Investigating the occurrence of E. coli O157:H7 in the final effluents of two wastewater treatment plants.

Abstract

AIM: The final effluent of two wastewater plants located in the Eastern Cape of South Africa were tested for the presence of Enterohaemorrhagic Escherichia coli O157:H7 (E. coli O157:H7) isolates, and characteristics of the isolates obtained were determined. METHODS AND RESULTS: A total of 23 wastewater samples were collected from the treatment plants at the final effluent point after the disinfectant stages of wastewater processing. Altogether, 540 presumptive E. coli isolates were obtained by colony counting on the E. coli O157:H7 chromogenic agar base supplemented with cefixime tellurite and were sub-cultured onto sorbitol-MacConkey agar and tested for agglutination using the Prolex E. coli O157 latex test reagent kit. The results showed that the 149 suspected colonies from SMAC agar were all negative for the antisera. CONCLUSION: None of the isolates agglutinated with antisera against E. coli O157. Thus no presence of the bacteria can be confirmed from the treated effluents SIGNIFICANCE AND IMPACT OF STUDY: The likelihood of the receiving water body and the environment being contaminated with E. coli O157:H7 is therefore minimal.