A cross-sectional study on the effects of intravesical BCG on urinary microbiota in bladder cancer patients.

Background: Urinary bladder cancer is among the most common malignancy worldwide. Despite surgical interventions and regular surveillance, recurrence and progression to advanced disease are observed in patients. Intravesical administration of Bacillus Calmette-Guérin (BCG) could reduce bladder cancer recurrence and progression in patients with intermediate- and high-risk non-muscle-invasive bladder cancer (NMIBC). Nonetheless, not all patients respond well to BCG treatment. We aim to evaluate whether bacteria profiles were altered after BCG administration.

Methods: In this cross-sectional study, we investigate the differences in urinary microbiome between non-cancerous controls, bladder cancer patients undergoing surveillance cystoscopy, and patients with BCG administration (post-BCG). The V4 regions of the 16S rRNA gene were sequenced, and alpha-diversity and beta-diversity were analyzed. Taxonomic differences between groups and metabolic function analysis of bacteria groups were investigated.

Results: Comparing to the other two groups, the proportion of Pseudomonas, Lactococcus, and Bacillus were increased in the post-BCG group. Superpathways of L-phenylalanine biosynthesis, L-tyrosine biosynthesis, ubiquinol-7, 8, 9, 10 biosynthesis, lipopolysaccharide biosynthesis, glucose degradation oxidative, and 4-hydroxyphenylacetate degradation were significantly enhanced in the post-BCG group.

Conclusion: Results demonstrated that urinary bacteria profiles were distinguished between controls and post-BCG patients. Certain bacteria genus was shown to enhance in post-BCG patients, revealing that the change in the urinary microbiome might be associated with BCG treatment.