In vitro survival of human pathogenic fungi in Hawaiian beach sand

In vitro studies utilizing 4 pathogenic fungi, Trichosporon cutaneum, Candida albicans, Microsporum gypseum and Trichophyton mentagrophytes, all known from Hawaiian beaches, indicate that they survive in the fluctuating beach habitat where they can serve as potential sources of infection for significant periods of time. Survival was measured by testing the viability of propagules at intervals for 6 months. All species survived 6 months under 1 or more experimental conditions. Survival patterns showed both increases and decreases depending upon the given parameters designed to simulate various beach conditions. Propagules inoculated on hair and horn (keratinized inoculum) did not remain viable longer than propagules from pure culture suspensions (non-keratinized). Microbial antagonism was not a major factor in survival. All species survived at least 1 month in non-sterile sand inoculated with keratinized propagules. This condition approximated the natural sand habitat. Alternate wetting and drying of sand caused an overall decrease in survival time except for M. gypseum (non-keratinized inoculum) at 37 degrees C in sterile sand and T. mentagrophytes (keratinized inoculum) at 37 degrees C in non-sterile sand. Temperature was important: increasing temperature resulted in a general decrease in survival time; 45 degrees C was definitely inhibitory, with the exception of T. cutaneum which survived that level for 6 months (keratinized inoculum). Salinity did not influence survival.