Colonization of the respiratory and genital tracts of female mice with Mycoplasma pneumoniae and protection afforded to the genital tract by prior respiratory colonization.

Mycoplasma pneumoniae, strain MY 12763, colonized the throats of 6 BALB/c female mice for at least 18 days after intranasal inoculation. The same strain colonized, in high titre, the vagina of 9 of 10 progesterone-treated BALB/c mice for at least 35 days, but none of 10 oestradiol-treated mice. Mice were less susceptible to genital-tract colonization with the multiple broth-passed FH strain of M. pneumoniae, only 3 of 10 becoming colonized. The 6 mice inoculated intranasally with strain MY 12763 were immune to genital-tract colonization with the same strain, whereas 10 mice without respiratory-tract colonization were susceptible. Protection of the genital tract in this way was at least as effective as that afforded by previous genital-tract colonization. In a further experiment, 26 immunocompetent BALB/c mice colonized previously in the respiratory tract were resistant to vaginal colonization, whereas 20 BALB/c nude mice, similarly colonized in the respiratory tract, were susceptible in the vagina, illustrating the importance of cell-mediated immunity. The possible relevance of the findings to the human situation is discussed.