Smegma may provide a place to breed for harmless bacteria, but it could also harbor pathogens, more likely in uncircumcised men. Gram-negative bacteria such as Escherichia coli, Pseudomonas spp., Proteus spp., and Klebsiella spp. are predominantly found in and around the urethra (UR), with circumcision increasing the presence of coagulase-negative Staphylococcus spp. and decreasing the number of gram-negative pathogens and enterococci. After circumcision, relatively low levels of Staphylococcus aureus and no changes in S. aureus prevalence are reported.
In one study, the culture of organisms from the coronal sulcus yielded 41.6% colonized with S. aureus, 3.5% with Enterococcus spp., 22.9% with a gram-negative bacterium (E. coli, Klebsiella spp., or Pseudomonas aeruginosa), 1.6% with an anaerobe (Clostridium), 0.3% with a yeast (Candida albicans), and 60.0% with any pathogen. A coagulase-negative Staphylococcus sp. was present in 97.4% of all study participants. Gram-negative pathogens were more prevalent among HIV-infected participants (22.7%) and TB-infected individuals (30.4%) as compared with healthy men (6.0%) (P=0.003). Urethral colonization demonstrated similar results and patterns.