PHENOTYPIC CHARACTERIZATION AND ANTIMICROBIAL RESISTANCE OF PRESUMPTIVE ESCHERICHIA COLI O157:H7 IN ABATTOIR EFFLUENTS IN JOS, NIGERIA

Abstract

Discharge of untreated abattoir wastewater into urban ecosystems facilitates the dissemination of Shiga toxin-producing Escherichia coli (STEC), posing a severe zoonotic risk. This study characterized presumptive E. coli O157:H7 isolates from abattoir effluents in Jos, Nigeria, assessing their environmental distribution and antimicrobial resistance profiles. A total of 120 samples (wastewater and process water) were collected from slaughterhouses and associated drainage systems. Physicochemical parameters, including Biological Oxygen Demand (BOD), turbidity, and conductivity, were analyzed using standard titrimetric and electrometric methods. E. coli was isolated via enrichment and selective plating on Sorbitol MacConkey (SMAC) agar. Presumptive O157:H7 strains, identified as Non-Sorbitol Fermenters (NSF), were characterized using biochemical methods. Antibiotic susceptibility testing (AST) was conducted using the Kirby-Bauer disk diffusion method, and the results were interpreted using CLSI guidelines.  Physicochemical analysis indicated that temperature, pH, and conductivity remained within regulatory limits; however, BOD and turbidity levels showed marked fluctuations. Drainage water demonstrated the highest mean microbial density (1.18×10¹² CFU/ml), though no statistically significant correlation (p>0.05) was established between bacterial load and water source.  Of the 115 E. coli isolates, 13 (11.3%) were identified as NSF, with a notable cluster identified in the Vom Pig slaughterhouse. Resistance was most prevalent against tetracycline (76.9%), cefixime (69.2%), and ampicillin (61.5%). Conversely, high susceptibility was maintained for colistin sulphate (69.2%), amoxicillin (69.2%), and imipenem (61.5%). There is an urgent need for stricter enforcement of Hazard Analysis and Critical Control Points in Jos abattoirs to mitigate the risk of foodborne outbreaks.