Molecular characterization of Shigatoxigenic Escherichia coli (STEC) in sheep and goat in Krishna district of Andhra Pradesh

Shiga toxin-producing Escherichia coli (STEC) strains represent an emerging threat in foodborne bacterial pathogens. The present study was designed to determine prevalence of STEC, antibiogram profile, ESBLs and genetic diversity. Among the 468 samples analyzed, 172 (36.75%) were confirmed to be E. coli by species specific PCR. Out of the 172 confirmed E. coli isolates, 42 (24.41% ) isolates carried either stx1, stx2 or both indicating them to be STEC. Along with shiga toxins, virulence genes eaeA and hlyA genes were also present in some of the isolates. The antibiogram profile of STEC isolates revealed highest resistance against ampicillin (90.47%) followed by tetracycline (80.95%), amoxicillin-clavulanic acid (76.19%), co-trimoxazole (71.42%), ceftriaxone (69.04%), ciprofloxacin (54.76%), chloramphenicol (21.42%) and amikacin (14.28%). Extended spectrum β-Lactamase (ESBL) genes were detected in 10 isolates, with blaTEM in seven isolates and blaCTX-M-9 in three isolates. Both ERIC and REP-PCR genotyping methods differentiated STEC into different strains and are considered to be highly suitable genotyping methods and can be effectively utilized for epidemiological investigation of isolates.