 98.6% (2,147/2,178; 95% CI 98.0% to 99.0%); 99.4% (1,839/1,850; 95% CI 98.9% to 99.7%); and 99.4% (342/344; 95% CI 97.9% to 99.8%) for Enterobacterales, P. aeruginosa, Staphylococcus spp., and Enterococcus spp., respectively. The most important cause of the very major errors encountered on the Vitek 2 for P. aeruginosa (62%, 13/21) was related to the presence of heteroresistant populations. Among the 43 CPE included in this study, one OXA-48-like, and one OXA-181-like were missed by the Vitek 2, even by rigorously applying the CPE screening cutoffs defined by EUCAST. The Colibri coupled to the Radian provide a fully automated solution for antimicrobial disk diffusion susceptibility testing with an accuracy that is equal to or better than that of the Vitek 2 system.
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de Azevedo FKSF, Dutra V, Nakazato L, Mello CM, Pepato MA, de Sousa ATHI, Takahara DT, Hahn RC, Souto FJD. Molecular epidemiology of multidrug-resistant Acinetobacter baumannii infection in two hospitals in Central Brazil: the role of ST730 and ST162 in clinical outcomes. J Med Microbiol 2018; 68:31-40. [PMID: 30516469 DOI: 10.1099/jmm.0.000853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Acinetobacter baumannii is a major cause of multidrug-resistant nosocomial infections. The characteristics of A. baumannii at two hospitals in a city in Central Brazil are described by analysing the phenotypes and molecular profiles of isolates recovered from 87 patients. METHODOLOGY The isolates were identified and their antimicrobial susceptibility was evaluated using the the Bact/Alert 3D and Vitek2 methods. Patients' clinical data were obtained from medical files. Genes associated with resistance to carbapenems were analysed by multilocus sequence typing, clinical and bacteriological variables were analysed by descriptive statistics, and logistic models were generated to adjust the associations. RESULTS Sixty-four (73.5 %) out of 87 A. baumannii isolates analysed were from patients in intensive care. The mortality rate was 43.7 %. Eighty (91.9 %) isolates were resistant to imipenem and 86 were susceptible to colistin (98.8 %). The blaOXA-23 gene (78.2 %) and its upstream insertion ISAba1 (55.2 %) were predominant, followed by blaOXA-24 (55.2 %) and blaOXA-143 (28.7 %). The blaOXA-23 gene and ISAba1 were independently associated with resistance to imipenem (P<0.05). There were 13 different sequence types (STs) among the 35 isolates. ST1 (nine; 25.7 %), ST162 (eight; 22.8 %) and ST730 (six; 17.1 %) were the most common, and four new STs were identified. The isolates were grouped into five clonal complexes (CC1, CC15, CC79, CC108 and CC162) plus a singleton using eburst. CONCLUSION Respiratory infection, age >60 years and use of noradrenaline were factors associated with fatality. ST730 (CC79) was associated with higher mortality (P<0.05) and ST162 (CC162) was associated with increased survival probability (P<0.05).
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Affiliation(s)
| | - Valéria Dutra
- 2Laboratory of Veterinary Microbiology and Molecular Biology, College of Veterinary Medicine, Federal University of Mato Grosso, Mato Grosso, Brazil
| | - Luciano Nakazato
- 2Laboratory of Veterinary Microbiology and Molecular Biology, College of Veterinary Medicine, Federal University of Mato Grosso, Mato Grosso, Brazil
| | - Camila Martines Mello
- 1College of Medicine, Júlio Muller Hospital University, Federal University of Mato Grosso, Mato Grosso State, Brazil
| | - Marco Andrey Pepato
- 1College of Medicine, Júlio Muller Hospital University, Federal University of Mato Grosso, Mato Grosso State, Brazil
| | | | - Doracilde Terume Takahara
- 1College of Medicine, Júlio Muller Hospital University, Federal University of Mato Grosso, Mato Grosso State, Brazil
| | - Rosane Christine Hahn
- 1College of Medicine, Júlio Muller Hospital University, Federal University of Mato Grosso, Mato Grosso State, Brazil
| | - Francisco José Dutra Souto
- 1College of Medicine, Júlio Muller Hospital University, Federal University of Mato Grosso, Mato Grosso State, Brazil
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Li P, Huang Y, Yu L, Liu Y, Niu W, Zou D, Liu H, Zheng J, Yin X, Yuan J, Yuan X, Bai C. Isolation and Whole-genome Sequence Analysis of the Imipenem Heteroresistant Acinetobacter baumannii Clinical Isolate HRAB-85. Int J Infect Dis 2017; 62:94-101. [PMID: 28705755 DOI: 10.1016/j.ijid.2017.07.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 06/02/2017] [Accepted: 07/04/2017] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVES Heteroresistance is a phenomenon in which there are various responses to antibiotics from bacterial cells within the same population. Here, we isolated and characterised an imipenem heteroresistant Acinetobacter baumannii strain (HRAB-85). METHODS The genome of strain HRAB-85 was completely sequenced and analysed to understand its antibiotic resistance mechanisms. Population analysis and multilocus sequence typing were performed. RESULTS Subpopulations grew in the presence of imipenem at concentrations of up to 64μg/mL, and the strain was found to belong to ST208. The total length of strain HRAB-85 was 4,098,585bp with a GC content of 39.98%. The genome harboured at least four insertion sequences: the common ISAba1, ISAba22, ISAba24, and newly reported ISAba26. Additionally, 19 antibiotic-resistance genes against eight classes of antimicrobial agents were found, and 11 genomic islands (GIs) were identified. Among them, GI3, GI10, and GI11 contained many ISs and antibiotic-resistance determinants. CONCLUSIONS The existence of imipenem heteroresistant phenotypes in A. baumannii was substantiated in this hospital, and imipenem pressure, which could induce imipenem-heteroresistant subpopulations, may select for highly resistant strains. The complete genome sequencing and bioinformatics analysis of HRAB-85 could improve our understanding of the epidemiology and resistance mechanisms of carbapenem-heteroresistant A. baumannii.
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Affiliation(s)
- Puyuan Li
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China
| | - Yong Huang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Lan Yu
- Department of Gastroenterology, Navy General Hospital, 6 Fucheng Road, Beijing 100048, China
| | - Yannan Liu
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China
| | - Wenkai Niu
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China
| | - Dayang Zou
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China
| | - Huiying Liu
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China
| | - Jing Zheng
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China
| | - Xiuyun Yin
- Department of Clinical Laboratory, 307th Hospital of PLA, Beijing 100071, China
| | - Jing Yuan
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China.
| | - Xin Yuan
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China.
| | - Changqing Bai
- Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China.
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Karampatakis T, Antachopoulos C, Tsakris A, Roilides E. Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii in Greece: an extended review (2000–2015). Future Microbiol 2017; 12:801-815. [DOI: 10.2217/fmb-2016-0200] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Carbapenem-resistant Acinetobacter baumannii (CRAB) is endemic in Greece. CRAB initially emerged in 2000 and since then, carbapenemases still have a crucial role in CRAB appearance, except for a few cases resulting from efflux pump or outer-membrane protein mechanisms. OXA-type carbapenemases present the highest prevalence worldwide and bla OXA-23-like and bla OXA-58-like are the most important genes found; VIM-yielding CRAB have also been detected, while a single CRAB isolate producing NDM has quite recently emerged in Greece. The predominant OXA-23 producers are associated with multilocus sequence typing Pasteur scheme sequence type 2 clonal strains of the international clone II. The emergence of colistin-resistant CRAB has complicated the treatment of such infections and the interpretation of susceptibility data. Infection control measures and adjusted antimicrobial treatment strategies could confine CRAB spread. The aim of this review is to go through the molecular epidemiology of CRAB, in an endemic area and highlight its potential future evolution.
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Affiliation(s)
- Theodoros Karampatakis
- Infectious Diseases Unit, 3rd Department of Pediatrics, Medical Faculty, School of Health Sciences, Aristotle University, Hippokration General Hospital, Thessaloniki, Greece
| | - Charalampos Antachopoulos
- Infectious Diseases Unit, 3rd Department of Pediatrics, Medical Faculty, School of Health Sciences, Aristotle University, Hippokration General Hospital, Thessaloniki, Greece
| | - Athanassios Tsakris
- Microbiology Department, National & Kapodistrian University School of Medicine, Athens, Greece
| | - Emmanuel Roilides
- Infectious Diseases Unit, 3rd Department of Pediatrics, Medical Faculty, School of Health Sciences, Aristotle University, Hippokration General Hospital, Thessaloniki, Greece
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Combinatorial Pharmacodynamics of Ceftolozane-Tazobactam against Genotypically Defined β-Lactamase-Producing Escherichia coli: Insights into the Pharmacokinetics/Pharmacodynamics of β-Lactam-β-Lactamase Inhibitor Combinations. Antimicrob Agents Chemother 2016; 60:1967-73. [PMID: 26729494 DOI: 10.1128/aac.02635-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/24/2015] [Indexed: 12/25/2022] Open
Abstract
Despite a dearth of new agents currently being developed to combat multidrug-resistant Gram-negative pathogens, the combination of ceftolozane and tazobactam was recently approved by the Food and Drug Administration to treat complicated intra-abdominal and urinary tract infections. To characterize the activity of the combination product, time-kill studies were conducted against 4 strains ofEscherichia colithat differed in the type of β-lactamase they expressed. The four investigational strains included 2805 (no β-lactamase), 2890 (AmpC β-lactamase), 2842 (CMY-10 β-lactamase), and 2807 (CTX-M-15 β-lactamase), with MICs to ceftolozane of 0.25, 4, 8, and >128 mg/liter with no tazobactam, and MICs of 0.25, 1, 4, and 8 mg/liter with 4 mg/liter tazobactam, respectively. All four strains were exposed to a 6 by 5 array of ceftolozane (0, 1, 4, 16, 64, and 256 mg/liter) and tazobactam (0, 1, 4, 16, and 64 mg/liter) over 48 h using starting inocula of 10(6)and 10(8)CFU/ml. While ceftolozane-tazobactam achieved bactericidal activity against all 4 strains, the concentrations of ceftolozane and tazobactam required for a ≥3-log reduction varied between the two starting inocula and the 4 strains. At both inocula, the Hill plots (R(2)> 0.882) of ceftolozane revealed significantly higher 50% effective concentrations (EC50s) at tazobactam concentrations of ≤4 mg/liter than those at concentrations of ≥16 mg/liter (P< 0.01). Moreover, the EC50s at 10(8)CFU/ml were 2.81 to 66.5 times greater than the EC50s at 10(6)CFU/ml (median, 10.7-fold increase;P= 0.002). These promising results indicate that ceftolozane-tazobactam achieves bactericidal activity against a wide range of β-lactamase-producingE. colistrains.
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Yang H, Chen G, Hu L, Liu Y, Cheng J, Ye Y, Li J. Enhanced efficacy of imipenem-colistin combination therapy against multiple-drug-resistant Enterobacter cloacae: in vitro activity and a Galleria mellonella model. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2016; 51:70-75. [PMID: 26906264 DOI: 10.1016/j.jmii.2016.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 11/11/2015] [Accepted: 01/17/2016] [Indexed: 11/29/2022]
Abstract
BACKGROUND/PURPOSE To investigate the in vitro and in vivo activity of imipenem-colistin combination against multidrug-resistant Enterobacter cloacae infections in order to determine whether it should be explored further. METHODS The antimicrobial activity of colistin alone and in combination with imipenem was assessed versus an imipenem-susceptible isolate, E. cloacae GN1059, or an imipenem-resistant strain, E. cloacae GN0791, isolated in Anhui, China. The potential synergy of imipenem-colistin was evaluated using a checkerboard assay, as well as static time-kill experiments at 1× and 2× minimum inhibitory concentration (MIC). A simple invertebrate model (Galleria mellonella) was developed to assess the in vivo efficacy of imipenem-colistin in treating E. cloacae infection. RESULTS In checkerboard assays, synergy (defined as a fractional inhibitory concentration index of ≤ 0.5) was observed between imipenem and colistin for both isolates tested. In time-kill assays, the combination of imipenem-colistin at 1× or 2× MIC resulted in complete killing of both strains. In the G. mellonella larvae model infected with lethal doses of E. cloacae, the combination therapy led to significantly increased survival of the larvae as compared with imipenem or colistin monotherapy alone (p < 0.05). CONCLUSION This is the first report demonstrating the efficacy of antimicrobial agents in the G. mellonella larvae model of infections caused by E. cloacae. Our study suggested that imipenem-colistin combination was highly active against E. cloacae both in vitro and in the simple invertebrate model, and provided preliminary in vivo evidence that such combination might be useful therapeutically.
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Affiliation(s)
- Haifei Yang
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Guosheng Chen
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Lifen Hu
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Yanyan Liu
- Department of Molecular Biology, Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Department of Molecular Biology, Anhui Center for Surveillance of Bacterial Resistance, Hefei, China
| | - Jun Cheng
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Ying Ye
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China; Department of Molecular Biology, Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Department of Molecular Biology, Anhui Center for Surveillance of Bacterial Resistance, Hefei, China
| | - Jiabin Li
- Department of Infectious Disease, The First Affiliated Hospital of Anhui Medical University, Hefei, China; Department of Molecular Biology, Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Department of Molecular Biology, Anhui Center for Surveillance of Bacterial Resistance, Hefei, China; Department of Infectious Diseases, Chaohu Hospital of Anhui Medical University, Hefei, China.
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García-Salguero C, Rodríguez-Avial I, Picazo JJ, Culebras E. Can Plazomicin Alone or in Combination Be a Therapeutic Option against Carbapenem-Resistant Acinetobacter baumannii? Antimicrob Agents Chemother 2015; 59:5959-66. [PMID: 26169398 PMCID: PMC4576036 DOI: 10.1128/aac.00873-15] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Accepted: 07/06/2015] [Indexed: 12/26/2022] Open
Abstract
Nosocomial pathogens can be associated with a variety of infections, particularly in intensive care units (ICUs) and in immunocompromised patients. Usually these pathogens are resistant to multiple drugs and pose therapeutic challenges. Among these organisms, Acinetobacter baumannii is one of the most frequent being encountered in the clinical setting. Carbapenems are very useful to treat infections caused by these drug-resistant Gram-negative bacilli, but carbapenem resistance is increasing globally. Combination therapy is frequently given empirically for hospital-acquired infections in critically ill patients and is usually composed of an adequate beta-lactam and an aminoglycoside. The purpose of this study was to evaluate the in vitro activity of plazomicin against carbapenem-resistant Acinetobacter baumannii. Amikacin was used as a comparator. The activity of plazomicin in combination with several different antibiotics was tested by disk diffusion, the checkerboard method, and time-kill studies. Synergy was consistently observed with carbapenems (meropenem and/or imipenem) along with plazomicin or amikacin. When the aminoglycosides were combined with other classes of antibiotics, synergy was observed in some cases, depending on the strain and the antibiotic combination; importantly, there was no antagonism observed in any case. These findings indicate the potential utility of plazomicin in combination with other antibiotics (mainly carbapenems) for the treatment of A. baumannii infections, including those caused by carbapenem-resistant isolates.
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Affiliation(s)
| | | | - Juan J Picazo
- Microbiology Department, Hospital Clínico San Carlos, Madrid, Spain
| | - Esther Culebras
- Microbiology Department, Hospital Clínico San Carlos, Madrid, Spain
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Abstract
"Heteroresistance" describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic. Unfortunately, a lack of standard methods to determine heteroresistance has led to inappropriate use of this term. Heteroresistance has been recognized since at least 1947 and occurs in Gram-positive and Gram-negative bacteria. Its clinical relevance may be considerable, since more resistant subpopulations may be selected during antimicrobial therapy. However, the use of nonstandard methods to define heteroresistance, which are costly and involve considerable labor and resources, precludes evaluating the clinical magnitude and severity of this phenomenon. We review the available literature on antibiotic heteroresistance and propose recommendations for definitions and determination criteria for heteroresistant bacteria. This will help in assessing the global clinical impact of heteroresistance and developing uniform guidelines for improved therapeutic outcomes.
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Mei S, Gao Y, Zhu C, Dong C, Chen Y. Research of the heteroresistance of Pseudomonas aeruginosa to imipenem. Int J Clin Exp Med 2015; 8:6129-6132. [PMID: 26131216 PMCID: PMC4483920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/16/2015] [Indexed: 06/04/2023]
Abstract
Pseudomonas aeruginosa (PA) plays plays an important role in nosocomial infection. To explore the heteroresistance of PA to imipenem (IMP), we detected the sensitivity of 140 strains of PA to IMP using the KB method and VITEK method. Combined with resistance mutation analysis, the heteroresistance of PA to IMP was determined. Whilst, the double disk synergy test and SYBGreen RT-PCR for efflux pump were performed in IMP-heteroresistant PA strains. In this study, we confirmed 20 IMP-heteroresistant strains. The double disk synergy tests suggested that none of 20 heteroresistant PA strains produced metalloenzyme. The SYBGreen quantitative RT-PCR revealed that the MexAB expression level of efflux pump in IMP-heteroresistant PA was significantly higher than that in the IMP-sensitive strains (P<0.05), while there was no significantly different between the MexCD expression between resistant strains and sensitive strains (P<0.05). We believe that the clinicians should pay more attention to the PA heteroresistance to IMP, and the heteroesistance of PA to IMP is related to high expression in the MexAB of PA efflux pump.
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Affiliation(s)
- Shencong Mei
- Department of Admission, Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China
| | - Yulu Gao
- Department of Laboratory Medicine, Kunshan Hospital Affiliated to Nanjing University of Traditional Chinese MedicineKunshan 215300, Jiangsu Province, China
| | - Changtai Zhu
- Department of Transfusion, Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China
- Department of Laboratory Medicine, Changzhou Tumor Hospital Soochow UniversitySuzhou 213001, China
| | - Chunlei Dong
- Department of Laboratory Medicine, Changzhou Tumor Hospital Soochow UniversitySuzhou 213001, China
| | - Yawen Chen
- Department of Nursing, Shanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghai 200233, China
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Rapid induction of high-level carbapenem resistance in heteroresistant KPC-producing Klebsiella pneumoniae. Antimicrob Agents Chemother 2015; 59:3281-9. [PMID: 25801565 DOI: 10.1128/aac.05100-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 03/15/2015] [Indexed: 11/20/2022] Open
Abstract
Enterobacteriaceae strains producing the Klebsiella pneumoniae carbapenemase (KPC) have disseminated worldwide, causing an urgent threat to public health. KPC-producing strains often exhibit low-level carbapenem resistance, which may be missed by automated clinical detection systems. In this study, eight Klebsiella pneumoniae strains with heterogeneous resistance to imipenem were used to elucidate the factors leading from imipenem susceptibility to high-level resistance as defined by clinical laboratory testing standards. Time-kill analysis with an inoculum as low as 3 × 10(6) CFU/ml and concentrations of imipenem 8- and 16-fold higher than the MIC resulted in the initial killing of 99.9% of the population. However, full recovery of the population occurred by 20 h of incubation in the same drug concentrations. Population profiles showed that recovery was mediated by a heteroresistant subpopulation at a frequency of 2 × 10(-7) to 3 × 10(-6). Samples selected 2 h after exposure to imipenem were as susceptible as the unexposed parental strain and produced the major outer membrane porin OmpK36. However, between 4 to 8 h after exposure, OmpK36 became absent, and the imipenem MIC increased at least 32-fold. Individual colonies isolated from cultures after 20 h of exposure revealed both susceptible and resistant subpopulations. Once induced, however, the high-level imipenem resistance was maintained, and OmpK36 remained unexpressed even without continued carbapenem exposure. This study demonstrates the essential coordination between blaKPC and ompK36 expression mediating high-level imipenem resistance from a population of bacteria that initially exhibits a carbapenem-susceptibility phenotype.
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Zavascki AP, Falci DR, da Silva RCF, Dalarosa MG, Ribeiro VB, Rozales FP, Luz DI, Magagnin CM, Vieira FJ, Sampaio JM, Barth AL. Heteroresistance to carbapenems in New Delhi metallo-β-lactamase-1-producing isolates: a challenge for detection? Infect Control Hosp Epidemiol 2015; 35:751-2. [PMID: 24799663 DOI: 10.1086/676442] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Alexandre P Zavascki
- Infectious Diseases Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
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15
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Nodari CS, Ribeiro VB, Barth AL. Imipenem heteroresistance: high prevalence among Enterobacteriaceae
Klebsiella pneumoniae carbapenemase producers. J Med Microbiol 2015; 64:124-126. [DOI: 10.1099/jmm.0.081869-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Carolina Silva Nodari
- Laboratório de Pesquisa em Resistência Bacteriana - LABRESIS, Centro de Pesquisa Experimental, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, Brazil
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | | | - Afonso Luis Barth
- Laboratório de Pesquisa em Resistência Bacteriana - LABRESIS, Centro de Pesquisa Experimental, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, Brazil
- Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
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Impact of carbapenem heteroresistance among clinical isolates of invasive Escherichia coli in Chongqing, southwestern China. Clin Microbiol Infect 2014; 21:469.e1-10. [PMID: 25649300 DOI: 10.1016/j.cmi.2014.12.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 12/09/2014] [Accepted: 12/13/2014] [Indexed: 11/21/2022]
Abstract
Although heteroresistance is common in a wide range of microorganisms, carbapenem heteroresistance among invasive Escherichia coli infections has not been reported. The objective of this study was to evaluate the clinical significance of carbapenem heteroresistance and to identify risk factors for its acquisition. A case-control study was conducted at a 3200-bed teaching hospital in Chongqing, southwestern China. Successive and non-duplicate nosocomial E. coli isolates (n = 332) were obtained from July 2011 to June 2013. Bloodstream isolates made up 50.6% of the strains collected. The rates of heteroresistance were 25.0% to imipenem, 17.2% to ertapenem, and 3.9% to meropenem. The population analysis profile revealed the presence of subpopulations with higher carbapenem resistance, showing MICs ranging from 2.0-128.0mg/L. Male gender, invasive intervention, antibiotic use and bacterial extended-spectrum β-lactamase (ESBL) production contributed to invasive infections by carbapenem-heteroresistant E. coli (CHEC). The production of ESBL was identified as the common independent risk factor for heteroresistance to both ertapenem and imipenem. Pulsed-field gel electrophoresis revealed clonal diversity among the CHEC isolates. Most importantly, characterization of two successive E. coli strains isolated from the same patient indicated that carbapenem resistance evolved from heteroresistance. In conclusion, the high prevalence of heteroresistance to carbapenem among invasive E. coli merits great attention. Routine detection of ESBLs and the prudent use of imipenem and ertapenem are advocated. The early targeted intervention should be formulated to reduce CHEC infection and carbapenem resistance of E. coli.
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Durante-Mangoni E, Utili R, Zarrilli R. Combination therapy in severe Acinetobacter baumannii infections: an update on the evidence to date. Future Microbiol 2014; 9:773-89. [DOI: 10.2217/fmb.14.34] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
ABSTRACT: Acinetobacter baumannii is a drug-resistant Gram-negative pathogen increasingly causing hospital-acquired infections in critically ill patients. In this review, we summarize the current mechanisms of antimicrobial resistance in A. baumannii and describe in detail recent in vitro and in vivo experimental data on the activity of antimicrobial combinations against this microorganism. We then introduce the rationale for the use of combination antibiotic therapy in resistant A. baumannii infections. Finally, we present and critically discuss both uncontrolled clinical studies and the few randomized clinical trials of combination antimicrobial therapy for these infections, with a special focus on ongoing multinational trials and optimal approach to future research in this field.
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Affiliation(s)
- Emanuele Durante-Mangoni
- Internal Medicine, University of Naples S.U.N. & AORN dei Colli, Monaldi Hospital, Via L. Bianchi, Naples, Italy
| | - Riccardo Utili
- Internal Medicine, University of Naples S.U.N. & AORN dei Colli, Monaldi Hospital, Via L. Bianchi, Naples, Italy
| | - Raffaele Zarrilli
- Department of Public Health, University of Naples Federico II, Naples, Italy
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Population analysis of Escherichia coli isolates with discordant resistance levels by piperacillin-tazobactam broth microdilution and agar dilution testing. Antimicrob Agents Chemother 2013; 58:1779-81. [PMID: 24342642 DOI: 10.1128/aac.02181-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Population analysis was performed for 42 Escherichia coli isolates to determine whether heterogeneity of resistance was a factor in piperacillin-tazobactam category differences between agar dilution and broth microdilution. Of 20 isolates discordant between methods, 80% were heterogeneous. Of 22 isolates in agreement, 59% were homogeneous. Heterogeneity and homogeneity rates for those in agreement were significantly different from those that were discordant (P value, 0.010). Heterogeneity of resistance expression appears to be an important factor in category differences observed between broth microdilution and agar dilution for piperacillin-tazobactam.
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19
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Growth retardation, reduced invasiveness, and impaired colistin-mediated cell death associated with colistin resistance development in Acinetobacter baumannii. Antimicrob Agents Chemother 2013; 58:828-32. [PMID: 24247145 DOI: 10.1128/aac.01439-13] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Two colistin-susceptible/colistin-resistant (Col(s)/Col(r)) pairs of Acinetobacter baumannii strains assigned to international clone 2, which is prevalent worldwide, were sequentially recovered from two patients after prolonged colistin administration. Compared with the respective Col(s) isolates (Ab248 and Ab299, both having a colistin MIC of 0.5 μg/ml), both Col(r) isolates (Ab249 and Ab347, with colistin MICs of 128 and 32 μg/ml, respectively) significantly overexpressed pmrCAB genes, had single-amino-acid shifts in the PmrB protein, and exhibited significantly slower growth. The Col(r) isolate Ab347, tested by proteomic analysis in comparison with its Col(s) counterpart Ab299, underexpressed the proteins CsuA/B and C from the csu operon (which is necessary for biofilm formation). This isolate also underexpressed aconitase B and different enzymes involved in the oxidative stress response (KatE catalase, superoxide dismutase, and alkyl hydroperoxide reductase), suggesting a reduced response to reactive oxygen species (ROS) and, consequently, impaired colistin-mediated cell death through hydroxyl radical production. Col(s) isolates that were indistinguishable by macrorestriction analysis from Ab299 caused six sequential bloodstream infections, and isolates indistinguishable from Ab248 caused severe soft tissue infection, while Col(r) isolates indistinguishable from Ab347 and Ab249 were mainly colonizers. In particular, a Col(s) isolate identical to Ab299 was still invading the bloodstream 90 days after the colonization of this patient by Col(r) isolates. These observations indicate considerably lower invasiveness of A. baumannii clinical isolates following the development of colistin resistance.
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20
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Hermes DM, Pormann Pitt C, Lutz L, Teixeira AB, Ribeiro VB, Netto B, Martins AF, Zavascki AP, Barth AL. Evaluation of heteroresistance to polymyxin B among carbapenem-susceptible and -resistant Pseudomonas aeruginosa. J Med Microbiol 2013; 62:1184-1189. [PMID: 23699064 DOI: 10.1099/jmm.0.059220-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One hundred and twenty-four Pseudomonas aeruginosa isolates were selected for antimicrobial susceptibility testing with anti-pseudomonal agents, MIC determination for polymyxin B and metallo-beta-lactamase detection (genes blaSPM, blaVIM-1, blaNDM-1 and blaIMP). According to the imipenem and/or meropenem susceptibility profile, a set of randomly selected isolates (12 isolates carbapenem-susceptible and 12 isolates carbapenem-resistant) were evaluated for heteroresistance to polymyxin B. Heteroresistance testing was performed by plating the isolates onto increasing concentrations of polymyxin B (from 0 to 8.0 mg l(-1)). The population analysis profile (PAP) was defined as the ratio of the number of colony-forming units on the plate with the highest concentration of polymyxin B at which bacterial growth occurred against the number of colony-forming units on the plate without antibiotic. Isolates presenting subpopulations that exhibited growth at polymyxin B concentrations ≥2 mg l(-1) were considered heteroresistant. Isolates containing subpopulations that grew at polymyxin B concentrations at least twice as high as the original MIC but <2 mg l(-1) were considered heterogeneous. Antimicrobial susceptibility testing results indicated a variable degree of susceptibility: high levels of resistance to gentamicin (30.6 %) and imipenem (29.0 %); low levels of resistance to aztreonam (1.6 %) and ciprofloxacin (4.8 %). All isolates were susceptible to polymyxin B: MIC50 and MIC90 were 1 mg l(-1) and 2 mg l(-1), respectively. Thirty-seven isolates (30 %) were carbapenem-resistant. Four isolates resistant to carbapenems were positive for blaIMP. There were no heteroresistant subpopulations in the carbapenem-susceptible group, but three isolates presented heterogeneous subpopulations. The PAP frequency ranged from 2.1×10(-4) to 6.9×10(-8). In the carbapenem-resistant group, one isolate was heteroresistant. Six isolates in this group presented heterogeneous subpopulations. In the resistant population, the PAP frequency ranged from 2.1×10(-7) to 2.6×10(-4). In this study, polymyxin B heteroresistance in P. aeruginosa was uncommon and occurred in only one carbapenem-resistant isolate, despite the fact that several isolates presented heterogeneous subpopulations with increased polymyxin B MICs.
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Affiliation(s)
- Djuli M Hermes
- Programa de Pós Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
| | | | - Larissa Lutz
- Unidade de Microbiologia, Hospital de Clínicas de Porto Alegre (HCPA), Brazil
| | - Aline B Teixeira
- Programa de Pós Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
| | | | - Bárbara Netto
- Programa de Pós Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
| | | | - Alexandre P Zavascki
- Infectious Disease Service, HCPA, Brazil
- Programa de Pós Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
| | - Afonso L Barth
- Serviço de Patologia Clínica, HCPA, Brazil
- Programa de Pós-Graduação em Ciências Farmacêuticas, UFRGS, Brazil
- Programa de Pós Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil
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21
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Virulence of Acinetobacter baumannii Exhibiting Phenotypic Heterogeneous Growth against Meropenem in a Murine Thigh Infection Model. Antibiotics (Basel) 2013; 2:73-82. [PMID: 27029293 PMCID: PMC4790299 DOI: 10.3390/antibiotics2010073] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 02/16/2013] [Accepted: 03/01/2013] [Indexed: 11/17/2022] Open
Abstract
Acinetobacter baumannii may exhibit phenotypic heterogeneous growth under exposure to antibiotics. We investigated the in vitro characteristics of A. baumannii isolates grown heterogeneously in the presence of meropenem and their virulence evaluated in experimental infections treated with meropenem. Five clinical A. baumannii isolates and the respective heterogeneously grown subpopulations were tested by agar dilution minimum inhibitory concentration (MIC) testing, pulsed field gel electrophoresis (PFGE), population analysis using meropenem and growth curves. The virulence of isolates and the therapeutic efficacy of three meropenem dosing schemes was evaluated in a neutropenic murine thigh infection model. The clinical isolates were meropenem-susceptible (MICs 1 to 4 mg/liter) and exhibited three distinct PFGE patterns. In all clinical isolates, population analysis yielded heterogeneously grown colonies. After seven subcultures in antibiotic-free media, resistant MIC levels were retained in two isolates (heteroresistant), while three isolates were reversed to susceptible MICs (persisters). Clinical isolates and heterogeneous subpopulations had similar growth rates. The heterogeneously grown A. baumannii subpopulations had reduced virulence, killing considerably fewer animals than the respective clinical isolates without treatment. The meropenem treatment outcome was similar in infections caused by the clinical and the heterogeneous isolates, irrespective to their MICs. In vitro meropenem exposure induces phenotypic heterogeneous growth in A. baumannii. Compared with the parental clinical isolates, the heterogeneously grown subpopulations exhibited lower virulence, killing fewer mice and responding equally to meropenem treatment, despite their higher MICs.
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22
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Global evolution of multidrug-resistant Acinetobacter baumannii clonal lineages. Int J Antimicrob Agents 2012; 41:11-9. [PMID: 23127486 DOI: 10.1016/j.ijantimicag.2012.09.008] [Citation(s) in RCA: 359] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 12/22/2022]
Abstract
The rapid expansion of Acinetobacter baumannii clinical isolates exhibiting resistance to carbapenems and most or all available antibiotics during the last decade is a worrying evolution. The apparent predominance of a few successful multidrug-resistant lineages worldwide underlines the importance of elucidating the mode of spread and the epidemiology of A. baumannii isolates in single hospitals, at a country-wide level and on a global scale. The evolutionary advantage of the dominant clonal lineages relies on the capability of the A. baumannii pangenome to incorporate resistance determinants. In particular, the simultaneous presence of divergent strains of the international clone II and their increasing prevalence in international hospitals further support the ongoing adaptation of this lineage to the hospital environment. Indeed, genomic and genetic studies have elucidated the role of mobile genetic elements in the transfer of antibiotic resistance genes and substantiate the rate of genetic alterations associated with acquisition in A. baumannii of various resistance genes, including OXA- and metallo-β-lactamase-type carbapenemase genes. The significance of single nucleotide polymorphisms and transposon mutagenesis in the evolution of A. baumannii has been also documented. Establishment of a network of reference laboratories in different countries would generate a more complete picture and a fuller understanding of the importance of high-risk A. baumannii clones in the international dissemination of antibiotic resistance.
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23
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Epidemiological and clinical features associated with colonisation/infection by Acinetobacter baumannii with phenotypic heterogeneous resistance to carbapenems. Int J Antimicrob Agents 2012; 40:235-8. [DOI: 10.1016/j.ijantimicag.2012.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 04/16/2012] [Accepted: 05/04/2012] [Indexed: 11/17/2022]
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24
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Fernández Cuenca F, Sánchez MDCG, Caballero-Moyano FJ, Vila J, Martínez-Martínez L, Bou G, Baño JR, Pascual A. Prevalence and analysis of microbiological factors associated with phenotypic heterogeneous resistance to carbapenems in Acinetobacter baumannii. Int J Antimicrob Agents 2012; 39:472-7. [DOI: 10.1016/j.ijantimicag.2012.01.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2011] [Revised: 12/20/2011] [Accepted: 01/19/2012] [Indexed: 10/28/2022]
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25
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Heteroresistance to cephalosporins and penicillins in Acinetobacter baumannii. J Clin Microbiol 2011; 50:721-6. [PMID: 22189112 DOI: 10.1128/jcm.05085-11] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Heteroresistance to antimicrobial agents may affect susceptibility test results and therapeutic success. In this study, we investigated heteroresistance to cephalosporins and penicillins in Acinetobacter baumannii, a major pathogen causing nosocomial infections. Two A. baumannii isolates exhibited heteroresistance to ampicillin-sulbactam, ticarcillin-clavulanic acid, cefepime, and cefpirome, showing a distinct colony morphology of circular rings within the inhibition halos. Pulsed-field gel electrophoresis (PFGE) and outer membrane protein (OMP) analysis demonstrated that subpopulations around the disks/Etest strips and the original strains all belonged to the same PFGE type and OMP profile. Population analysis profile (PAP) showed the presence of heteroresistant subpopulations with high cefepime resistance levels in two isolates (008 and 328). Interestingly, A. baumannii 008 contained two peaks: one was grown in the presence of up to 1 μg of cefepime/ml, the other apparently occurred when the concentration of cefepime was raised to 256 μg/ml. After serial passages without exposure to cefepime, the PAP curve maintained the same trend observed for the original strain of A. baumannii 008. However, the PAP curve showed a shift to relatively lower cefepime resistance (from 256 to 64 μg/ml) in A. baumannii 328 after 10 passages in antibiotic-free Mueller-Hinton agar plates. Convergence to a monotypic resistance phenotype did not occur. Growth rate analysis revealed that slower growth in resistant subpopulations may provide a strategy against antibiotic challenge. To our knowledge, this is the first report of heteroresistance to cephalosporins and penicillins in A. baumannii.
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26
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Sheng WH, Wang JT, Li SY, Lin YC, Cheng A, Chen YC, Chang SC. Comparative in vitro antimicrobial susceptibilities and synergistic activities of antimicrobial combinations against carbapenem-resistant Acinetobacter species: Acinetobacter baumannii versus Acinetobacter genospecies 3 and 13TU. Diagn Microbiol Infect Dis 2011; 70:380-6. [PMID: 21558048 DOI: 10.1016/j.diagmicrobio.2011.03.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 02/24/2011] [Accepted: 03/02/2011] [Indexed: 11/16/2022]
Abstract
Therapeutic options for the treatment of infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) are limited. In vitro activity of amikacin, ciprofloxacin, colistin (polymyxin E), ampicillin-sulbactam, and tigecycline alone and in combination with imipenem against CRAB and carbapenem-resistant Acinetobacter genospecies 3 and 13TU was investigated. Colistin (97% susceptible) and tigecycline (88% and 44% susceptible by US Food and Drug Administration [FDA] and European Committee on Antimicrobial Susceptibility Testing [EUCAST] breakpoints for Enterobacteriaceae, respectively) were the 2 most active agents against CRAB, followed by minocycline (66%), ampicillin/sulbactam (16%), and amikacin (13%). Compared with CRAB isolates, carbapenem-resistant Acinetobacter genospecies 3 and 13TU isolates had higher antimicrobial susceptible rates to ciprofloxacin (88%), amikacin (63%), tigecycline (100% by FDA breakpoint and 88% by EUCAST breakpoint for Enterobacteriaceae, respectively), minocycline (100%), and ampicillin/sulbactam (75%). For the 12 tested CRAB isolates, the checkerboard titration method demonstrated synergy between imipenem and colistin (42%), tigecycline (25%), amikacin (16%), and ampicillin/sulbactam (16%). Time-kill assays revealed antimicrobial synergism for imipenem in combination with colistin (75%), tigecycline (50%), ampicillin/sulbactam (42%), amikacin (42%), and ciprofloxacin (16%). However, antimicrobial synergism between imipenem and combined agents was not present among CRAB isolates with an imipenem MIC ≥ 32 mg/L. The combination of tigecycline and colistin showed good in vitro synergy for CRAB with high imipenem resistance. Our results demonstrate accurate identification of prevalent Acinetobacter species and highlight their different antimicrobial susceptibilities. This knowledge will enable clinicians to select appropriate regimens for treating these infections.
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Affiliation(s)
- Wang-Huei Sheng
- Department of Internal Medicine, National Taiwan University Hospital, Taipei 100, Taiwan
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Lee HY, Chen CL, Wang SB, Su LH, Chen SH, Liu SY, Wu TL, Lin TY, Chiu CH. Imipenem heteroresistance induced by imipenem in multidrug-resistant Acinetobacter baumannii: mechanism and clinical implications. Int J Antimicrob Agents 2011; 37:302-8. [PMID: 21353490 DOI: 10.1016/j.ijantimicag.2010.12.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Revised: 12/10/2010] [Accepted: 12/18/2010] [Indexed: 11/28/2022]
Abstract
Acinetobacter baumannii has emerged as a major pathogen causing nosocomial infections, particularly in critical patients admitted to the Intensive Care Unit. Increasing resistance to carbapenems in A. baumannii has been observed worldwide. Here we report the clinical impact and mechanism of imipenem heteroresistance (imipenem minimum inhibitory concentration of 6-32 μg/mL with the presence of resistant cells inside the inhibition zone of Etest strips or disks) in multidrug-resistant A. baumannii (MDR-AB). To identify risk factors associated with the emergence of imipenem heteroresistance, a retrospective case-control study was undertaken involving cases with subsequent clinical isolates of the same genotype showing loss of imipenem susceptibility and matched controls with isolates belonging to imipenem-susceptible MDR-AB. The molecular mechanism of heteroresistance was examined. From April 2006 to March 2007, 126 consecutive isolates of MDR-AB were identified from 29 patients. Switch from imipenem susceptibility to heteroresistance was more likely to occur in successive MDR-AB derived from patients who had been exposed to imipenem (length of use 10.9 ± 6.5 days for cases vs. 5.3 ± 4.8 days for controls; P=0.02). An insertion sequence (ISAba1) was found in the promoter region of a class C β-lactamase gene (bla(ADC-29)) in most imipenem-heteroresistant MDR-AB isolates. In vitro experiments indicated that imipenem heteroresistance, which was associated with overexpression of bla(ADC-29), could be induced by imipenem. Carbapenem use was the only risk factor identified for the emergence of carbapenem-heteroresistant MDR-AB. Physicians should weigh the benefits and risks of each carbapenem-based treatment in managing carbapenem-susceptible MDR-AB infection.
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Affiliation(s)
- Hao-Yuan Lee
- Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan
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28
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Carbapenem Heteroresistance in VIM-1-producing Klebsiella pneumoniae isolates belonging to the same clone: consequences for routine susceptibility testing. J Clin Microbiol 2010; 48:4089-93. [PMID: 20844213 DOI: 10.1128/jcm.01130-10] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Susceptibility results with low reproducibility by the same or different methods have been observed for metallo-beta-lactamase (MBL)-producing Enterobacteriaceae. Eighteen VIM-1-producing Klebsiella pneumoniae isolates (one per patient) belonging to a single epidemic clone in our hospital (2005 to 2008) but with different susceptibilities to carbapenems were studied. Imipenem MICs ranged from 8 to >128 mg/liter by standard CLSI microdilution, from ≤1 to >8 mg/liter by the semiautomatic Wider system, and from 0.75 to >32 mg/liter by Etest. Meropenem MICs ranged from 0.5 to 128, ≤1 to >8, and 0.38 to >32 mg/liter, respectively. Ertapenem MICs by CLSI microdilution and Etest ranged from 1 to 64 and 0.75 to >32 mg/liter, respectively. The rates of essential agreement (±1 log(2) dilution) for imipenem and meropenem MICs between the Wider system and the reference microdilution method were 45% and 49%, respectively. Those between Etest and the reference microdilution method for imipenem, meropenem, and ertapenem MICs were 33%, 67%, and 84%. The rates of very major errors for the Wider system and Etest were 33% and 28% for imipenem and 25% and 75% for meropenem, respectively. Low MIC reproducibility was observed even when the same inoculum was used (differences up to 4-fold dilutions). Heteroresistance was suspected due to the presence of colonies in the Etest inhibition zone. It was confirmed by population analysis profiles of 4 isolates displaying different imipenem MICs, with the exception of an OmpK36-porin-deficient isolate that homogeneously expressed carbapenem resistance (MIC, >128 mg/liter). Low carbapenem MIC reproducibility could be due to the presence of resistant subpopulations and variable expression of the resistance mechanisms. Since carbapenem MICs are not good markers of MBL production, reliable and reproducible phenotypic methods are needed to detect the presence of this mechanism.
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Brouwer MC, Tunkel AR, van de Beek D. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev 2010; 23:467-92. [PMID: 20610819 PMCID: PMC2901656 DOI: 10.1128/cmr.00070-09] [Citation(s) in RCA: 509] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The epidemiology of bacterial meningitis has changed as a result of the widespread use of conjugate vaccines and preventive antimicrobial treatment of pregnant women. Given the significant morbidity and mortality associated with bacterial meningitis, accurate information is necessary regarding the important etiological agents and populations at risk to ascertain public health measures and ensure appropriate management. In this review, we describe the changing epidemiology of bacterial meningitis in the United States and throughout the world by reviewing the global changes in etiological agents followed by specific microorganism data on the impact of the development and widespread use of conjugate vaccines. We provide recommendations for empirical antimicrobial and adjunctive treatments for clinical subgroups and review available laboratory methods in making the etiological diagnosis of bacterial meningitis. Finally, we summarize risk factors, clinical features, and microbiological diagnostics for the specific bacteria causing this disease.
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Affiliation(s)
- Matthijs C. Brouwer
- Department of Neurology, Center of Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands, Department of Medicine, Monmouth Medical Center, Long Branch, New Jersey
| | - Allan R. Tunkel
- Department of Neurology, Center of Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands, Department of Medicine, Monmouth Medical Center, Long Branch, New Jersey
| | - Diederik van de Beek
- Department of Neurology, Center of Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands, Department of Medicine, Monmouth Medical Center, Long Branch, New Jersey
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Characteristics of meropenem heteroresistance in Klebsiella pneumoniae carbapenemase (KPC)-producing clinical isolates of K. pneumoniae. J Clin Microbiol 2010; 48:2601-4. [PMID: 20504985 DOI: 10.1128/jcm.02134-09] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Meropenem heteroresistance was investigated in six apparently meropenem-susceptible, Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) clinical isolates, compared with that in carbapenemase-negative, meropenem-susceptible controls. In population analyses, the KPC-KP isolates grew at meropenem concentrations of 64 to 256 microg/ml. Heteroresistant colonies had significantly elevated expression of the bla(KPC) gene compared with the native populations but did not retain heteroresistance when subcultured in drug-free media. Time-kill assays indicated that meropenem alone was not bactericidal against KPC-KP but efficiently killed the control strains.
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