Quantitative PCR (QPCR) technology, incorporating fluorigenic 5 nuclease (TaqMan) chemistry, was utilized for the specific detection and quantification of six pathogenic species of Candida (C. albicans, C. tropicalis, C. krusei, C. parapsilosis, C. glabrata and C. lusitaniae) in water. Known numbers of target cells were added to distilled and tap water samples, filtered, and disrupted directly on the membranes for recovery of DNA for QPCR analysis. The assay's sensitivities were between one and three cells per filter. The accuracy of the cell estimates was between 50 and 200% of their true value (95% confidence level). In similar tests with surface water samples, the presence of PCR inhibitory compounds necessitated further purification and/or dilution of the DNA extracts, with resultant reductions in sensitivity but generally not in quantitative accuracy. Analyses of a series of freshwater samples collected from a recreational beach showed positive correlations between the QPCR results and colony counts of the corresponding target species. Positive correlations were also seen between the cell quantities of the target Candida species detected in these analyses and colony counts of Enterococcus organisms. With a combined sample processing and analysis time of less than 4 h, this method shows great promise as a tool for rapidly assessing potential exposures to waterborne pathogenic Candida species from drinking and recreational waters and may have applications in the detection of fecal pollution.Yeasts are a significant component of the microbiota of most natural aquatic ecosystems (17, 33) and can also occur in drinking water distribution systems as a result of their ability to survive treatment practices and become incorporated into biofilms (6,12,22,30,31). The majority of these organisms have no known human health effect. However, a small number of species, primarily within the anamorphic genus Candida, are important opportunistic pathogens (23).The importance of pathogenic Candida as agents of nosocomial infections has led to the development of a number of modern molecular diagnostic methods to facilitate their detection and identification in clinical samples. Methods based on the PCR and DNA hybridization probes have received particular attention (9,25,26,32,39). The more recent advent of fluorescent probe-based PCR technology (21) has led to the development of homogeneous methods for detecting these organisms that require relatively short periods of time to perform (16,28).Quantitative PCR (QPCR) has been demonstrated to be useful for quantitative analysis of microorganisms in environmental samples (29,34,35,36), but, to our knowledge, this approach has not been used in the analysis of yeasts in water. Analyses for pathogenic yeasts in drinking or recreational water systems have the potential to expedite the identification of possible health hazards resulting either directly from the presence of these organisms or, as their presence might indicate, indirectly from other waterborne pathogens.The first object...