Investigating the role of cranberry products on gut and vaginal microbial modulation in healthy women for urinary tract infection prevention

Ahhria Theresa B.F. Kirkendall

doi:10.7273/000008371

Cranberry phytochemicals have historically been associated with urinary tract health, yet their role in the gut-urogenital axis in women for urinary tract infection prevention remains poorly understood. This dissertation investigated how various cranberry products modulate microbial composition across complementary in vitro and in vivo models. The studies herein establish a microbiome-mediated framework through which cranberry consumption may reinforce mucosal homeostasis and indirectly reduce urinary tract infection (UTI) risk. In vitro fermentation in an anaerobic chamber of cranberry press cake and seed fractions revealed distinct yet complementary microbial trajectories over 32 hours in an incubator shaker at 37℃ and 120 RPM. Both substrates stimulated saccharolytic fermentation, where press cake and seeds selectively enriched Bacteroides and secondary butyrate producers such as Clostridium XIVa and Subdoligranulum (p < 0.05). These findings support prebiotic potential of cranberry byproducts for promoting short-chain fatty acid and phenolic-acid metabolism as indirect mechanisms beneficial for urinary tract health. A randomized, double-blind, placebo-controlled, crossover dietary intervention (45 days) with daily low-calorie cranberry juice (LCCJ, 8 fl oz) examined the effects on fecal and vaginal microbial modulation in healthy women (n = 47). Overall fecal microbial stability was maintained while eliciting subtle, compositionally favorable shifts. Phylum-level analysis revealed a significant increase (p < 0.05) in Bacteroidetes following LCCJ intake, aligning with enrichment of saccharolytic taxa observed across both in vitro and in vivo models. The α- and β-diversity indices remained stable (p > 0.05), yet SIMPER analysis revealed enrichment of saccharolytic and butyrogenic taxa including Faecalibacterium and Anaerostipes alongside minor declines in proinflammatory genera such as Blautia and Collinsella. Enterotype modeling confirmed microbial stability, suggesting that cranberry phytochemicals support intestinal balance rather than restructuring. Parallel vaginal microbiome analyses following the same methodology from the gut microbiome with RStudio® indicated modest but biologically meaningful changes during the LCCJ phase. Richness and Shannon diversity decreased (p < 0.05) while evenness increased, reflecting consolidation toward Lactobacillus-dominant profiles. Phylum-level shifts showed increased Firmicutes and decreased Actinobacteria consistent with reduced dysbiotic anaerobes and enhanced mucosal resilience. Further genus-level analyses in directional relative abundance shifts revealed a reduction (p < 0.05) in anaerobes associated with vaginal infections, thus supporting a homeostatic vaginal microbiome potentially protective against UTIs. Integrative comparisons across systems revealed directionally consistent microbial modulation favoring saccharolytic, butyrogenic, and lactic acid–producing taxa. These patterns suggest that cranberry phytochemicals act through metabolite-mediated crosstalk along the gut–urogenital axis, generating SCFAs and phenolic intermediates that reinforce epithelial integrity while discouraging uropathogen colonization. Collectively, the findings expand the classical urinary anti-adhesion paradigm to a broader, microbiome-centered mechanism in which cranberry consumption stabilizes mucosal microbial ecosystems, thereby promoting systemic homeostasis conducive to UTI prevention.

Investigating the role of cranberry products on gut and vaginal microbial modulation in healthy women for urinary tract infection prevention

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