Local Dissemination of Multidrug-ResistantAcinetobacter baumanniiClones in a Thai Hospital

Abstract

A total of 83 Acinetobacter baumannii isolates from patients attending a tertiary care university hospital in Thailand were investigated for their clonal relatedness, antimicrobial susceptibility profiles, and integron carriage. Susceptibility profiles showed that 56 (67%) of these isolates exhibited multiple drug resistance (MDR). Pulsed-field gel electrophoresis (PFGE) showed that 73% of these resistant isolates were clustered into three predominant PFGE types: 6, 7, and 36. This suggested that the high number of isolates exhibiting MDR phenotypes observed in the hospital is, to some extent, due to the spread of these three resistant clones. Class 1 integrase genes were detected in all MDR isolates belonging to PFGE type 6, most MDR isolates belonging to PFGE type 7 and none of the isolates belonging to PFGE type 36. Five different class 1 gene cassette arrays, dfrA1-orfC, bla(IMP-14)-aac6', aacA4- catB8-aadA1, aacC1-orfX-orfX'-aadA1a, and aacC1-orfX-orfX-orfX'-aadA1a, were identified, of which the bla(IMP-14)-aac6' array has only been found in Thai isolates. Two isolates identified in this study carried a class 2 integrase gene with a 2.2 kb cassette array containing aadA1-sat-dfrA1.