Detection and source identification of faecal pollution in non-sewered catchment by means of host-specific molecular markers.

Multiple host-specific molecular markers were used to detect the sources of faecal pollution in a mixed land use non-sewered catchment in Southeast Queensland, Australia. These markers included human-specific Bacteroides (HF183 and HF134), cattle-specific Bacteroides (CF128), dog-specific Bacteroides (BacCan) and human-specific enterococci surface protein (esp) markers. The sensitivity and specificity of these markers were determined by testing 197 faecal samples from 13 host groups. The overall sensitivity and specificity of these markers was high (sensitivity>/=85% and specificity>/=93%) indicating their suitability for detecting the sources of faecal pollution. Of the 16 samples collected from the study area, 14 (87%) were positive for at least one of the molecular marker tested. Amongst all the markers, cattle-specific CF128 was more prevalent than others, followed by human-specific HF183 which was consistently detected in samples collected from sites within close proximity to urban development. Significant correlations were found between E. coli and enterococci concentrations with the positive/negative results of human-specific Bacteroides HF183 (p<0.001, p<0.0001) and HF134 (p<0.001, p<0.004) markers. No correlations were found between faecal indicators (E. coli or enterococci) with the CF128 or BacCan markers. A significant correlation was also found between enterococci concentrations and the presence/absence of the esp marker (p<0.02). Based on the results, it appears that the host-specific markers such as HF183 and esp are a sensitive measure of sources of human faecal pollution in surface waters in Southeast Queensland, Australia.