Microbiota of the Urogenital Tract

Healthy adult bladders may contain low-biomass microbial communities, including facultative anaerobes like Proteus mirabilis and E. coli.

Proteus mirabilis produces urease, which breaks down urea into ammonia. This sometimes causes an abnormal increase in urine pH, leading to the formation of stones.

The distal urethra also hosts similar bacterial species in higher abundance. When pH or microbiota balance shifts, some of these species can become pathogenic.

The penile microbiota harbors bacterial genera like Corynebacterium and Staphylococcus.

In the vagina, low glycogen and neutral pH, especially before puberty, favor colonization by staphylococci, streptococci, and corynebacteria.

Whereas during reproductive years, the vaginal microbiota is dominated by members of the genus Lactobacillus.

This dominance is sustained due to a mildly acidic environment created by Lactobacillus species which ferments glycogen into lactic acid.

The resulting low pH also largely inhibits opportunistic pathogens like Candida species and E. coli.