Background: Molecular biologic identification of bacteria in clinical specimens by ribosomal RNA gene sequences (rDNA) promises to overcome difficulties in culturing fastidious organisms and may aid in the identification of new disease agents. We have developed an assay system that avoids detection of commensals and has screened out possible reagent contaminants, both of which limited the interpretation of previous molecular biologic studies of prostate biopsies. In a previous pilot study from our laboratory, our assay system detected bacterial rDNAs in only approximately half of a cohort of 45 semen specimens, suggesting that bacterial infection of semen is not a consistent finding and may be clinically significant.
Methods: Bacterial rDNAs were amplified by polymerase chain reaction, cloned and sequenced from three semen specimens (one before and two following the biopsy) and three prostate biopsy cores to investigate the cause of an elevated PSA in a man with chronic prostatitis. A total of 62 bacterial rDNA sequences were analyzed.
Results: The semen specimens, but not the prostate biopsies, contained rDNAs previously identified in semen: Corynebacterium pseudogenitalium and Finegoldia magna. One of the biopsies, but not the semen specimens, contained Aeromonas hydrophila, an organism previously identified in prostate biopsies. An uncommon, but clinically significant organism, Pseudomonas stutzeri, was detected in all 3 semen specimens and 2 of the prostate biopsies.
Conclusions: This study proves the feasibility of and potential clinical value of applying molecular biologic techniques to study bacterial detection in male GU tissues and secretions. Though usually considered a contaminant, P. studzeri may be an opportunistic pathogen in compromised hosts. The unique immunomodulation within the prostate gland may render it susceptible to infection with previously undetected organisms that may play a role in prostate disease. Further studies in men with chronic prostatitis, elevated PSA, and prostate cancer are planned.