Detection of Enterococci in Freshwater and Seawater (16S and 23S rRNA Enterococcus Oligonucleotide Probes)

Enteric bacteria, such as members of the enterococci and fecal coliform groups, are widely used as sanitary indicators of water quality in marine and freshwater systems. However, recent studies investigating the survival characteristics of these enteric bacteria in the laboratory (1 –3 ,) and in situ (4 ,5 ) have indicated that traditional enumerative techniques, based on selective culture, do not detect all viable bacteria present. It is now widely acknowledged that microorganisms become injured as a result of exposure to stressful environments (6 ) and that this injury may impede growth under the stringent conditions imposed by selective culture. The term viable but nonculturable (VNC) has been used to describe those organisms that, on exposure to an adverse environment (7 –9 ,) can no longer be cultured but have maintained some metabolic capability, as evidence by vital staining (10 –12 ,) and in some cases have retained their virulence (7 ,13 ,14 ). The VNC state has been demonstrated for a number of bacterial species including E. coli (9 ,15 ), and enterococci (16 ), and occurs in response to a range of environmental stresses such as sunlight exposure, salinity, nutrient limitation, and pH and temperature fluctuations.