Multiple antibiotic resistances among Shiga toxin producing Escherichia coli O157 in feces of dairy cattle farms in Eastern Cape of South Africa

Background: Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a well-recognized cause of bloody diarrhea and hemolytic-uremic syndrome (HUS). The ability of STEC strains to cause human disease is due to the production of Shiga toxins. The objectives of this study were to determinate the prevalence, serotypes, antibiotic susceptibility patterns and the genetic capability for Shiga toxin production in Escherichia coli (STEC) strains isolated from dairy cattle farms in two rural communities in the Eastern Cape Province of South Africa. Methods: Fecal samples were collected between March and May 2014, from individual cattle (n = 400) in two commercial dairy farms having 800 and 120 cattle each. Three hundred presumptive isolates obtained were subjected to polymerase chain reactions (PCR) for identification of O157 serogroup and Shiga toxin producing genes (stx1, stx2) on genomic DNA extracted by boiling method. Susceptibility of the isolates to 17 antibiotics was carried out in vitro by the standardized agar disc-diffusion method. Results: Based on direct PCR detection, 95 (31.7 %) isolates were identified as O157 serogroup. The genetic repertoire for Shiga toxin production was present in 84 (88.42 %) isolates distributed as stx1 (37), stx2 (38) and stx1/2 (9) respectively while 11 of the isolates did not harbor Shiga toxin producing genes. Multiple antibiotic resistances were observed among the isolates and genetic profiling of resistance genes identified bla(ampC) 90 %, bla(CMY) 70 %, bla(CTX-M) 65 %, bla(TEM) 27 % and tetA 70 % and strA 80 % genes among the antimicrobial resistance determinants examined. Conclusion: We conclude that dairy cattle farms in the Eastern Cape Province are potential reservoirs of antibiotic resistance determinants in the province.