Long-term storage of boar seminal doses contaminated with Proteus vulgaris: A dose-dependent effect on sperm motility and sperm-bacteria interaction.

This study evaluated how Proteus vulgaris affects sperm quality and sperm-bacteria interaction in stored semen samples. A strain of P. vulgaris resistant to streptomycin, penicillin, lincomycin and spectinomycin was added to boar semen in doses of 10, 10, 10, 10 and 10 CFU/mL. A sample in which there was no addition of P. vulgaris was the negative control. Sperm quality was determined by evaluating sperm motility and morphology using the computer-assisted sperm analysis (CASA) system, and plasma membrane and acrosome integrity using flow cytometry at 0, 1, 2, 4, 6, 8 and 10 days of liquid-storage at 17 °C. At the same time points, pH, sperm agglutination, sperm-bacteria interaction and bacterial growth were also assessed. There was impaired sperm motility when the infective doses of P. vulgaris were equal to or greater than 10 CFU/mL with the effect being dose-dependent (P < 0.05). When infective doses of P. vulgaris were of 10 to 10 CFU/mL there were impairments of plasma membrane and acrosome integrity by Day 1 of storage (P < 0.05), and alkalinisation of the storing medium by Day 4 (P < 0.05). Bacterial adhesion increased when infective dose of P. vulgaris was greater and as duration of storage increased. P. vulgaris had a high affinity for the mid- and principal pieces of sperm cells. It is concluded there were alterations in sperm motility in samples infected with P. vulgaris that were associated with bacterial adhesion and medium alkalinisation.