Abstract

BackgroundCarbapenem-resistant Acinetobacter baumannii poses a significant threat to hospitalized patients, as few therapeutic options remain. Thus, we investigated the molecular epidemiology and mechanism of resistance of carbapenem-resistant A.baumannii isolates in Beijing, China.MethodsCarbapenem-resistant A.baumannii isolates (n = 101) obtained between June 2009 and November 2014 were used. Multilocus sequence typing (MLST) and PCR assays for class C and D β-lactamase were performed on all isolates. S1 nuclease pulsed-field gel electrophoresis (PFGE) and Southern blot hybridization were performed to identify the resistance gene location.ResultsAll 101 A.baumannii isolates were highly resistant to frequently used antimicrobials, and were considered multidrug resistant. A total of 12 sequence types (STs) were identified, including 10 reported STs and 2 novel STs. Eighty-seven isolates were classified to clonal complex 92 (CC92), among which ST191 and ST195 were the most common STs. The blaOXA-23 gene was positive in most (n = 95) of the A.baumannii isolates. Using S1-nuclease digestion PFGE and Southern blot hybridization, 3 patterns of plasmids carrying blaOXA-23 were confirmed. ST191 and ST195 (both harboring blaOXA-23) caused outbreaks during the study period, and this is the first report of outbreaks caused by ST191 and ST195 in north China.ConclusionblaOXA-23-producing A.baumannii ST191 and ST 195 isolates can disseminate in a hospital and are potential nosocomial outbreak strains. Surveillance of imipenem-resistant A.baumannii and antimicrobial stewardship should be strengthened.

Highlights

  • Carbapenem-resistant Acinetobacter baumannii poses a significant threat to hospitalized patients, as few therapeutic options remain

  • Acinetobacter baumannii is an opportunistic pathogen involved in outbreaks occurring in burn units, surgical wards or intensive care units (ICUs), as well as important cause of nosocomial septicemia, pneumonia and urinary tract infections [1]

  • We identified ST191, ST195, ST208, ST218, ST368 and ST369 as classified into clonal complex 92 (CC92) which was the largest and most widely distributed A.baumannii clone in China [17]

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Summary

Introduction

Carbapenem-resistant Acinetobacter baumannii poses a significant threat to hospitalized patients, as few therapeutic options remain. A.baumannii is of interest due to increasing the increase in antimicrobial resistance [2] This organism is generally intrinsically resistant to many frequently-used antibiotics, including aminopenicillin, first- and second-generation cephalosporins and chloramphenicol [3, 4]. The emergent and rapid spread of carbapenem-resistant A.baumannii isolates pose a severe threat to public health and are a global concern [6]. Carbapenem resistance, such as to imipenem, increased in China from 31.0% in 2005 to 62.4% in 2014 [7]. Recent studies suggest high resistant of A.baumannii against carbapenems across the world [8,9,10,11]

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