Objective: To determine if the presently used bacterial detection techniques provide accurate and complete profiles of microorganisms found in human semen.
Design: Routine bacterial cultures and molecular biology techniques using polymerase chain reaction (PCR), with a universal eubacterial primer, cloning, then sequence analysis were used to detect bacteria (culturable or nonculturable) in the semen.
Setting: University and hospital-based research laboratory.
Patients: Thirty infertile men and nine semen donors, all with no symptoms of a urinary tract infection, donated semen for the study.
Interventions: None.
Main outcome measures: Detection of bacteria using routine cultures and molecular biology techniques.
Results: Using PCR, we found > 10(4) bacteria/mL in the semen of 66% of the infertile asymptomatic men and 66% of the semen donors. This contrasts with our routine culture results which detected "significant" bacteriospermia in only 27% of the infertile men and in none of the preselected semen donors. From four of these semen specimens, DNA sequence analysis identified an average of nine different bacterial species per specimen, with close to 90% of the species being anaerobes.
Conclusions: These data indicate that the present microbiologic detection methods underestimate the incidence of significant bacteriospermia, particularly anaerobic bacteria. The molecular biologic methods should help researchers confirm or refute the role of infection in male infertility.