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.