Characterization of Candida isolates from South African pregnant and non-pregnant women.

Abstract

Candida infections are a serious health threat to women. Characterization of Candida isolates has become the gold standard method used in determining antimicrobial susceptibility profiles and resistance mechanisms in vaginal Candida infections. However, there is a lack of data on the antimicrobial susceptibility profiles of South African Candida isolates to amphotericin B. This study investigated antimicrobial resistance profiles and genotypes of Candida isolated from South African pregnant and non-pregnant women. This study was a sub-study of a larger study which involved the diagnosis of vaginitis and vaginosis pathogens in women. For the parent study, n=150 women were recruited from the King Edward VIII hospital in Durban, KwaZulu-Natal, South Africa. The women enrolled in the parent study were; 18 years and older, were willing to provide written informed consent and were willing to provide self-collected vaginal swabs. A total of 72 Candida isolates were obtained by culture. Of the 72 isolates, 31 isolates were obtained from pregnant women and 41 isolates were from non-pregnant women. The isolates were typed using the ABC genotyping method. Susceptibility testing was performed using the broth microdilution assay to measure the minimal inhibitory concentrations (MICs) for clinical isolates to amphotericin B. The Candida albicans ATCC 10231 strain was used as a control strain, and untreated cultures of the respective isolates were used as growth controls. Descriptive characteristics of the study participants according to Candida status were presented as frequencies and percentages. Comparisons by Candida status in the descriptive characteristics were performed using Chi square tests with a 5% significance level. P-values ≤0.05 were considered significant. All analyses were conducted using STATA. The prevalence of Candida in the study population was 48.0% (72/150). All the isolates (100%) were confirmed to be C. albicans as per the germ tube test and quantitative polymerase chain reaction (PCR) using primers and probes specific for C. albicans. All 72 isolates (100%) produced positive PCR results for C. albicans. The majority of the isolates (45/72; 62.5%) yielded a 450bp band which was assigned Genotype A. Of the 72 isolates, 19 isolates (26.4%) yielded a band size of 840bp and was assigned Genotype B. A total of 11.1% (8/72) of the isolates yielded band sizes of 450bp and 840bp which was Genotype C. Of the 72 isolates tested, 79.2% (57/72) of the isolates were resistant to amphotericin B (MIC >1ug/ml) and 20.8% (15/72) of the isolates were susceptible to amphotericin B (MIC ≤ 1 ug/ml). When linking MIC patterns to distribution of genotypes, it was observed that the majority (80%) of the isolates which were assigned genotype A were resistant to amphotericin B. When linking clinical symptoms with the distribution of genotypes, it was observed that the majority (58.8%) of women who reported having current symptoms of abnormal vaginal discharge carried genotype A. Genotype A was most prevalent in women who had been treated for vaginal infections in the past and in women who were HIV positive with prevalence of 64.1% and 60.8%, respectively. genotype A was most prevalent in the non-pregnant women with a prevalence of 63.4%. Genotype A was prevalent (61.3%) amongst the pregnant women and the majority (66.7%) of the HIV negative women had Candida infections which belonged to genotype A. The prevalence of Candida was shown to be high in both pregnant and non-pregnant women in this study. This study also found a high level of resistance to the antifungal amphotericin B. Currently in our local setting, resistance patterns to the commonly used antifungals to treat Candida infections are not being monitored. There is a need for antifungal resistance monitoring in order to reduce the risk of future persistent and untreatable infections.