Environmental growth of the faecal indicator Enterococcus moraviensis

Soil passage through sand dunes has previously been shown to remove enteric micro-organisms very effectively, and hence is used for the production of drinking water. However, enterococci have occasionally been isolated from abstracted water (after dune passage) in one of the dune infiltration areas in the Netherlands. Enterococcus moraviensis was the most frequently isolated species. Until now, no faecal sources of this species have been reported and the potential for growth under certain environmental conditions was reported for other Enterococcus species. The aim of this study was to determine the ability of E. moraviensis to grow in habitats present in the dune passage process (dune vegetation, sediment from abstraction wells, biofilm developed using abstracted water and soil). Different concentrations of boiled and filtered (0.45 μm) plant extracts obtained from dune vegetation supported growth (up to 6 log), with maximum concentrations after 4 to 6 days at 15 °C. Although E. moraviensis was shown to be able to attach to the biofilm, no growth was observed in biofilm or in sediment and soil. These observations confound the use of E. moraviensis as a faecal indicator.