Abstract

Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a formidable human pathogen causing food-borne diseases worldwide. The present study investigates virulence genes and determines the antimicrobial characteristics of STEC O157:H7 isolates from faecal and effluent samples at Zaria abattoir in Zaria. PCR assays were used to detect the virulence genes of STEC O157:H7 isolates. The isolates that produced stx genes were subjected to antibiotic susceptibility testing using Kirby Bauer disc diffusion technique. Out of the 13 STEC O157:H7 isolates evaluated, E. coli 16SrRNA gene was detected in 12 isolates (92.3%) and the distribution of the virulence genes showed that of the 12 E. coli 16SrRNA gene positive isolates, 10 (83.3%) had stx₁ gene, 2 (16.7%) produced stx₂ gene, 2 (16.7%) harbored both stx₁ and stx₂ genes, and 2 (16.7%) lacked stx genes. Similarly, 8.3% had hlyA gene, 58.3% were positive for fliC gene and none produced eaeA gene. The ten isolates that produced stx genes were highly susceptible to Imipenem 100%, Ciprofloxacin 100%, and Ofloxacin 100% while strong resistance was observed against Cefepime 90.0%, Streptomycin 70.0% and Ampicillin 70.0% and Tetracycline 60.0%. Also, 80.0% of the ten stx genes positive isolates exhibited Multiple Antibiotic Resistance (MAR), with the Multiple Antibiotic Resistance Index (MARI) ranging from 0.083 to 0.67. 60.0% exhibited Multiple Drug Resistance (MDR) traits. These high MAR and MDR values suggest that there may be abuse of antibiotics in the study area. Thus, good hygienic practices should be adopted in abattoirs to prevent the transmission of STEC O157:H7 pathogens responsible for many foodborne diseases in humans.

Key words: Abattoir, effluent, virulence genes, antibiotic susceptibility, Shiga toxin-producing Escherichia coli (STEC).