Emergence of different Acinetobacter baumannii clones in a Croatian hospital and correlation with antibiotic susceptibility

et al. 2021

IJERPH

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Carbapenem-resistant Acinetobacter baumannii is a significant health problem worldwide. A multicenter study on A. baumannii was performed to investigate the molecular epidemiology and genetic background of carbapenem resistance of A. baumannii isolates collected from 2014–2017 in Austria. In total, 117 non-repetitive Acinetobacter spp. assigned to A. baumannii (n = 114) and A. pittii (n = 3) were collected from four centers in Austria. The isolates were uniformly resistant to piperacillin/tazobactam, ceftazidime, and carbapenems, and resistance to imipenem and meropenem was 97.4% and 98.2%, respectively. The most prominent OXA-types were OXA-58-like (46.5%) and OXA-23-like (41.2%), followed by OXA-24-like (10.5%), with notable regional differences. Carbapenem-hydrolyzing class D carbapenemases (CHDLs) were the only carbapenemases found in A.baumannii isolates in Austria since no metallo-β-lactamases (MBLs) nor KPC or GES carbapenemases were detected in any of the isolates. One-third of the isolates harbored multiple CHDLs. The population structure of A. baumannii isolates from Austria was found to be very diverse, while a total of twenty-three different sequence types (STs) were identified. The most frequent was ST195 found in 15.8%, followed by ST218 and ST231 equally found in 11.4% of isolates. Two new ST types, ST2025 and ST2026, were detected. In one A. pittii isolate, blaOXA-143-like was detected for the first time in Austria.

Section: Discussionmentioning

confidence: 78%

Diversity of Oxacillinases and Sequence Types in Carbapenem-Resistant Acinetobacter baumannii from Austria

Grisold¹,

Luxner²,

et al. 2021

IJERPH

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“…A total of 172 (123 carbapenem-resistant and 49 carbapenem-susceptible) A. baumannii strains were collected in this multicenter study (Pula General Hospital, Zagreb University Hospital Centre, Varaždin General Hospital, Sisak General Hospital, Merkur University Hospital, Dr Fran Mihaljević University Hospital for Infectious Diseases, Bjelovar General Hospital and Godan Nursing Home from Zagreb) during the 2009-2014 period from various clinical specimens and analyzed in our previous studies ( 14 , 19 , 20 ).…”

Section: Methodsmentioning

confidence: 99%

“…Augmentation of the inhibition zone around imipenem and meropenem disk by at least 7 mm in the presence of EDTA was considered to be a positive result in disk diffusion, whereas an 8-fold (three dilutions) reduction in the minimum inhibitory concentration (MIC) of imipenem or meropenem by EDTA was indicative of the production of MBL in dilution test. The genes encoding MBLs (IMP, VIM, NDM, SIM) and carbapenem-hydrolyzing oxacillinases were detected by polymerase chain reaction (PCR) and sequencing in previous studies ( 14 , 19 , 20 ).…”

Section: Methodsmentioning

confidence: 99%

False Positive Phenotypic Detection of Metallo-Beta-Lactamases in Acinetobacter Baumannii

Ladavac

Vranić-Ladavac³

et al. 2019

ACC

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SUMMARY Phenotypic detection of metallo-β-lactamases (MBLs) in Acinetobacter (A.) baumannii is a serious challenge to clinical microbiologists. MBLs are inhibited by metal chelators such as ethylenediaminetetraacetic acid) (EDTA). Production of MBLs cannot be recognized based on resistance phenotype. Therefore, phenotypic tests using EDTA are recommended. The aim of this study was to investigate the sensitivity and specificity of inhibitor based tests (EDTA) for detection of MBL. A total of 172 A. baumannii strains (123 carbapenemase positive and 49 carbapenemase negative) were analyzed. Phenotypic detection of MBLs was performed by the combined disk test with EDTA (CDT-EDTA) and EPI-dilution test (EPI-DT). Both tests were positive in all 11 isolates possessing VIM-1 MBL, showing 100% sensitivity. However, false positive results were observed in strains with class D carbapenemases using both tests, i.e. all OXA-23 and OXA-24/40 producing organisms and most OXA-58 positive strains (77% with CDT-EDTA vs . 65% with EPI-DT). False positive results can occur because oxacillinases are converted to a less active state in the presence of EDTA, leading to augmentation of the inhibition zone around the carbapenem disk or reduction of carbapenem minimum inhibitory concentrations. This study showed high sensitivity but low specificity of phenotypic methods in the detection of MBLs.

“…Carbapenem resistance in A. baumannii is due to production of carbapenemases of class D (CHDL), class B, or rarely class A; moreover, porin loss or upregulation of efflux pumps can contribute to the resistance phenotype [ 86 ]. Molecular analysis of carbapenemases in urinary isolates of A. baumannii in Croatia revealed the predominance of OXA-24-like CHDL from 2009 to 2011 [ 87 , 88 , 89 ], but it was outnumbered by OXA-23-like CHDL in later years [ 90 ]. Both OXA-23-like and OXA-24/40-like carbapenemases confer a high level of resistance to carbapenems, and the plasmids encoding CHDL usually contain resistance genes for aminoglycosides and fluoroquinolones [ 86 , 90 ].…”

Section: Acinetobacter Baumanniimentioning

confidence: 99%

Mechanisms of Resistance in Gram-Negative Urinary Pathogens: From Country-Specific Molecular Insights to Global Clinical Relevance

Meštrović

2021

Diagnostics

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Urinary tract infections (UTIs) are the most frequent hospital infections and among the most commonly observed community acquired infections. Alongside their clinical importance, they are notorious because the pathogens that cause them are prone to acquiring various resistance determinants, including extended-spectrum beta-lactamases (ESBL); plasmid-encoded AmpC β-lactamases (p-AmpC); carbapenemases belonging to class A, B, and D; qnr genes encoding reduced susceptibility to fluoroquinolones; as well as genes encoding enzymes that hydrolyse aminoglycosides. In Escherichia coli and Klebsiella pneumoniae, the dominant resistance mechanisms are ESBLs belonging to the CTX-M, TEM, and SHV families; p-AmpC; and (more recently) carbapenemases belonging to classes A, B, and D. Urinary Pseudomonas aeruginosa isolates harbour metallo-beta-lactamases (MBLs) and ESBLs belonging to PER and GES families, while carbapenemases of class D are found in urinary Acinetobacter baumannii isolates. The identification of resistance mechanisms in routine diagnostic practice is primarily based on phenotypic tests for the detection of beta-lactamases, such as the double-disk synergy test or Hodge test, while polymerase chain reaction (PCR) for the detection of resistance genes is mostly pursued in reference laboratories for research purposes. As the emergence of drug-resistant bacterial strains poses serious challenges in the management of UTIs, this review aimed to appraise mechanisms of resistance in relevant Gram-negative urinary pathogens, to provide a detailed map of resistance determinants in Croatia and the world, and to discuss the implications of these resistance traits on diagnostic approaches. We summarized a sundry of different resistance mechanisms among urinary isolates and showed how their prevalence highly depends on the local epidemiological context, highlighting the need for tailored interventions in the field of antimicrobial stewardship.