Genetic relatedness of Candida strains isolated from women with vaginal candidiasis in Malaysia

Abstract

The aims of this study were to compare the genetic relatedness of: (i) sequential and single isolates of Candida strains from women with recurrent vaginal candidiasis (RVC); and (ii) Candida strains from women who had only one episode of infection within a 1-year period. In total, 87 isolates from 71 patients were cultured, speciated and genotyped by random amplification of polymorphic DNA (RAPD) analysis. Patients were categorized into three groups, namely those with: (i) a history of RVC from whom two or more yeast isolates were obtained (group A); (ii) a history of RVC from whom only a single isolate was obtained (group B); and (iii) a single episode of vaginal candidiasis within a 1-year period (group C). Six yeast species were detected: Candida albicans, Candida glabrata, Candida lusitaniae, Candida famata, Candida krusei and Candida parapsilosis. Interestingly, the prevalence of non-albicans species was higher in group A patients (50 %) than in patients in groups B (36 %) or C (18·9 %). Eighty RAPD profiles were observed, with a total of 61 polymorphic PCR fragments of distinct sizes. Clustering analysis showed that, overall, the majority of patients in group A had recurrent infections caused by highly similar, but not identical, sequential strains [mean pairwise similarity coefficient (S AB ) ¼ 0·721 AE 0·308]. The range of mean S AB values for intergroup comparisons for C. albicans isolates alone was 0·50-0·56, suggesting that there was no significant relatedness between strains from different groups. Genetic similarity of C. albicans isolates from patients in group A was lower than that of C. albicans isolates from patients in group C (mean S AB ¼ 0·532 AE 0·249 and 0·636 AE 0·206, respectively); this difference was statistically significant (P ¼ 0·036). These results demonstrate that the cause of recurrent infections varies among individuals and ranges between strain maintenance, strain microevolution and strain replacement; the major scenario is strain maintenance with microevolution. They also show that C. albicans strains that cause recurrent infections are less similar to each other than strains that cause one-off infections, suggesting that the former may represent more virulent subtypes.

Diversity of Pathogenic Candida Species Colonizing Women with and without Candida Vaginitis in Dar es Salaam Region, Tanzania

“…These different Candida species have been associated with differences in the morphotype and virulence factors such as germ tube and mycelia formation, proteinase secretion, the changes in vaginal pH, phenotypic switching and ability to cause vaginal candidiasis (Sobel et al, 1981;Sobel, 1985;Hunter et al, 1989;Cutler, 1991;De Bernardis, et al, 1993;Cassone et al, 1995;Hube, 1996;Samaranayake et al, 2003;. However, a significant increase in non-albicans Candida species and formation of virulence factors have been reported to be associated with recurrent Candida vaginitis (Sobel, 1992;Sobel, 1998;Chong, et al, 2003;.…”

“…The most common vaginal isolate include C. albicans with a prevalence of 70-90% and less frequently non-albicans Candida species such as C. tropicalis, C. glabrata (Torulopsis glabrata), C. kefyr (C. pseudotropicalis), C. krusei, C. famata, C. parapsilosis, and C. lusitaniae (Xu et al, 1999;Abu-Elteen, 2001;Chong et al, 2003;. These different Candida species have been associated with differences in the morphotype and virulence factors such as germ tube and mycelia formation, proteinase secretion, the changes in vaginal pH, phenotypic switching and ability to cause vaginal candidiasis (Sobel et al, 1981;Sobel, 1985;Hunter et al, 1989;Cutler, 1991;De Bernardis, et al, 1993;Cassone et al, 1995;Hube, 1996;Samaranayake et al, 2003;.…”

Lack of association between genotypes and virulence factors in C. albicans strains isolated from vaginal secretion

“…The genotypes of this yeast have been associated with different infection sites (18) and with susceptibility to antifungal drugs (20). Recently, Chong et al (4), in a study of genetic similarities by random amplification of the polymorphic DNA (RAPD) of Malaysian patients with VVC and RVVC, found that patients with RVVC are more frequently colonised by the same isolate of Candida. However, little is known about the relation of the genotypes with the virulence capacity of C. albicans in the vagina.…”

“…About 20 to 25% of healthy and completely asymptomatic women present positive vaginal secretion cultures for this fungus. Around 75% of adult women have at least one episode of vulvovaginal candidiasis (VVC) during their life, with prevalence of C. albicans in 70-90% (4). Some of these patients will experience episodes again and 5% will suffer recurrent VVC (RVVC) (13).…”

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“…Chong et al [90] in their study in Malaysia showed that C. albicans that cause RVVC are less similar to each other than the strains causing sporadic VVC, thus suggesting that the former may represent more virulent sub-types [90]. Soll et al [91] reported that although the genotype remains the same there is phenotype switching of C. albicans in RVVC [91] and Schroppel et al [92] observed yeast genetic instability with repeated courses of antifungal treatments [92].…”