Antimicrobial activity of human cervical mucus.

The antibacterial activity of human cervical mucus (CM) was examined on standardized microbial colonized agar plates (agar diffusion test). In parallel, the lysozyme content of CM was determined by means of a turbidimetric test system in aliquots of the same CM specimens. Suspensions of living lyophilized Micrococcus lysedeikticus were used as bacterial substrate. Testing was performed in a total of 133 CM samples, obtained at mid-cycle from sexually active women from unselected infertile couples with a median age of 30 (range 21-42) years. All mucus specimens showed considerable antibacterial activity with clearly visible circular inhibition zones around the CM-filled holes in the colonized agar plates. Related to the effect of hen's egg white (HEW)-lysozyme on the same plates, the median activity of the CM specimens in the agar diffusion test was equivalent to 33.0 (range 6.4-391.4) microg/ml HEW-lysozyme. However, there was a wide inter-individual range of antibacterial effects of cervical secretions. The cervical index did not significantly influence the outcome of either test. The pH of the endocervical CM also was not correlated with the antibacterial effect. Sexual activity leading to the presence of spermatozoa in CM considerably increased its antibacterial effect. The activity was markedly higher in samples obtained within hours after intercourse compared with those taken after sexual abstinence of >/=5 days (P < 0.05). In microbially colonized CM specimens compared to sterile CM, all obtained under hormonally standardized conditions, the antibacterial activity in the agar plate test was significantly lower (P < 0.05). The results of this pilot study demonstrate the considerable antibacterial activity of human CM.