Antimicrobial factors in the cervical mucus plug.

OBJECTIVE

The cervical mucus plug is positioned between the microbe-rich vagina and the normally sterile uterine cavity, which suggests a host defense function, but few relevant data are available. We analyzed the composition and antimicrobial activity of cervical mucus plugs.

STUDY DESIGN

Cervical mucus plugs were collected from healthy women at delivery. Groups of plugs were randomly selected for electrolyte analysis, antimicrobial activity assays against group B Streptococcus, Escherichia coli, Candida albicans, and assays of known antimicrobial polypeptides.

RESULTS

Both intact cervical mucus plugs and their aqueous extracts exhibited antimicrobial activity against aerobic microbes, in the order of potency: group B Streptococcus > E coli > C albicans. Semiquantitative Western blotting of extracts showed that secretory leukoprotease inhibitor, lysozyme, lactoferrin, and neutrophil defensins were present at concentrations that were sufficient for antimicrobial activity.

CONCLUSION

The cervical mucus plug is not only a mechanical but also a chemical barrier to infection that ascends from the vagina.