Molecular epidemiology and antimicrobial resistance phenotypes of Acinetobacter baumannii isolated from patients in three hospitals in southern Vietnam

Abstract

Multidrug resistance in the nosocomial pathogen Acinetobacter baumannii limits therapeutic options and impacts on clinical care. Resistance against carbapenems, a group of last-resort antimicrobials for treating multidrug-resistant (MDR) A. baumannii infections, is associated with the expression (and over-expression) of carbapenemases encoded by the bla OXA genes. The aim of this study was to determine the prevalence of antimicrobial-resistant A. baumannii associated with infection in three hospitals in southern Vietnam and to characterize the genetic determinants associated with resistance against carbapenems. We recovered a total of 160 A. baumannii isolates from clinical samples collected in three hospitals in southern Vietnam from 2012 to 2014. Antimicrobial resistance was common; 119/160 (74 %) of isolates were both MDR and extensively drug resistant (XDR). High-level imipenem resistance (>32 µg ml À1 ) was determined for 109/117 (91.6 %) of the XDR imipenem-nonsusceptible organisms, of which the majority (86.7 %) harboured the bla OXA-51 and bla OXA-23 genes associated with an ISAba1 element. Multiple-locus variable number tandem repeat analysis segregated the 160 A. baumannii into 107 different multiple-locus variable number tandem repeat analysis types, which described five major clusters. The biggest cluster was a clonal complex composed mainly of imipenem-resistant organisms that were isolated from all three of the study hospitals. Our study indicates a very high prevalence of MDR/XDR A. baumannii causing clinically significant infections in hospitals in southern Vietnam. These organisms commonly harboured the bla OXA-23 gene with ISAba1 and were carbapenem resistant; this resistance phenotype may explain their continued selection and ongoing transmission within the Vietnamese healthcare system.

Overexpression ofblaOXA-58Gene Driven by ISAba3is Associated with Imipenem Resistance in a ClinicalAcinetobacter baumanniiIsolate from Vietnam

“…No isolate with bla KPC gene was detected, while two isolates contained bla NDM gene (DN050 and TN078). Even though the two isolates were singletons (based on MLVA types from previous study [17]) with different phenotypes, they had close relatedness with just difference in 3/8 loci surveyed and very similar resistance determinants, especially the bla NDM gene. Therefore, the difference in resistance phenotype was mostly because of the distinguished genotype with ISAba3_bla OXA-58 in isolate DN050, compared to isolate TN078.…”

“…The first limitation involved the small sample size due to the low prevalence of clinical isolates harbouring bla OXA-58 gene in the population surveyed. The screening has been done in previous studies [17]. Secondly, we did not characterize other resistance mechanisms in A. baumannii such as the overexpression of efflux pump genes or existence of multicopy bla OXA-58 gene [7,11,47].…”

Critical analysis of antibacterial agents in clinical development

“…Combinations of different β lactamases and the accumulation of other resistance determinants, such as aminoglycoside modifying enzymes, porin deficiencies, efflux or target protein modifications, render CRAB resistant to most of the usually available antibacterial drugs and increasingly also to tigecycline and colistin. XDR and PDR isolates are routinely being reported in some countries 12,13 .…”

Patient-to-Patient Transmission of Acinetobacter baumannii Gastrointestinal Colonization in the Intensive Care Unit

“…Most previous studies that attempted to measure the fraction of Acinetobacter spp. acquisitions due to patient-to-patient transmission have been limited and involved the use of clinical cultures only (8,9).…”