Penile microbiome in histopathologically confirmed lichen sclerosus: a comparative study of urethral and preputial swabs.

PURPOSE: The study examines the microbial compositions of patients with lichen sclerosus (LS) compared to control group, and individuals with other penile conditions. The aim is to address the critical question regarding the etiology of penile LS and to explore the potential involvement of the microbiome in its pathogenesis. METHODS: In this prospective single-centre study, 73 uncircumcised male patients undergoing circumcision for phimosis were enrolled between January 2023 and April 2024. Foreskin and urethral swabs were obtained prior to surgery to isolate Candida, aerobic, and anaerobic microorganisms and sexually transmitted pathogens. Patients were categorised into LS (n = 44) and non-LS (n = 29) groups based on histopathological findings. Additionally, a control group, which consisted of patients with healthy foreskin, has been specified to conduct further analysis. RESULTS: No statistically significant differences were observed in the prevalence of specific bacterial or viral pathogens between the LS and non-LS groups and between the LS/non-LS and control group. The most common commensal organisms were Staphylococcus coagulase-negative (48% and 34% respectively) and Corynebacterium spp. (27% and 17% respectively), whereas Enterococcus faecalis (14%) and Escherichia coli (16%) were the most frequent pathogens in LS group, and Streptococcus agalactiae (21%) was the most abundant pathogen in non-LS group. HPV was detected in 5% of patients with LS and in 14% of patients without LS. There were no statistically significant differences in CRP levels and BMI. In exploratory multivariable models adjusting for age and BMI, the presence of Streptococcus agalactiae was associated with lower odds of LS (OR 0.19; 95% CI 0.04-0.92; p = 0.04; FDR = 0.07); however, given limited power, these results should be interpreted cautiously. CONCLUSIONS: Our study demonstrated no significant association between specific microbial or viral profiles and penile lichen sclerosus. However, due the fact that the culture-based approach employed in this study may underestimate the diversity of the penile microbiome, further research is warranted.