Background: It has been hypothesized that CT acquired orally can survive passage through the gastrointestinal tract and establish an infection in the rectum. If and how often this occurs is unknown.
Methods: We enrolled individuals assigned male sex at birth who reported sex with men and denied receptive anal sex (RAS) in the past 2 years or reported RAS 1-2 years ago but were tested and treated since last RAS. Participants enrolled in-person at the Sexual Health Clinic in Seattle, Washington (December 2019-July 2022) or online (July 2021-March 2022). Participants completed a survey that asked about 13 non-RAS behaviors and self-collected rectal swabs for CT nucleic acid amplification testing (NAAT) and CT culture and viability-PCR (vPCR) testing. We identified individuals whose only reported sexual behaviors were those that did not involve direct contact with the rectum but could lead to rectal CT via oral introduction (i.e., “oral-only” behaviors: fellatio, cunnilingus, rimming a partner). We classified NAAT-positive infections as “viable” if either culture or vPCR were positive.
Results: We enrolled 275 men with NAAT results and complete behavioral data; 28 (10%) were rectal CT NAAT-positive. Of 275 men, 60 (22%) reported that their only sexual exposures in the past 12 months were oral-only behaviors. Five (8.3%) of 60 tested positive for rectal CT by NAAT; only 1 had viable CT present in the rectum (culture and vPCR positive). There were an additional 43 individuals who reported behaviors that involved direct contact with the rectum (e.g., been rimmed) 2-12 months ago, but whose only sexual exposures in the past 2 months were oral-only. Of these, 4 (9%) of 43 tested positive for rectal CT by NAAT; 1 had viable CT present in the rectum (culture-negative but vPCR positive). Thus, 9 (32%) of 28 NAAT-positive rectal CT infections were likely acquired via oral inoculation with 22% (2/9) representing viable infections.
Conclusions: Passage of CT from the oropharynx to the rectum occurs but appears to most often be nucleic acid remnants rather than viable bacteria. Nonetheless, it appears possible to establish a culturable rectal CT infection via oral inoculation.
