Background: To investigate the microbiome composition in individuals with and without rosacea and correlate findings to individual factors that may affect facial cutaneous and enteric microbiome composition. Methods: Participants with and without rosacea (as determined by a board-certified dermatologist) were surveyed regarding factors that may affect the facial cutaneous/enteric microbiome. Microbiome samples were collected, analyzed for 16S sequences, and mapped to an optimized version of existing databases. R was used to perform Mann-Whitney/Kruskal-Wallis test for categorical comparisons. Correlation between two continuous variables was determined with linear regression models. Primary Component Analysis (PCoA) plots employed Monte Carlo permutation test to estimate p-values. All p-values are adjusted for multiple comparisons with the false discovery rate (FDR algorithm) using Benjamini-Hochberg. Results: 84 individuals with rosacea and 44 controls were evaluated. Individuals with rosacea were more likely to currently own pets (p = 0.029) and consume more alcohol (p = 0.006). Absolute bacteria abundance were similar in facial cutaneous (p = 0.36) and enteral microbiome (p = 0.29). Facial cutaneous microbiome showed significantly decreased richness and evenness (OTU: p = 0.019; Shannon: p = 0.049) and a three to four-fold decrease in abundance of 8 distinct cutaneous bacterial genera in rosacea. Enteral microbiome analysis showed significant reduction in abundance of Ruminococcaceae (FDR = 0.002) and Blautia (FDR < 0.001) and increase in Prevotellaceae (FDR = 0.024) in rosacea. Conclusion: Environmental factors may alter relative abundances of specific microbial genera and lead to microbiome diversity. Further studies with increased sample sizes and higher severity cases may further elucidate the role of dysbiosis in rosacea.

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