Molecular Characterization of Multidrug-Resistant Escherichia coli Isolates in Azerbaijan Hospitals

Abstract

Aims:

The emergence and clonal occurrence of multidrug-resistant (MDR) Escherichia coli isolates are increasing worldwide. In this study, phenotypic and genotypic characteristics of MDR E. coli isolates overexpressing efflux pump were investigated in medical centers of Azerbaijan. Two hundred nineteen consecutive and nonduplicated isolates of E. coli were collected and screened, and confirmed for extended-spectrum β-lactamase, AmpC, and carbapenemase activities and respective genes. MDR isolates were selected and subjected to efflux pump overexpression assay. Cefoxitin-nonsusceptible isolates were subjected to mutational analysis of promoter region of chromosomal ampC gene. MDR isolates with overexpressed efflux were analyzed for acrR and marR mutations and assigned to multilocus sequence typing.

Results:

Eighty (36.5%) isolates had MDR pattern, among which 16 (20%) isolates were positive for overexpressed efflux. Ninety-eight of 99 suspected isolates were positive for any β-lactamase genes, particularly CTX-M groups 1 and 9. Ten out of 33 cefoxitin-nonsusceptible isolates had mutations in promoter region of chromosomal AmpC gene, including −32T→A (n = 5), −42C→T, and −18G→A (n = 3) and −13TT and GT insertion (n = 2). Detected mutations in efflux regulatory genes include G103S and Y137H (n = 15), K62R (n = 8), S3N (n = 3), and A53E (n = 1) in marR and L109 (n = 2) and L190 (n = 1) frameshift mutations and T12M, T213I, N214T, I113V, and H115Y point mutations (n = 5) in acrR.

Conclusions:

Overexpressing efflux pump isolates belonging to sequence type (ST)131 and ST73 clones are emerging in Azerbaijan hospitals. Clonal occurrence of MDR E. coli is an alarming situation in Azerbaijan hospitals.