Characterization of metallo-β-lactamase and extended-spectrum β-lactamases producing Escherichia coli isolates from urinary tract infections in southeast of Iran

Urinary tract infection (UTI) is one of the most commonly encountered diseases in clinical settings and uropathogenic Escherichia coli (UPEC) is the major causative pathogen of UTI. The increase of antibiotic resistance among isolates of E. coli has become a main concern worldwide. The purposes of this study were to determine the phylogenetic background, prevalence and characterize of extended-spectrum β-lactamases and metallo-β-Lactamase produced by E. coli from UTIs.

Two hundred and sixteen E. coli isolates were isolated from UTI. The isolates were screened to determine the phylogenetic background and prevalence of CTX-M-15, PER, VEB, IMP and VIM genes by PCR. The antimicrobial susceptibility of isolates was determined by disk diffusion and broth micro-dilution methods. The isolates were screened using a double-disc synergy test.

Phylotyping of isolates revealed that isolates segregated in phylo-groups A (40.74%), B1 (7.87%), B2 (18.05%) and D (33.34%). By disk diffusion test 61.57% of isolates were resistant to cefotaxime, 35.64% to ceftazidime, 26.38% to aztreonam, 16.66% to cefepime and 6.48% to imipenem. Among the studied ESBL isolates, 72.41% isolates were positive for the CTX-M-15 gene. None of the isolates were positive for IMP, VIM, PER and VEB genes.

The ESBL-producing strains were associated with shifts in phylogenetic distribution toward none-B2 phylo-groups and they mainly belonged to A and D groups.