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

OBJECTIVE: To evaluate whether cervical mucus plugs are antibacterial in vi tro. STUDY DESIGN: Cervical mucus plugs from 56 healthy women in labor were stud ied 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 bact eria, and (2) determination of the antibacterial property of the cervical m ucus plug material by radial diffusion assay with group B Streptococcus and Escherichia coli. RESULTS: In the agar overlay assay, there was complete inhibition of clinic al isolates of Staphylococcus saprophyticus, E coli, and Pseudomonas aerugi nosa and patient-variable partial-to-complete inhibition of Enterococcus fa ecium, Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus, ag alactiae. In the radial diffusion assay, cervical mucus plugs had activity toward group B Streptococcus equivalent to 0.075 mug/mL of gentamicin and t oward E coli equivalent to 0.5 mug/mL of gentamicin. CONCLUSION: A low-molecular substance with antibacterial activity in the ce rvical mucus plug may protect the fetus against ascending infections.