Figure 6. Supportive and inhibitory interactions between N. gonorrhoeae and H₂O₂-producing lactobacilli.

The microenvironment of the female lower genital tract is a complex milieu that is affected by the metabolic by-products of commensal flora. Commensal flora may also form part of the innate defense via the production of bacteriocins and competition for nutrients and colonization receptors. Potential inhibitory factors that are produced by lactobacilli, the predominant flora of the healthy female genital tract, are shown below the dotted line. Factors that may reduce N. gonorrhoeae colonization include biosurfactants, steric hindrance, direct toxicity through the action of H₂O₂, bacteriocins, and low pH. These inhibitory aspects of lactobacilli may be balanced by one or more factors that could support gonococcal growth or survival, which are illustrated below the dotted line. Positive factors include the production of lactate, which in the presence of glucose, increases gonococcal metabolism [44] and resistance to the bactericidal activity of normal human serum [25, 35], nitrite, which the gonococcus can use as an electron acceptor for anaerobic growth [46], and increased iron solubility via a reduction in pH. Lactobacilli may also play an immunoprotective role via modulation of the host response [47].