Mutation of CarO participates in drug resistance in imipenem-resistant Acinetobacter baumannii.

Li‐Jing Zhu,Xiao‐Ying Chen,Pan‐Fei Hou

doi:10.1002/jcla.22976

Abstract

Objective Acinetobacter baumannii has become an important problem because of the high drug resistance rate. The aim of this study was to assess the antimicrobial resistance profile and explore the role of membrane porin in imipenem resistance of A baumannii.MethodsA total of 63 isolates of imipenem‐resistant A baumannii (IRAB) and 21 of imipenem‐sensitive A baumannii (ISAB) were collected. Susceptibility testing to 16 kinds of antimicrobial agents was conducted by K‐B method. PCR technique was used to detect carO and oprD genes, and sequencing was performed to compare the sequence between IRAB and ISAB. Three‐dimensional structure model of CarO protein was established.ResultsWhile ISAB isolates presented sensitive to most classes of antibiotics, isolates of IRAB displayed much higher resistance rate except tigecycline (3.2%), cefoperazone/sulbactam (28.6%), and minocycline (30.2%). All 84 isolates were observed carrying both carO and oprD genes. Further sequencing revealed important mutations of carO gene existed in IRAB in comparison with ISAB. Meanwhile, significant differences in three‐dimensional structure of carO protein molecule were also found between IRAB and ISAB.ConclusionsThe drug resistance profile of IRAB is increasingly severe in clinical settings. Mutation of CarO was identified as one of the molecular mechanisms involved in imipenem resistance in A baumannii.

Highlights

Acinetobacter baumannii, a nonfermentative, gram‐negative cocco‐ bacillus, has emerged as a ubiquitous opportunistic pathogen lead‐ ing to nosocomial infections with high morbidity and mortality.[1]
This study aims to assess the antimicrobial resistance profile and explore the role of CarO and OprD in imipenem resistance of A baumannii
Acinetobacter baumannii, which widely exists in natural soil, water, hospital environment and human skin, urogenital tract, digestive tract, and respiratory tract, is an important pathogen of nosocomial infection.[14]

Summary

| INTRODUCTION

Acinetobacter baumannii, a nonfermentative, gram‐negative cocco‐ bacillus, has emerged as a ubiquitous opportunistic pathogen lead‐ ing to nosocomial infections with high morbidity and mortality.[1] It mainly causes respiratory tract infection, as well as bacteremia, Li‐Jing Zhu and Xiao‐Ying Chen contributed to this work and should be considered co‐first authors. CarO protein, generally considered as an eight‐stranded β‐barrel protein of 29 KDa,[6] plays a key role in the influx of imipenem (but not meropenem) into A baumannii. It could be divided into two groups, CarOa and CarOb, in which CarOb was showed to be twice more specific for imipenem than CarOa.[7]. This study aims to assess the antimicrobial resistance profile and explore the role of CarO and OprD in imipenem resistance of A baumannii

| MATERIALS AND METHODS

Findings

| DISCUSSION