Candida dubliniensis screening using the germ tube test in clinical yeast isolates and prevalence of C. dubliniensis in Korea

Lab-Based Retrospective 10-Year Analysis Shows Seasonal Variation of Vaginal Candida Infection Rates in Belgium

Candida vulvovaginitis is a frequent condition, and although several risk factors are known, its behavior is still enigmatic. The seasonal influence of climate conditions and living habits on its prevalence was studied. In a retrospective lab-based cohort over 10 years, we studied the prevalence of Candida in 12,941 vaginal cultures taken from women attending a vulvovaginitis clinic. The prevalence of non-albicans and albicans species were compared per month to detect differences in positivity rates in summer versus winter months. Chi-square and chi-square for trend were used. Of the 2109 (16.3%) Candida spp. positive swabs, 201 (1.0%) revealed non-albicans species, varying between 1.0% and 2.0% per month, but without significant monthly differences. Over the 10 years, compared to other months, vaginal Candida was more frequent in June (19.0%, p = 0.008) and less frequent in December (14.5%, p = 0.04). The Candida prevalence was 15.5% in summer (June/July/August) versus 14.0% in the winter (Dec/Jan/Feb, p = 0.04). Change in temperature, dietary habits, and bodily adaptations due to increased amount of sunlight were discussed as potential pathophysiological mechanisms to explain the excess of Candida in summertime. Further confirmatory research would be beneficial. Women at risk for Candida vulvovaginitis should pay more attention to living habits in summertime to avoid recurrences.

The usefulness of DNA sequencing after extraction by Whatman FTA filter matrix technology and phenotypic tests for differentiation of Candida albicans and Candida dubliniensis

Since C. dubliniensis is similar to C. albicans phenotypically, it can be misidentified as C. albicans. We aimed to investigate the prevalence of C. dubliniensis among isolates previously identified as C. albicans in our stocks and to compare the phenotypic methods and DNA sequencing of D1/D2 region on the ribosomal large subunit (rLSU) gene. A total of 850 isolates included in this study. Phenotypic identification was performed based on germ tube formation, chlamydospore production, colony colors on chromogenic agar, inability of growth at 45 °C and growth on hypertonic Sabouraud dextrose agar. Eighty isolates compatible with C. dubliniensis by at least one phenotypic test were included in the sequence analysis. Nested PCR amplification of D1/D2 region of the rLSU gene was performed after the fungal DNA extraction by Whatman FTA filter paper technology. The sequencing analysis of PCR products carried out by an automated capillary gel electrophoresis device. The rate of C. dubliniensis was 2.35 % (n = 20) among isolates previously described as C. albicans. Consequently, none of the phenotypic tests provided satisfactory performance alone in our study, and molecular methods required special equipment and high cost. Thus, at least two phenotypic methods can be used for identification of C. dubliniensis, and molecular methods can be used for confirmation.

The first Korean case of candidemia due to Candida dubliniensis

Candidemia due to uncommon Candida spp. appears to be increasing in incidence. C. dubliniensis has been increasingly recovered from individuals not infected with HIV. Identification of C. dubliniensis can be problematic in routine clinical practice due to its phenotypic resemblance to C. albicans. We report the first case of C. dubliniensis candidemia in Korea, which occurred in a 64-yr-old woman who presented with partial seizure, drowsiness, and recurrent fever. Germ-tube positive yeast that was isolated from blood and central venous catheter tip cultures formed smooth, white colonies on sheep blood agar and Sabouraud agar plates, indicative of Candida spp. C. dubliniensis was identified using the Vitek 2 system (bioMerieux, USA), latex agglutination, chromogenic agar, and multiplex PCR. The blood isolate was susceptible to flucytosine, fluconazole, voriconazole, and amphotericin B. After removal of the central venous catheter and initiation of fluconazole treatment, the patient's condition gradually improved, and she was cleared for discharge from our hospital. Both clinicians and microbiologists should be aware of predisposing factors to C. dubliniensis candidemia in order to promote early diagnosis and appropriate treatment.

First isolation of Candida dubliniensis from oral cavities of dermatological patients in Nanjing, China

Candida dubliniensis is an emerging pathogen capable of causing both superficial and systemic infections. Although C. dubliniensis and C. albicans are phenotypically similar, the two species differ in terms of epidemiology and the ability to rapidly develop resistance to fluconazole. C. dubliniensis is primarily associated with oral candidiasis of human immunodeficiency virus (HIV)-infected individuals. In this study, we describe the first recovery of C. dubliniensis from oral cavities of non-HIV-infected patients with dermatological diseases in Nanjing, China. The isolates were phenotypically characterized as C. dubliniensis by their production of brown rough colonies and chlamydospores on tobacco agar and their inability to grow on hypertonic Sabouraud dextrose agar or to assimilate xylose or α-methyl-D-glycoside. The species identification was subsequently confirmed by amplification and sequencing of the internal transcribed spacer region (ITS). Three C. dubliniensis isolates out of 128 (2.3%) presumptive C. albicans/C. dubliniensis ones were finally identified. Further sequence analysis separated the three isolates into two of the four reported ITS genotypes. Antifungal susceptibility testing showed that they were susceptible to fluconazole, itraconazole, voriconazole, micafungin, and amphotericin B. This study adds to the accumulating evidence that C. dubliniensis is widely distributed in non-HIV-infected populations worldwide.