Contribution of genetic factors towards cefotaxime and ciprofloxacin resistance development among Extended spectrum beta-lactamase producing-Quinolone resistant pathogenic Enterobacteriaceae

Abstract

β-lactams and quinolones are widely utilised to treat pathogenic Enterobacterial isolates worldwide. Due to improper use of these antibiotics, both ESBL producing and quinolone resistant (ESBL-QR) pathogenic bacteria have emerged. Nature of contribution of beta-lactamase (bla)/quinolone resistant (QR) genes, efflux pumps (AcrAB-TolC) over-expression and outer membrane proteins (OMPs) /porin loss/reduction and their combinations towards development of this phenotype were explored in this study. Kirby–Bauer disc diffusion method was used for phenotypic characterization of these bacteria and minimum inhibitory concentration of cefotaxime and ciprofloxacin was determined by broth micro dilution assay. Presence of bla, QR, gyrA/B genes was examined by PCR; acrB upregulation by real-time quantitative PCR and porin loss/reduction by SDS-PAGE. Based on antibiogram, phenotypic categorization of 715 non-duplicate clinical isolates was: ESBL+QR+ (n = 265), ESBL+QR- (n = 6), ESBL-QR+ (n = 346) and ESBL-QR-(n = 11). Increased OmpF/K35 and OmpC/K36 reduction, acrB up-regulation, prevalence of bla, QR genes and gyrA/B mutation was observed among the groups in following order: ESBL+QR+> ESBL-QR+> ESBL+QR-> ESBL-QR-. Presence of bla gene alone or combined porin loss and efflux pump upregulation or their combination contributed most for development of a highest level of cefotaxime resistance of ESBL+QR+ isolates. Similarly, combined presence of QR genes, porin loss/reduction, efflux pump upregulation and gyrA/B mutation contributed towards highest ciprofloxacin resistance development of these isolates.