The antibacterial activity of semen and its relation to semen proteins

Search for uro-genital tract infections in patients with symptoms of prostatitis. Studies on aerobic and strictly anaerobic bacteria, mycoplasmas, fungi, trichomonads and viruses

Seventy-nine patients with symptoms of nonacute prostatitis and 20 healthy volunteers were examined for uro-genital tract infection with bacteria, mycoplasmas, fungi, trichomonads and viruses. No differences in the results of the bacterial cultures were found between the patients and the controls. In only a few cases were established urinary tract pathogens found, but in no instance were these findings reproducible in later specimens. The cultures of the expressed prostatic fluids and the samples of semen gave no information of the occurrence of bacteria over and above that obtainable from examination of the urethral specimens. Significant bacteriuria was not found in any of the patients. Though Neisseria gonorrhoeae could not be isolated from any of the subjects, immunofluorescent studies revealed such organisms in seminal fluid in 8% of the patients. Nine of the patients had 1 to 3 years been considered successfully treated for gonorrhoea. Five of these nine patients were still found to harbour gonococci, as judged from the immunofluorescent studies. Corynebacterium vaginale was recovered in an equally low frequency (5%) from the patients and the volunteers. There was no significant difference in the incidence of T-mycoplasmas between the patients (46%) and the controls (35%), while Mycoplasma hominis was only found in the patients (10%). Trichomonas vaginalis could not be detected in wet smears of expressed prostatic fluid in any of the subjects, but could be cultured from one such specimen. Metacycline treatment (performed according the double blind cross-over technique) was studied for effects on the bacterial flora. In about 10% of the patients, an earlier not observed relative dominance of gram-negative rods was found on the cultures made after the therapy. Candida albicans was only isolated from the patients. It was found more often after (24%) than before the (15%) treatment. Complement-fixing antibodies to N. gonorrhoeae, cytomegalovirus and Chlamydia were found in 10, 19, and 33% of the patients, respectively. The corresponding figures for the healthy males were 0, 20 and 5%.

Antimicrobial activity of human seminal fluid

The antibacterial, antifungal and antimycoplasmal activity of human semen was studied. Gram-positive aerobic bacterial species i.e. staphylococci, but not gram-negative aerobic bacteria, were inhibited by seminal fluid in vitro. Neither were anaerobic gram-positive or gram-negative bacteria, nor Candida or Mycoplasma inhibited. Semen of healthy males had a higher antibacterial effect on S. albus than that of patients with symptoms of chronic prostatitis. There was a positive correlation between the antibacterial power of the semen of the patients studied and their content of zinc and magnesium, while no correlation was found with fructose and lysozyme or the number of spermatozoa in any of the groups. A positive correlation was found between the antibacterial capacity and the volume of the ejaculate in the patients but not among the controls. The antibacterial substance(s) was dialysable, ether-extractable, resistant to boiling and partly to storage at room temperature. The addition of EDTA, tranexamic acid and ammonium reineckate to semen did not influence the antibacterial effect, which was, however, slightly inhibited by sodium polyanethol sulphonate. The nature of possible antibacterial substances in semen is discussed.