Impact of sexual debut on culturable human seminal microbiota

Micro-organisms are tightly integrated into host-microbiota ecosystem. Microbiota of human semen has been studied so far mostly in case of infertility or prostatitis. We aimed to reveal possible impact of sexual debut on seminal microbiota in healthy young men. The study group included 68 young healthy men, of them 12 men without sexual experience, 11 men with single lifetime sexual partner and 45 men with multiple lifetime sexual partners. Basic semen parameters were similar for all subgroups, and no correlation between sexual experience and WBC counts in semen was found. A man could harbour one to nine different bacteria in his semen; the total concentration of bacteria ranged from 2.3 to 7.3 log(10) CFU/mL of semen. Lower total bacterial concentration and lower bacterial diversity was observed in men without sexual experience than in sexually experienced men (p<0.05), with significant positive correlation between these two parameters (r=0.54; p<0.0001). In conclusion, the sexual debut is associated with the enrichment of seminal microbiota but not with the influx of WBC or changes in basic seminal parameters.