Abstract

Objective: To investigate the occurrence and antibiotics susceptibility of Escherichia coli (E. coli) O157:H7 isolates from raw milk, cattle udder, milking machines and worker’s hand swabs from three selected commercial dairy farms in the Amathole District Municipality, Eastern Cape Province, South Africa. Methods: Raw milk samples were collected from bulk storage tanks and swab samples were collected from milking machines, cattle udders and worker’s hands fortnightly over a sixmonth sampling regime between June and November 2014. A standard culture-based method was used for the enumeration and isolation of E. coli O157:H7, presumptive identification using sorbitol MacConkey agar (supplemented with cefixime (50 µg/L) and potassium tellurite (25 mg/L). A serological confirmation of the presumptive E. coli O157:H7 isolates was conducted using the O157 latex agglutination test kit. Results: A total of 252 E. coli O157:H7 isolates were further subjected to PCR amplification of rfbEO157 and flCH7 genes of which 27(11%) of the isolates were confirmed positive E. coli O157:H7. The percentage antibiotic resistance of the 27 E. coli O157:H7 isolates from the dairy farms revealed penicillin [23 (85%)], tetracycline [22 (81%)], erythromycin [19 (70%)], streptomycin [14 (52%)] and chloramphenicol [12 (45%)]. The highest resistances were penicillin [23 (85%)] and tetracycline [22 (81%)]. Conclusions: These findings revealed that the dairy farms are potential reservoirs of E. coli O157:H7 serotype, and harbor antibiotic-resistant determinants, a concern to public and environmental health.

Authors and Affiliations