The differential susceptibility of gonococcal opacity variants to sex hormones

Neisseria gonorrhoeae exist in transparent (Tr) and opaque (Op) colony forms. Op forms are recovered from patients early in the menstrual cycle; Tr colonies predominate late in the cycle. The mechanism for this colonial variation was examined by determining the influence of gonodal hormones on growth inhibition of Op and Tr isogenic variants of gonococci. The estrogens, estrone and estradiol, enhanced growth whereas 19-nortestosterone, testosterone, and progesterone significantly inhibited gonococcal growth. Testosterone and progesterone inhibited growth of the Op variants to a greater degree than the Tr variants. Mixture of Tr and Op colonies grown in the presence of progesterone became predominantly Tr, as occurs in the luteal phase of the menstrual cycle. This study supports the hypothesis of hormonal influence on colonial variation but employed artificial in vitro conditions and high hormone levels.