Genotypic Profiling of Virulence and Antibiotic Resistance Genes of Escherichia coli Isolates Derived From Bovine Milk in the Dr. Kenneth Kaunda District, South Africa.

The growing threat of antimicrobial resistance (AMR) among foodborne pathogens poses a significant public health risk in South Africa, largely driven by excessive antibiotic use in dairy farming practices. This study investigated the virulence and AMR profiles of Escherichia coli isolated from bovine quarter milk samples in the Dr. Kenneth Kaunda District, North West Province, South Africa. Sixty-five E. coli isolates were confirmed using the automated identification Sensititre ARIS 2X ID/AST System and PCR targeting the uidA gene. Serogrouping revealed a predominance of non-O157 strains, with O128 (50.8%) as the dominant serogroup, followed by O145 (9.2%), whereas 40% of isolates were nontypable, highlighting serotype diversity. The fliC gene encoding flagellin was the most prevalent virulence marker (62.5%), whereas stx1 was detected in 9.2% of isolates, and stx2 was absent. Phenotypic testing demonstrated high resistance to amoxicillin/clavulanic acid and cephalothin (58.9% each), tetracycline (37.8%), and trimethoprim-sulfamethoxazole (3.3%). However, no isolates exhibited phenotypic multidrug resistance (MDR), despite 98.5% harboring one or more resistance genes: ermB (92.3%), vanB (90.8%), tetM (56.9%), and ampC (10.8%). The high prevalence of ermB and vanB may indicate coselection of resistance determinants and suggests their potential association with mobile genetic elements that facilitate dissemination among bacterial populations. These findings indicate that E. coli from bovine milk in the region serve as silent reservoirs for virulence and resistance genes. These findings are vital for managing E. coli isolates in dairy farming and taking proactive measures to limit AMR in animals.