# Candida dubliniensis in Japanese Oral Microbiota: A Cross-Sectional Study of Six Geographic Regions in Japan

## TL;DR

This study examines the presence of Candida dubliniensis in the mouths of healthy and diseased individuals across six regions in Japan, finding geographic variations in its carriage rate.

## Contribution

The study provides the first cross-sectional analysis of C. dubliniensis carriage in Japan, revealing geographic distribution patterns and novel genotypes.

## Key findings

- C. dubliniensis carriage rates were low in central Japan but high in northern and southern regions.
- Genotype I was most common, but new genotypes were also identified in Japanese populations.
- C. dubliniensis showed low protease productivity and higher antifungal susceptibility compared to C. albicans.

## Abstract

Introduction: Candida dubliniensis was reclassified from the C. albicans genotype D, and reports show its frequent detection in HIV-positive individuals and easy acquisition of antifungal drug resistance. However, the oral carriage rate in healthy people and contribution to candidiasis in Japan is unclear. Methods: We conducted a cross-sectional survey of the C. dubliniensis carriage rate, performed genotyping and tested antifungal drug susceptibility and protease productivity. Specimens from 2432 Japanese subjects in six regions (1902 healthy individuals, 423 with candidiasis individuals, 107 HIV-positive individuals) were cultured using CHROMagarTMCandida, and the species was confirmed via 25S rDNA amplification and ITS sequences analyzed for genotyping. Results: The C. dubliniensis carriage rate in healthy Japanese was low in the central mainland (0–15%) but high in the most northerly and southerly areas (30–40%). The distribution of these frequencies did not differ depending on age or disease (HIV-infection, candidiasis). Genotype I, previously identified in other countries, was most frequent in Japan, but novel genotypes were also observed. Six antifungal drugs showed higher susceptibility against C. albicans, but protease productivity was low. Conclusions: Oral C. dubliniensis has low pathogenicity with distribution properties attributed to geography and not dependent on age or disease status.