Noninflammatory comedones have greater diversity in microbiome and are more prone to biofilm formation than inflammatory lesions of acne vulgaris

Background: The ability of Cutibacterium acnes strains to form biofilms has been correlated with their virulence. Objective: This study examined biofilm and skin microbiota in acne patients in order to understand their role in the development of acne lesions. Methods: Thin sections of punch biopsy specimens of (i) uninflamed comedones, (ii) inflammatory lesions, and (iii) uninvolved adjacent skin of acne patients were examined. Epiflourescence and confocal laser scanning microscopy were used for biofilm detection, and pyrosequencing with taxonomic classification of 16s rRNA gene amplicons was used for microbiota analysis. Results: Of the 39 skin specimens from patients with mild-moderate acne (n = 13) that were studied, nine (23%) contained biofilm. Among these specimens, biofilm was most frequently detected in comedones (55.6%) and less frequently in inflammatory papules (22.2%) and uninvolved skin (22.2%). Comedones demonstrated the highest mean alpha diversity of all the lesion subtypes. The relative abundance of Staphylococcus was significantly higher in comedones (11.400% ± 12.242%) compared to uninvolved skin (0.073% ± 0.185%, P = 0.024). Conclusions: The microenvironment of the comedone differs from that of inflammatory lesions and unaffected skin. The increased frequency of biofilm in comedones may account for the lack of host inflammatory response to these lesions.