Prevalence of Extended Spectrum Beta Lactamase Producing Escherichia coli from Selected Domestic Sewages at Iworoko-Ekiti, Ekiti State, Nigeria
F. A. Adewumi
*
Department of Medical Laboratory Science, Faculty of Basic Medical Science, Ekiti State University, Ado-Ekiti, Nigeria.
J. O. Ipinlaye
Department of Microbiology, Faculty of Science, Ekiti State University, Ado-Ekiti, Nigeria.
A. I. Airaodion
Department of Biochemistry, Faculty of Natural and Applied Sciences, Lead City University, Ibadan, Oyo State, Nigeria.
A. O. Oluyege
Department of Microbiology, Faculty of Science, Ekiti State University, Ado-Ekiti, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: The emergence of antimicrobial-resistant bacteria in environmental reservoirs poses a significant public health concern. This study investigated the prevalence, antimicrobial resistance patterns, and extended-spectrum beta-lactamase (ESBL) production among Escherichia coli isolated from untreated domestic sewage in Iworoko-Ekiti, Nigeria.
Research Methodology: A total of 45 sewage samples were collected from five locations and processed using standard microbiological techniques. Presumptive isolates were identified based on morphological and cultural characteristics on selective media and confirmed by 16S rRNA gene sequencing. Antibiotic susceptibility testing was performed using the disk diffusion method, and ESBL production was determined using the combination disk synergy test.
Results: Three enteric bacterial species were recovered, with E. coli representing the predominant isolate (23/45; 51.1%), followed by Klebsiella spp. (31.1%) and Enterobacter aerogenes (17.8%). Antibiotic susceptibility testing revealed high resistance among E. coli isolates to cefuroxime (95.6%), meropenem (78.2%), ciprofloxacin (78.2%), cefotaxime (73.9%), and ceftriaxone (69.5%), indicating widespread multidrug resistance. Moderate resistance was observed for amikacin, chloramphenicol, cotrimoxazole, and tetracycline (47.8% each), while gentamicin showed comparatively lower resistance (34.7%). ESBL production was confirmed in 13 of 23 E. coli isolates (56.5%). Synergy testing demonstrated enhanced inhibition with amoxicillin–clavulanate and cefotaxime in 39.1% of isolates and with ceftazidime in 21.7%. Site-specific analysis revealed the highest ESBL prevalence at the New Jersey hostel (80%).
Conclusion: These findings demonstrate that untreated domestic sewage serves as an important environmental reservoir of multidrug-resistant and ESBL-producing E. coli. The detection of resistance to critically important antibiotics highlights potential risks for environmental dissemination and public health exposure, emphasizing the need for improved sewage management, routine surveillance, and antimicrobial stewardship strategies.
Keywords: Extended-spectrum beta-lactamase (ESBL), Escherichia coli, antimicrobial resistance, domestic sewage contamination, multidrug-resistant bacteria, environmental reservoirs