Some observations on the ecology of Candida albicans, a potential mammalian pathogen
- Department of Microbiology, University of Otago
(1) Candida albicans has been shown to be an inhabitant of the alimentary tract of man and 7 other mammals in New Zealand.
(2) Although the yeast was present in the mouths of up to 40% human subjects, it was not isolated from the general skin surface of 278 children aged 2 to 13 years.
(3) Skin carriage of Candida albicans was demonstrated in only 1.4% of 72 students aged 17 to 22 years while the yeast was recovered from 27.0% of geriatic subjects aged more than 60 years. The difference in incidence is statistically significant.
(4) The possible factors leading to the disappearance of C. albicans from young healthy skin are discussed and it is suggested that desiccation is of major importance in the self-sterilising process. Experiments on the effect of desiccation on the viability of C. albicans in vitro were carried out. The average number of viable cells of the yeast exposed to desiccation fell from 105 to 102/ml in 3 hours, regardless of whether the environment temperature was 37¡C or 27¡C. The number of viable cells in control preparations, maintained in a saturated environment, remained more or less constant during the same period. The difference in number of viable cells after 3 hours in the presence or absence of desiccation was statistically significant (p Rhodotorula species isolated from the soil.
(5) The distribution of spontaneously acquired cutaneous lesions of candidiasis in man is noted. Since these occur in areas of skin which are normally maintained in conditions of high humidity, this distribution supports the hypothesis that Candida albicans requires moist conditions for its survival.
(6) The reasons for the survival of C. albicans on the skin of geriatric subjects are unknown and require further investigation. It is unlikely that diminution of sebaceous secretion accounts for the ability of the yeast to establish itself as a member of the normal cutaneous flora of elderly subjects.