Genotyping of F-RNA coliphages isolated from wastewater and river water samples

Abstract

Faecal contamination of water sources can only be managed if the sources of pollution are identified and thus tools to distinguish between human and animal faecal sources are needed. Male-specific F-RNA coliphages have been classified into four sero-groups and evidence has been presented that two of these sero-groups are specific for human excreta and the other two for animal excreta. The sero-groups are readily detectable as genotypes with the application of molecular techniques, notable hybridisation tests using gene probes specific for each genotype. A standard ISO method was used for the detection of F-RNA coliphages. Wastewater containing predominantly animal excreta was collected from cattle, pig and chicken feedlots. Wastewater containing predominantly human excreta was collected from hospitals. The F-RNA genotyping study was qualitative and focussed on determining which groups of F-RNA phages were present in different wastewater and environmental samples. The results were in agreement with earlier reports on the specificity of F-RNA phage Genotypes 1 and 4 for animal wastes, and Genotypes 2 and 3 for human excreta. Besides being detected in human wastewater, F-RNA Group 3 was detected in both chicken and pig wastewater indicating that this Group was not specific to humans. The results showed that F-RNA phage Group 2 was the only group detected in seven of the twenty-six positive samples from the Dorpspruit, Slangspruit and uMsunduze Rivers, suggesting human faecal input. All other river water samples contained mixtures of F-RNA phage groups suggesting that the faecal input could not exclusively be ascribed to humans or animal sources alone. This suggested that both human and animal sources were responsible for contamination of receiving water at these sampling sites. The research proved that the genotyping of F-RNA phages was feasible in practice and could be used to assist in identifying the source of faecal pollution.