Co-existence of bla OXA-23 and bla NDM-1 genes of Acinetobacter baumannii isolated from Nepal: antimicrobial resistance and clinical significance

摘要

Background Molecular analysis of carbapenem-resistant genes in Acinetobacter baumannii , an emerging pathogen, is less commonly reported from Nepal. In this study we determined the antibiotic susceptibility profile and genetic mechanism of carbapenem resistance in clinical isolates of A. baumannii. Methods A. baumannii were isolated from various clinical specimens and identified based on Gram staining, biochemical tests, and PCR amplification of organism specific 16S rRNA and bla _OXA-51 genes. The antibiotic susceptibility testing was performed using disc diffusion and E-test method. Multiplex PCR assays were used to detect the following β-lactamase genes: four class D carbapenem hydrolyzing oxacillinases ( bla _OXA-51, bla _OXA-23, bla _OXA-24 and bla _OXA-58). Uniplex PCRs were used to detect three class B metallo-β-lactamases genes ( bla _IMP, bla _VIM and bla _NDM-1), class C cephalosporin resistance genes ( bla _ADC), aminoglycoside resistance gene ( aphA6 ), and IS Aba1 of all isolates. Insertion sequence IS Aba125 among NDM-1 positive strains was detected. Clonal relatedness of all isolates were analyzed using repetitive sequence-based PCR (rep-PCR). Results Of total 44 analyzed isolates, 97.7% ( n =?43) were carbapenem-resistant A. baumannii (CR-AB) and 97.7% ( n =?43) were multidrug resistant A. baumannii (MDR-AB). One isolate was detected to be extremely drug resistant A. baumannii (XDR-AB). All the isolates were fully susceptible to colistin (MICs?OXA-23 gene was detected in all isolates, while bla _NDM-1 was detected in 6 isolates (13.6%). Insertion sequence, IS Aba1 was detected in all of bla _OXA-23 positive isolates. IS Aba125 was detected in all bla _NDM-1 positive strains. The bla _ADC and aphA6 genes were detected in 90.1 and 40.1%, respectively. The rep-PCR of all isolates represented 7 different genotypes. Conclusion We found high prevalence of CR-AB and MDR-AB with bla _OXA-23 gene in a tertiary care hospital in Nepal. Systemic network surveillance should be established for monitoring and controlling the spread of these resistant strains.