Virulence Traits and Drug Resistance of STEC Isolated from Layer Poultry and Rattus Species

Shiga toxin-producing Escherichia coli (STEC) has emerged globally as a critical enteric foodborne zoonotic pathogen with significant public health implications. This study aimed to isolate and characterize STEC strains from Rattus spp. and layer chickens, specifically evaluating their antimicrobial resistance (AMR) profiles and the prevalence of extended-spectrum β-lactamase (ESBL)-producing isolates. A total of 274 fecal samples were collected from Rattus spp. (n = 154) and layer chickens (n = 120). Isolates were characterized using standard microbiological techniques, PCR amplification of specific genes (including uidA and stx), and antimicrobial susceptibility testing via the disk diffusion method. Results: Of the 248 presumptive E. coli isolates, 237 (95.5%) were confirmed via uidA gene amplification. Fifty-eight isolates were confirmed as STEC, including key O-serogroups (O103, O111, O26, and O157). Resistance was most prevalent against colistin (39.6%) and streptomycin (20.6%), with 8.6% of isolates exhibiting multidrug resistance (MDR). Additionally, 19 isolates showed ESBL-producing phenotypes, and resistance genes for colistin, phenicols, aminoglycosides, and carbapenems were detected. The presence of STEC and MDR strains in both rodents and poultry highlights a high pathogenic potential and a serious zoonotic risk to public health, necessitating enhanced surveillance.