IDENTIFICATION OF SOURCES OF FAECAL SOURCE ISOLATES IN NINGI CREEK, AUSTRALIA

This study was undertaken to investigate the feasibility of using antibiotic resistance patterns (ARP) for source tracking faecal contamination in surface waters, and linking faecal contamination to on-site wastewater treatment systems (OWTS). ARP's were established for a library of 1005 known E. coli source isolates obtained from human, domesticated animals, livestock and wild sources. Eight commonly used antibiotics at four different concentrations were used to obtain ARP's for the E. coli isolates. Discriminant Analysis (DA) was used to differentiate between the ARP of sources isolates, and identify the predictive ability of the library for classifying between isolates collected from human, wastewater treatment plant and on-site system sources. The source library was used to identify sources of faecal contamination in investigated surface waters and determine the significance of OWTS as a major contributor to faecal contamination. The developed ARP library was found to be adequate for discriminating human from non-human isolates, and was used to classify 144 enumerated E. coli isolates collected from monitored surface water locations. The resulting ARP DA indicated that a majority of the faecal contamination in more rural areas of the study catchment was non-human. However, the percentage of human isolates increased significantly in urbanised areas using on-site systems for wastewater treatment.