Recurrent vulvovaginal candidiasis (rVVC) is a condition which, though not linked to mortality, can cause complications and significant psychological, physical and monetary costs. Candida albicans is the most common cause of rVVC. Candida africana is a recently recognised species, very closely related to C. albicans; despite worldwide distribution of C. africana, its role in rVVC is unclear.
A recent study by Naeimi and colleagues analysed 128 Iranian cases of rVVC, in order to discover the incidence of C. africana-caused cases, and to analyse strain homogeneity and drug resistance in these isolates. The close similarity between C. albicans and C. africana makes it difficult to accurately distinguish between these isolates; differences in adherence ability, pathogenicity and biofilm formation however necessitate the need to discriminate between them in clinical settings.
Key methods for identification between C. albicans and C. africana include CHROMagar and PCR. In this study, C. africana produced deep turquoise/green colonies on CHROMagar, compared to the lighter turquoise/green colonies of C. albicans (although colour variation between C. albicans colonies can occur).
PCR analysis identified 119 out of 128 isolates as C. albicans. Due to hyphal wall protein 1 (HWP1) polymorphisms these were subject to reidentification and 10/119 (8.4%) were subsequently identified as C. africana. 100% sequence similarity was observed between Iranian C. africana strains, though variation was observed between the Iranian strains and isolates from other parts of the world.
C. africana is susceptible to conventional antifungal drugs, but resistance to flucytosine, voriconazole and terbinafine has been reported. C. africana isolates in this study were only tested against fluconazole, and were all found to be susceptible.
In conclusion, C. africana was isolated from 7.8% of the rVVC patients in this study; a significant proportion. Both conventional and molecular techniques are used to distinguish between C. albicans and C. africana.