Introduction We have used the pigtailed macaque model to individually study chlamydia (bacteria) and trichomonal (parasite) infections. To increase utility of the model, we explored infection potential for both chlamydia and trichomoniasis, when delivered simultaneously to macaques. This co-infection model will be useful for testing the efficacy of developing multi-purpose technologies.

Methods Twelve female Macaca nemestrina were challenged by cervical inoculation with C. trachomatis E (CT: 5E6 IFU in 0.5 mL volume), immediately followed by vaginal exposure to T. vaginalis ATCC 50148 (TV: 5E5 trichomonads in 0.5 mL volume). For five weeks, infection status, chlamydia-specific serum antibody, and tissue responses were followed. Nucleic acid amplification tests were employed to detect each organism; cervical swabs were also cultured for chlamydia detection. Cervicovaginal tissues were monitored by colposcopy. Each animal completed a five day regimen of oral azithromycin plus metronidazole followed by test of clearance.

Results Nine of twelve macaques tested positive for infection with both pathogens on at least three weekly visits. One animal was positive for chlamydial infection only (TV negative) for two weeks. These ten animals developed chlamydial IgG antibody titers of at least 1:16. The two remaining animals had limited, self-clearing infections; CT positive for one week, plus TV positive for one or two weeks. Neither of these macaques developed serum antibody to CT. During five weeks of secretion sampling, chlamydia positivity ranged from 1 to 5 weeks (median 5 weeks) and TV positivity ranged 0–5 weeks (median 5 weeks) as well. Colposcopy revealed blisters on the cervix of three co-infected animals. Neither infection could be correlated to changes in vaginal pH, exudate or polymorphonuclear cell presence.

Conclusion We have demonstrated that co-infection with Chlamydia trachomatis and Trichomonas vaginalis is achievable in the pigtailed macaque model. Infections are individually detectable and concurrent treatments are effective in clearing both organisms.

Disclosure of interest statement This research was supported by NIH Contract HHSN272201000006I, Task Number HHSN27200008 and by the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health through Grant Number P51 OD010425 Washington National Primate Research Centre. No pharmaceutical grants were received in the development of this study.