Association of bactericidal activity of genital tract secretions with Escherichia coli colonization in pregnancy

OBJECTIVE: Genital tract secretions exhibit bactericidal activity against Escherichia coli. We hypothesized that this defense may be modulated during pregnancy. STUDY DESIGN: Secretions were collected by vaginal swab from 70 pregnant women (35-37 weeks' gestation) and 35 nonpregnant controls. We mixed E coli with swab eluants or control buffer and colonies enumerated to measure bactericidal activity. Cytokines, chemokines, and antimicrobial peptides were quantified by multiplex or enzyme-linked immunosorbent assay. RESULTS: Pregnant women had significantly greater bactericidal activity, higher concentrations of proinflammatory cytokines, and lower levels of beta defensins compared to controls. Seven (10%) pregnant and 8 (23%) nonpregnant women were vaginally colonized with E coli; colonization was inversely associated with bactericidal activity. CONCLUSION: The soluble mucosal immune environment is altered in pregnancy. We speculate that the observed changes may protect against colonization and ascending infection and could provide a biomarker to identify pregnant women at risk for infectious complications including preterm birth.