Ecology and epidemiology of Candida species.

Exogenous and endogenous sources of pathogenic Candida species and the likely routes of their intra- and inter-human transmission are reviewed. Study of C. albicans strain types from clinical isolates of the fungus has shown that, for each person who harbours C. albicans, the strain type or types at different anatomical sites and at different times is likely to be the same, although exceptions to this rule are not uncommon. Moreover, the population of strain types associated with infection is statistically the same as that isolated in the absence of infection, which emphasises the importance of host debilitation in the aetiology of Candida infections. There are variations among C. albicans strain types in different geographical areas, and differences in phenotypic properties such as serotype and resistance to 5-fluorocytosine correlate also with other phenotypic properties of the fungi.