Incidence and antimicrobial susceptibility of Escherichia coli O157:H7 isolates recovered from dairy farms in Amathole District Municipality, Eastern Cape, South Africa

Objective: To assess the incidence of Escherichia coli (E. coli) O157:H7 in water and cattle rectal samples from three commercial dairy farms in Amathole District Municipalities in the Eastern Cape Province of South Africa. Methods: Samples were collected bimonthly from cattle rectum and dairy water sources including irrigation water, drinking water troughs and wastewater between June and November 2014. Standard culture-based methods were applied for the microbial analyses, the disc diffusion method was employed for the antibiotic susceptibility test and PCR approach was utilized for identification of the isolates. Results: A total of 252 presumptive E. coli O157:H7 were isolated and subjected to molecular confirmation by PCR. About 18.7% (47/252) of these were confirmed as E. coli O157:H7. The antimicrobial susceptibility profile of these confirmed isolates revealed high-level resistance against penicillin G (81%), tetracycline (43%), oxytetracycline (62%), erythromycin (68%), sulphamethoxazole (57%), chloramphenicol (55%), doxycycline (51%) and trimethoprimsulphamethoxazole (45%). Conclusions: This is the first report of multi-drug resistance E. coli O157:H7 in commercial dairy farms in the province and suggests the possibility of same in other provinces of the country, and this is the subject of the intensive investigation in our group.