Evaluation of overtime phenotypic variation of yeasts in chronic vulvovaginal candidosis cases

Abstract

Chronic vulvovaginal candidosis results either from reinfection or from the ability of Candida spp. to persist in the vulva and/or vagina. Persistence is usually associated with increased antifungal (mainly azoles) resistance rates, which can explain treatment failure, and/or increased expression of virulence factors by Candida spp. The aim of this study was to assess the mechanisms leading to Candida spp persistence, by studying sequential isolates from women with chronic vulvovaginal candidosis, focusing on strains genotypes, azole resistance and ability to form biofilms along the period of clinical evaluation. The strains were identified at species level by automated analysis of biochemical profiles and molecular typing evaluated by polymorphic DNA analysis. The capacity to form biofilm was assessed with a microtiter plate assay. Fluconazole susceptibility was determined by the microdilution broth assay at both pH 7 (following the recommended guideline) and pH 4.5 (as representative of vaginal pH). We studied samples from 17 clinically recurrent cases. In 53% of the chronic cases there were two or more isolates that had a phylogenetic relationship while the remaining (47%) were caused by different species. In those cases where related strains were involved in recurrence, we verified an increase in MIC at pH 7 and also an increased capacity to form biofilms over time. Significant correlation between these two parameters was observed only in cases caused by C. glabrata, evidencing the importance of these two factors to enhance persistence in the vaginal mucosa for this particular species. Lay Abstract Chronic vulvovaginal candidosis (VVC) affects millions of women worldwide. We found that persistence of the same Candida strain on the vaginal mucosa does not account for the great majority of VVC cases. Moreover, modulation of biofilm formation and azole resistance overtime was investigated.

Uncovering the Yeast Diversity in the Female Genital Tract: An Exploration of Spatial Distribution and Antifungal Resistance

“…Similarly, other studies that analyzed yeast isolates from vaginal samples of both infection and asymptomatic cases also detected differences in the proportions of the species obtained, as can be seen in four of the studies presented in Table 3. Considering that in chronic cases of vulvovaginal candidosis investigators reported that, in approximately 53% of these cases, the episodes were due to genetically related isolates [26], we decided to count each species only once per patient per anatomical site in order to avoid characterizing the same isolate that could have survived between infections.…”

Migration and standing genetic variation in vaginal and rectal yeast populations in recurrent vulvovaginal candidiasis

“…The earliest studies examined diversity by looking at 'resistogram' or phenotypic profiles of strains, by typing strains based on their ability to grow in a panel of diverse chemical challenges (45)(46)(47). This was followed by studies using many different methods of genomic profiling to assess relatedness among strains, such as rDNA restriction fragment length (48), DNA/PCR fingerprinting (40,(49)(50)(51), CHEF gel analysis (52), microsatellite loci (53)(54)(55)(56), and randomly amplified polymorphic DNA (RAPD) (51,(57)(58)(59). The highest genomic resolution and an ability to accurately map phylogenetic relationships among divergent strains come from recent studies that have used multilocus sequence typing (MLST) (18,60,61) and one very small study that employed whole genome sequencing (WGS) (62).…”