Phenotypic variations of enterococci in surface waters: analysis of biochemical fingerprinting data from...

The aim of this study was to identify the prevalence of environmentally adapted enterococci strains by analysing biochemical fingerprinting (BF) data of 3952 enterococci isolates collected over 5 years from the six catchments in Southeast Queensland, Australia.

A BF method was used to type 3952 enterococci isolates from six catchments. The environmental isolates were compared with a large existing BF library comprised of 5803 enterococci isolates from 10 host groups. Environmental isolates belonged to 801 biochemical phenotypes (BPTs), of which, an average of 29.2% was specific to each catchment. When compared with the BF library, an average of 79.5% BPTs from each catchment was identical to those in the library (i.e. host-origin BPTs). The remaining 20.5% was regarded as non-host origin BPTs, as they were not in the library and constituted only 5.3% of the total isolates tested for each catchment.

Our data suggest that less than 5% of studied environmental strains was not identical to those in the library and seemed to be of environmental origin. From a microbial source tracking context, such low level of environmentally adapted strains can have a minimal impact on the performance of the library-based methods if a large number of isolates were tested from both the host groups and environmental waters.

These data shed light on the importance of the size and representativeness of library-based source-tracking methods and their implications for the identification of faecal pollution in environmental waters.