Phenotypic population characteristics of the enterococci in wastewater and animal faeces: implications for the new European directive on the quality of bathing waters

Faecal pollution of recreational bathing waters may derive from point sources of various wastewaters or from more diffuse sources such as run-off of agricultural wastes. The paper describes the application of population similarity studies to the enterococcal flora of various animal faeces and municipal wastewaters as a means of distinguishing human from animal faecal material. A simplified phenotypic testing technique (PhenePlate, PhP) was used to study the fermentation kinetics of eleven carbohydrates by all bacterial isolates. Enterococcal isolates (1,766) from six sources were investigated. Enterococcal population diversity (measured as Simpson's Diversity Index) in wastewater samples was high (mean D-i = 0.95) compared with those of non-human faeces. The mean diversity of isolates in seabird faeces was 0.72, in sheep and donkey faeces 0.44, in dog faeces 0.42 and in cattle faeces 0.32. Analysis of population similarity coefficients demonstrated that faeces from sheep and cattle showed the greatest similarity (S-P = 0.72). Sheep and cattle faeces demonstrated a low similarity to municipal wastewater samples. This would suggest that population similarity studies might be a useful tool for distinguishing the relative contributions of municipal wastewater and agricultural run-off to bathing water pollution. The PhP procedure identified a specific PhP type that appears to have high specificity to non-human faeces. It may, therefore, represent an important tool in source tracking. Additional phenotypic and genotypic analysis of PhP types that demonstrate a high degree of source specificity is required. The benefits and limitations of the use of population similarity studies to distinguish pollution sources are discussed in comparison with other source tracking approaches and the implications of these developments for future European Union legislation on the quality of bathing waters are discussed.