Background Chlamydia trachomatis infection increases above gonorrhoea and syphilis, ranking first among the STDs. Molecular epidemiological researches have shown the predominant genotypes vary between regions, periods and population subgroups. However, serovars E, D and F are the most prevalent serovars. It is unclear whether the epidemiological characteristics were contributed to geography or pathogenicity. We explored the pathogenic diversity of different C. trachomatis serovars in mouse genital infection.

Methods One hundred of female BALB/C mice were divided into serovar E, F, H, J and K groups. The mice in study group treated by medroxyprogesterone acetate were inoculated 10⁷ C. trachomatis into genital tract. C. trachomatis was detected by culture, direct immunofluorescence assay (DFA) and PCR in the cervicovaginal secretion. On the days 7 and 35 after inoculation, inflammation of the cervix, uterus and oviduct were examined by HE stain, and expressions of cHSP60 and CPAF in the uterus and fallopian tube were detected by ELISA.

Results The inflammatory of the cervical mucosa was more severe in serovar E group compared with J, K and H groups on day 7 post-inoculation. Accordingly, cHSP60 and CPAF expression increased significantly in E group compared with other experimental and control groups. On day 35 post-inoculation, the histo-pathological changes of the genital tract were obvious in J, K and H groups, characterised with uterine swelling, pyometra and effusion, fallopian expansion, hydrops, fibrosis and stenosis. cHSP60 and CPAF expression in H group was superior to that in other groups. Positive correlation between cHSP60 and CPAF expression was present on day 7 and 35 post-inoculation, respectively.

Conclusion There existed pathogenic diversity among different C. trachomatis servoars in mouse genital infection. The expression of inflammatory cytokines of cHSP60 and CPAF during Chlamydial infection might partially explain the pathogenic mechanism and the stage of the Chlamidal infection.