Leachate emanating from a municipal solid waste dumpsite is a hotspot of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli harboring CTX-M β-lactamase

Abstract

Background: Antibiotic resistance constitutes a key challenge to global public health and is on an alarming rise. In Nigeria, this quagmire has been extensively studied in clinical settings but not in the environmental sector, particularly in landfill leachates. Aim: We aimed to assess the susceptibility profile of Escherichia coli from leachate obtained from Lapite dumpsite, to determine the potential of dumpsite leachate as a source of ESBL-producing Escherichia coli. Methods: Cefotaxime-resistant Escherichia coli was isolated on cefotaxime-enriched chromogenic medium and identified via PCR using uidA gene. The confirmed isolates from the pool were assessed for susceptibility to antibiotics using the disc-diffusion method, while the phenotypic detection of ESBL production was done using the double disc synergy test. Detection of ESBL genes was done using primer-specific PCR. Results: Twenty-three ESBL-producing E. coli were obtained, and they showed 100% resistance to cefotaxime and cefpodoxime, and 60.87% resisting imipenem (a carbapenem). However, none of the isolates was resistant to amoxicillin-clavulanate. The resistance to the other antibiotics tested was: gentamicin (4.35%), ciprofloxacin (17.39%), nalidixic acid (26.09%), ceftazidime (26.09%) and chloramphenicol (30.43%). Seventy-four percent of the isolates had multiple antibiotic resistance index (MARI) greater than 0.3, with 30.4% (n=7/23) exhibiting multidrug resistance phenotypes. All the isolates carried blaCTX-M, but none harboured blaSHV or blaTEM. Conclusion: Landfill leachates could contribute to the evolution of antibiotic-resistant ESBL-producing E. coli harboring ESBL genes. There should effective precautionary methods in place to prevent dumpsite leachates from flowing into adjoining environment to safeguard public and environmental health.