Correlation between the relative abundance of oral bacteria and Candida albicans in denture and dental plaques.

Objectives: The opportunistic fungus Candida albicans is a component of denture plaque and is associated with denture-related stomatitis. Inter-kingdom interactions between C. albicans and bacteria exist in such multi-species biofilms, which may affect the microbial composition of the plaque. This study was performed to investigate the bacterial composition of denture plaques, and the correlation between the relative abundance of these bacteria and C. albicans.

Methods: Thirty denture plaque and 16 dental plaque samples were collected from 18 denture wearers (mean age, 80.3 years). After DNA extraction, a meta 16S rDNA amplicon library was constructed using PCR primers targeting the V3-V4 hypervariable region of bacteria. The amplicon was evaluated by high-throughput sequencing, followed by bacterial population analysis. The concentrations of both C. albicans DNA and total bacterial DNA were determined by real-time PCR. The correlation between the relative abundance of each bacterial genus and C. albicans was analyzed through Spearman's rank correlation.

Results: The genera Streptococcus, Lactobacillus, Rothia, and Corynebacterium were found to be more abundant in dentures than in dental plaques. The predominant bacteria in healthcare-associated pneumonia also inhabited denture surfaces. C. albicans was positively correlated with three acidogenic bacteria and negatively correlated with Leptotrichia and pathogens associated with periodontitis and endocarditis.

Conclusions: Dentures may be significant reservoirs of pathogens causing aspiration pneumonia. Bacteria showing negative correlation with C. albicans, such as Leptotrichia, may be useful for controlling the growth of C. albicans in antifungal therapies.