Membrane filter procedure for enumeration of Candida albicans in natural waters

Abstract

A membrane filter procedure is described for the enumeration of Candida albicans in natural waters. Several hundred milliliters of sample can be examined by filtration through 1.2-μm membranes. Selectivity is achieved by the use of a defined (yeast-nitrogen base plus maltose) agar medium, inclusion of the antimicrobial agents chloramphenicol and cycloheximide, and incubation at 37°C. C. albicans colonies are differentiated primairly through color by use of a bismuth salt indicator system. Average recovery of various strains of C. albicans stressed in seawater at 4°C was 82%, compared with those of spread plate controls on a noninhibitory medium. With river water and raw sewage, 90% of typical C. albicans colonies were confirmed as such in a simplified germ tube test. Atypical colonies verified as C. albicans were infrequent (3%). C. tropicalis and Torulopsis candida were the most common false-positive colonies.