Detection of ISAba1 in association with a novel allelic variant of the β-lactamase ADC-82 and class D β-lactamase genes mediating carbapenem resistance among the clinical isolates of MDR A. baumannii.

The objective of the present study is to investigate the diverse resistance determinants, their association with IS mobile elements and predilection of a particular clone for such associations in A. baumannii. Fifty-four consecutive isolates collected during 2011-2012 from a tertiary care hospital were subjected to susceptibility testing followed by PCR screening of commonly reported β-lactamases and 16S rRNA methyl transferase encoding genes. The integrity of RND efflux pump related genes in their respective operons was also investigated. β-lactamase genes such as blaADC (100%), blaOXA-23 (81%), blaPER-1 (81%), blaIMP-1(31%) and blaNDM-1(15%) were found to be present more frequently while blaVIM-2 and blaOXA-24 were not observed in our study. ISAba1 was associated only with blaOXA-51-like (30%), blaOXA-23 like (55%) and blaADC like (33%). armA was found in 87% of isolates and ISAba1 linked with one novel variant of ADC namely blaADC-82, which was identified to have 15 nucleotide differences with blaADC-79 and this finding is of much significance. In many isolates efflux pump genes were not intact, resulting in severely altered effluxing functions. For the first time we have identified ISAba1 mediated disruption of adeN among the isolates of ST 195B, which would have led to over expression of AdeIJK efflux pump causing elevated resistance. MLST revealed the predominance of CC 92B (IC-IIB) and CC 447B clonal complexes. High incidence of IC-II clones, novel resistance determi...
Source: Journal of Medical Microbiology - Category: Microbiology Authors: Tags: J Med Microbiol Source Type: research