Quantitative study of Chlamydia trachomatis in genital infection.

Chlamydia trachomatis inclusion counts on inoculated McCoy cell coverslips were used as an index of the degree of infection of the cervix in women and of the urethra in men with urethritis. High inclusion counts were obtained significantly more often from men than from women, from women with cervical ectopy, and from women who had had recent sexual intercourse. Low inclusion counts were significantly more common in men with a past history of gonococcal urethritis. Higher chlamydial isolation rates in women with gonorrhoea and in women taking the contraceptive pill could not be attributed to a greater degree of infection, since inclusion counts were not raised in these patients. There was evidence that strains of C trachomatis might vary in their ability to establish themselves in the genital tract because high counts in men with NGU were associated with high counts in their female consorts and the levels of counts in men were associated with the frequency of chlamydial isolation from their female consorts. The relatively simple technique of inclusion counts in cultures for chlamydia from the genital tract may yield valuable information about the behaviour of different strains of C trachomatis in causing pathological changes, in the transmission of infection between individuals, and in the response to specific chemotherapy.