EMERGENCE OF CARBAPENEM RESISTANCE AMONG EXTENDED SPECTRUM BETA-LACTAMASE ISOLATE OF Escherichia coli FROM CLINICAL SPECIMENS IN A TERTIARY HOSPITAL, NIGERIA

Extended-spectrum β-lactamases (ESβLs) are a rapidly evolving group of β-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. In this study, the aim was to determine the susceptibility of ESβL producing clinical isolates of Escherichia coli across various antimicrobial agents according to the Clinical Laboratory Standard Institute (CLSI) new breakpoints. Sixty five clinical isolates of Escherichia coli were collected from a Tertiary Hospital in Nigeria of which forty six ESβL-producing isolates emerged. Presence of ESβL was determined by double- disk synergy test, DNA extraction and amplification of ESβL genes- blaSHV, blaTEM, blaCTX-M by Polymerase Chain Reaction. Susceptibility of the ESβL-producing isolates was determined by the CLSI agar diffusion method. Utilizing the CLSI new breakpoints, 76.09%, 73.91%, 73.91% and 63.04% were resistant to Cefotaxime, Ceftazidime, Aztreonam and Cefepime respectively. While, 19.6%, 15.2%, 21.7% and 40% were susceptible to Cefotaxime, Ceftazidime, Aztreonam and Cefepime respectively. Furthermore, though a significant number of ESβL-producing isolates were susceptible to carbapenem; ESβL isolates that harboured the blaSHV, blaTEM, blaCTX-M genes showed resistance to carbapenem. Thus, carbapenem-resistant ESβL-producing isolates emerged from this study. In conclusion, Nigeria is a developing country affected by the spread of bacterial strains harbouring ESβL and with the emergence of carbapenem resistance; it is certain to create significant therapeutic problems as carbapenem is the drug of choice for serious infections caused by ESβL-producing Escherichia coli