An in vitro study of antibacterial properties of the cervical mucus plug in pregnancy

OBJECTIVE: To evaluate whether cervical mucus plugs are antibacterial in vitro. STUDY DESIGN: Cervical mucus plugs from 56 healthy women in labor were studied by 2 different antimicrobial assays: (1) analysis of the inhibition by the cervical mucus plug of several gram-positive and gramnegative bacteria by overlaying the cervical mucus plug onto an agar plate with imbedded bacteria, and (2) determination of the antibacterial property of the cervical mucus plug material by radial diffusion assay with group B Streptococcus and Escherichia coli. RESULTS: In the agar overlay assay, there was complete inhibition of clinical isolates of Staphylococcus saprophyticus, E coli, and Pseudomonas aeruginosa and patient-variable partial-to-complete inhibition of Enterococcus faecium, Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus, agalactiae. In the radial diffusion assay, cervical mucus plugs had activity toward group B Streptococcus equivalent to 0.075 mug/mL of gentamicin and toward E coli equivalent to 0.5 mug/mL of gentamicin. CONCLUSION: A low-molecular substance with antibacterial activity in the cervical mucus plug may protect the fetus against ascending infections.