Beyond Susceptibility: Antimicrobial Resistance Patterns and Molecular Characterisation of ESBL-Producing E. coli and Circulating Carbapenem-resistance Genes in Clinical Isolates

Antimicrobial resistance among clinical Escherichia coli isolates restricts treatment options and highlights the need for local susceptibility and molecular surveillance. This study investigated antimicrobial resistance patterns, extended-spectrum beta-lactamase (ESBL) production and selected carbapenem-resistance genes among clinical isolates obtained at Abubakar Tafawa Balewa University Teaching Hospital, Bauchi. Of 317 clinical specimens processed, 170 E. coli isolates were recovered and evaluated using the Kirby–Bauer disc diffusion method. Phenotypic ESBL production was assessed using the double-disc synergy test, suspected carbapenemase production was examined using the modified Hodge test, and OXA-48 and KPC genes were investigated by polymerase chain reaction. Of the 170 isolates, 93 (54.7%) exhibited multidrug resistance, while 24 (14.1% of all isolates; 25.8% of multidrug-resistant isolates) were ESBL producers. Among the ESBL-producing isolates, 13 (54.2%) demonstrated resistance or reduced susceptibility on carbapenem screening, and 10 of these (76.9%) were positive in subsequent modified Hodge testing. Thus, the 10 isolates represented 5.9% of all E. coli isolates. Molecular analysis identified OXA-48 alone in two isolates (20%) and co-detection of OXA-48 and KPC in one isolate (10%). Urine accounted for 106 (62.3%) of all E. coli isolates and seven (70.0%) of the carbapenem-resistant isolates. These findings document multidrug resistance, ESBL production and the investigated carbapenem-resistance determinants at the study hospital. Continued laboratory surveillance and antimicrobial stewardship are warranted.