[Bacterial culture of donor semen: Analysis of results].

Objective: To investigate bacterial infection and the distribution of different bacterial species in the donor semen and the influence of different bacterial counts on semen quality.

Methods: Bacterial colonies in the semen samples from 1 126 donors were counted with the Synbiosis Protocol 3 Automatic Colony Counter and the bacterial species with a colony count ≥10⁴ cfu/ml identified with the VITEK2 Compact Automatic Biochemical Analyzer. The Makler Sperm Counting Board was used to examine the semen quality of the semen samples with a colony count = 0 cfu/ml (n = 22, group A), those with a colony count <10⁴ cfu/ml (n = 22, group B) and those with a colony count ≥10⁴ cfu/ml (n = 22, group C). Univariate analysis was employed for comparison of semen quality among different groups.

Results: Among the 1 126 donor semen samples cultured, 5 (0.44%) showed mixed bacterial contamination and 993 (88.58%) showed none but with growth of a certain species of bacteria, 2.22% (22/993) with a colony count ≥10⁴ cfu/ml, mainly including Streptococcus bovis, tiny bacilli, Staphylococcus epidermis, and Staphylococcus aureus, among which gram-positive and gram-negative bacteria accounted for 95.45% (21/22) and 4.54% (1/22), respectively. Compared with group A, groups B and C manifested significantly reduced total sperm count (［567.5 ± 327.6］ vs ［421.9 ± 155.9］ and ［389.9 ± 110.6］ × 106 per ejaculate, P <0.05) and percentage of progressively motile sperm (［65.0 ± 6.5］ vs ［61.0 ± 3.5］ and ［61.6 ± 4.3］ %, P <0.05). There were no statistically significant differences among the three groups in the semen liquefaction time, semen pH value, total sperm motility or percentage of morphologically normal sperm (P > 0.05). Of the 284 randomly selected semen samples, 34 (11.97%) were found positive for Ureaplasma urealyticum (UU) and no significant difference was observed in the semen quality between the UU-positive and UU-negative samples (P> 0.05).

Conclusions: The bacteria-positive rate is high in the donor semen and the bacterial species are varied, mainly including gram-positive bacteria. Semen quality is reduced with the increased number of bacterial colonies.