Assessment of well water as a reservoir for extended-spectrum β-lactamases (ESBL) and carbapenem resistant Enterobacteriaceae from Iwo, Osun state, Nigeria

BACKGROUND AND OBJECTIVES: Unsafe water supplies are of public health concern, especially in developing countries. This article aims to investigate the microbiological quality of water from eight Wells in Iwo and to explore for the extended-spectrum β-lactamase (ESBL) and carbapenemase genes contained in isolated enteric bacteria from in the water samples. MATERIALS AND METHODS: Bacterial isolation and identification were done using standard conventional methods. Antibiotic susceptibility testing was conducted using the Kirby–Bauer method. Ten phenotypically carbapenem-resistant isolates were further subjected to genotypic analysis (PCR amplification) for the detection of ESBL and carbapenemase gene. RESULTS: A total of 148 Enterobacteriaceae isolates belonging to seven (7) genera were isolated and identified which included E. coli, Enterobacter spp., Klebsiella spp., Salmonella, Citrobacter sp, Proteus, and Shigella. Results showed that 55% of isolates were resistant to tetracycline, 28% to cefepime, the least resistance was shown in moxifloxacin and gentamicin which had 6% and 9%, respectively, of the total isolates. For the two carbapenems used, results showed meropenem and imipenem had resistant values of 14% each, respectively. Two isolates carried the bla(CTX-M) gene while the carbapenemase gene (bla(KPC), bla(NDM), and bla(OXA)) was not detected in all the ten isolates. CONCLUSION: There was also negative chromosomal detection of carbapenemase in MDR isolates from well waters in Iwo town. Consequently, resistance to carbapenem antibiotics in these isolates may not be mediated by carbapenemase but by the production of extended-spectrum β-lactamases and through other mechanisms of resistance.