Emergence of ISAba1-linked oxacillinase genes among carbapenem resistantAcinetobacter baumanniiisolates in a tertiary cardiac center, Nepal

Abstract

AbstractInsertion sequence contributes to the emergence of carbapenem resistance by dissemination of carbapenemase genes and providing promoter for their overexpression. This study aims to ascertain the occurrence of ISAba1-linked OXA carbapenemase genes and its relevance to carbapenem resistance level inAcinetobacter baumannii. This hospital based descriptive study was conducted at Shahid Gangalal National Heart Center, Kathmandu, Nepal. An overall of 1,291 clinical specimens received for routine culture and antibiotic susceptibility testing throughout the study period were included in this study. Identification ofAcinetobacter baumanniiwas validated through detection of intrinsicblaOXA-51-likegene by polymerase chain reaction (PCR). Antibiotic susceptibility was tested by Kirby-Bauer disc diffusion approach and minimum inhibitory concentration (MIC) of meropenem was assessed through agar dilution method. Uniplex PCR assays were performed to detect genes encoding oxacillinases and ISAba1. Upstream association of insertion element, ISAba1to oxacillinase genes was assessed through PCR mapping strategy using ISAba1F and OXA-51R/OXA-23R primers. Out of the 340 bacteria isolated, only 40 (11.8%) wereAcinetobacter baumannii. All isolates were resistant against meropenem with MIC value ranging from 16-256 μg/ml.blaOXA-23-likegenes was present in every isolate butblaOXA-58in just two isolates (5%). All isolates had ISAba1either aboveblaOXA-23-likeorblaOXA-51-likegene. Higher MIC90value of meropenem (243.20 μg/ml) was found inA.baumanniicluster with ISAba1-linked upstream to bothblaOXA-23-likeandblaOXA-51-likegenes, thus depicting their eminent role to enhanced carbapenem resistance.Acinetobacter baumanniiisolates with ISAba1-linked oxacillinase genes are rapidly emerging in clinical settings of Nepal. Thus, medical communities need to be prepared and enable targeted approaches for managing burgeoning problem of carbapenem resistance.