Isolation, identi cation, and molecular characterization of E. coli isolates
The samples collected were analyzed by standard mem- brane ltration technique according to (APHA/AWWA/ WEF 1998). Three hundred presumptive E. coli isolates were recovered on E. coli-Coliforms Chromogenic medium (Laboratorios CONDA, South Africa) incubated at 37°C for 24 h. About 5–7 randomly selected distinct blue colonies were isolated per plate and subjected to pre- liminary identi cation by Gram staining and oxidase testing. Further identi cation of the selected colonies was done by polymerase chain reaction (PCR). Bacterial DNA was extracted by boiling method as described by Queipo- Ortuno et al. (2008) with modi cations. The isolates were con rmed using housekeeping uidA [β-D glucuronidase] gene as described by Janezic et al. (2013). Polymerase chain reaction (PCR)-con rmed E. coli isolates were then stored in 20% glycerol and frozen at −80°C until further analysis.