Molecular Characterization of Extended Spectrum β-Lactamase-Producing Escherichia coli: Insights into the O25b-ST131 Clone in Mexican Urinary Tract Infections

 The urgent need for antimicrobial research to address the escalating global challenge of β-lactam antibiotic resistance, particularly in Escherichia coli-induced urinary tract infections (UTI), is underscored by the increasing resistance to ciprofloxacin in Latin America. This issue has led to a heightened dependence on alternative therapeutics, such as cephalosporins. The identification of extended-spectrum β-lactamase (ESBL)-producing E. coli, notably the O25b-ST131 clone, adds complexity to UTI management. The prevalence of ESBL-producing E. coli varies globally due to factors including regional antimicrobial usage practices.

 The goal of this study was to identify and molecularly characterize ESBL-producing E. coli isolates to identify the pandemic O25b-ST131 clone related to UTIs in one healthcare institution in Mexico.

 Bacterial species identification and antibiotic susceptibility tests were performed using the VITEK 2. The ESBL genes were identified using polymerase chain reaction (PCR). The E. coli genotyping was carried out by the phylogenetic group analysis and the O25b-ST131 identification.

 A total of 86 unique E. coli isolates were confirmed as ESBL, and 75% were obtained from UTIs. The most prevalent β-lactamase genes were blaCTX-M (66%), blaTEM (8.1%), blaCTX-M/SHV (5.8%), blaCTX-M/TEM (4.6%), and blaSHV (2.3%). The B2 phylogroup was most prominent (54.4%), with 46.5% identified as a globally pandemic O25b-ST131 clone. No evident relationship was observed using random amplified polymorphic DNA (RAPD) between nosocomial and community-acquired infections in ESBL-producing E. coli isolates.

 The obtained findings highlight the significance of monitoring molecular epidemiology in antibiotic resistance profiles of the O25b-ST131 E. coli clone.