Clonal population structure and genetic diversity of Candida albicans in AIDS patients from Abidjan (Côte d'Ivoire)

Abstract

We have investigated the genotype at 14 enzyme-encoding loci in 275 isolates of the pathogenic yeast Candida albicans sampled from 42 HIV-positive patients (all but one with AIDS) from Abidjan (Côte d'Ivoire). We separately analyzed the following variables: patient, residence, age, gender, T cell count, hospitalization (yes or no), drug treatment, date of sampling, multilocus genotype, and serotype. The most important factors contributing to the genetic variability of C. albicans are individual patient and gender. Our data manifest that the population size of the parasite is relatively small within each patient, although larger in women than in men, and that, at least for the patients involved in the study, the transmission rate of C. albicans between human adults is very low. Most important is the inference that the prevailing mode of reproduction of C. albicans in natural populations is clonal, so that sexual reproduction is extremely rare, if it occurs at all.

Fig. 1.

Comparison between F_st and F_st′ = −F_is/(1 − F_is) in males (■) and females (•). The bars mark 95% confidence intervals obtained by bootstrapping over loci. F_it values (data not shown) are not significantly above 0 (P = 0.767 and P = 1 for females and males, respectively) on the basis of 10,000 random permutations. Values and tests were performed on W1 samples (before treatment) with the seven most polymorphic loci defined in Results.

Fig. 2.

Population structure of C. albicans in AIDS patients from Abidjan (pooling method in ref. 23). Squares, male samples; circles, female samples; triangles, males and females combined. If the samples pooled belong to the same reproductive unit (deme), no change in the F_is estimate is expected. F_is increases when populations with different genetic composition are combined; this is the case when samples from W1 and W3 are combined for males and when all males or all females are combined. Bars are 95% confidence intervals obtained by bootstrapping over loci (24).