To verify the prevalence of semen bacterial contamination and whether the contamination could decrease sperm quality.
Spermiogram, semen culture, and sperm transmission electron microscopy (TEM) analysis were performed. TEM data were elaborated using a mathematical formula that calculates a fertility index (FI)—able to define patients as fertile or infertile—and the percentage of sperm apoptosis, immaturity and necrosis. We aligned the amino acid sequence of beta-tubulin with protein of the most frequent species isolated from semen.
Patients were divided according to the contaminating species; in each group, we observed fertile individuals, in whom the semen quality was similar to that of controls and infertile men whose sperm quality was significantly decreased, in terms of motility, FI, apoptosis and necrosis. Partial homology between β-tubulin and bacterial proteins was observed.
Sperm bacterial contamination is quite frequent and could contribute to the deterioration of the sperm quality of infertile men.