Gallegos G et al. (2008) Sperm DNA fragmentation in infertile men with genitourinary infection by Chlamydia trachomatis and Mycoplasma. Fertil Steril 90: 328–334

Chlamydia trachomatis is a major cause of infertility, but the exact mechanism of its effect on sperm has been unclear. Now, a Spanish study has found that the sperm of men infected with C. trachomatis have increased levels of DNA fragmentation.

Gallegos et al. compared sperm from 143 infertile patients infected with C. trachomatis (all of whom were also positive for Mycoplasma infection) with sperm from 50 fertile control individuals. Although sperm motility, concentration and morphology were significantly worse in patients than in controls, these characteristics were within the WHO-defined normal range for most patients—73% were normozoospermic by WHO criteria. However, analysis of sperm DNA showed that a mean of 35% of sperm cells had fragmented DNA in the patient group, compared with 11% in the control group. After a mean of 3.8 months of antibiotic and anti-inflammatory treatment in a subgroup of 95 patients, the mean frequency of sperm with DNA fragmentation decreased from 38% to 24%. Of other sperm characteristics, only morphology showed an improvement.

Of 16 couples who attempted conception during antibiotic treatment, 12.5% were successful; however, of 14 couples who attempted pregnancy 3–6 months after therapy, 84.7% were successful. The mean percentage of sperm with DNA fragmentation was significantly lower in the second group (32% vs 43% of cells).

The authors conclude that C. trachomatis and Mycoplasma infection adversely affects fertility by increasing sperm DNA fragmentation. Antibiotic therapy reduces this damage and can restore fertility in the individuals affected.