Metagenomic Analysis of Removable Prosthesis Microbiome with Different Prosthesis Cleanliness.

Objectives: To characterize the microbiome of removable prostheses with different levels of cleanliness using Type IIB Restriction-site Associated DNA (2b-RAD) sequencing and compare the Microbial Index of Pathogenic Bacteria (MIP) between clean and unclean prostheses.
Methods: A cross-sectional study was conducted among participants wearing removable prostheses in Hong Kong. The area of plaque coverage was quantified using a semi-automated planimetric assessment. Whole metagenomic sequencing of 97 prosthesis plaque samples was performed using the 2b-RAD method. Species-level abundance profiles were obtained to determine the MIP for each prosthesis microbiota. The MIP was calculated as the sum of the relative abundance of opportunistic pathogenic bacteria in a microbial community according to 300 published categories of opportunistic pathogenic bacteria by the Chinese Center for Disease Control and Prevention.
Results: The mean percentage of removable prostheses covered with plaque was 24.79%. Forty-two (43.3%) prostheses were deemed ‘unclean’ with a percentage plaque area coverage higher than 25%. The overall microbial evenness and richness in both groups (clean and unclean groups) showed no statistically significant difference. Beta diversity analyses based on Jaccard qualitative and Bray-Curtis quantitative distance matrices revealed significant differences between the two groups (P<0.05). The mean MIP for unclean prostheses (0.46±0.25) was higher than for clean prostheses (0.37±0.29). However, the difference was not statistically significant (P=0.052). The difference was statistically significant (P=0.029) after taking the prosthesis design into account.
Conclusions: Among a community-dwelling sample of participants attending a teaching hospital, approximately half had unclean prostheses as identified by the semi-automated planimetric method. The microbial community of plaque samples from unclean prostheses demonstrated a clear distinction compared with clean prostheses. In addition, a trend was also observed for the increased MIP in the unclean group in comparison with the clean counterpart.