Chlamydia trachomatis and Neisseria gonorrhoeae bacterial loads in men who have sex with men on pre-exposure prophylaxis: a cross-sectional study

Objective Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are the most commonly reported sexually transmitted infections globally. Anorectal CT/NG detection among men who have sex with men (MSM) and coinfections is common. Epidemiological studies suggest that CT/NG coinfections might result in greater bacterial load and transmissibility than single infection. The purpose of this study was to compare bacterial load and symptoms between CT/NG single and coinfections in MSM. Methods MSM positive for CT or NG on a triple swab (throat, urethra and rectal locations combined) were enrolled. Before treatment, they self-collected anorectal swabs. Bacterial loads for CT/NG were calculated using real-time PCR and compared between single or coinfected individuals, with or without rectal symptoms. Results We enrolled 382 MSM from December 2021 to December 2024. Among all samples: total CT (n=114), total NG (n=125), CT/NG coinfection 29/382 (7.6%). The bacterial loads in single and coinfected samples were comparable. The mean difference between CT alone and CT/NG was 0.40 target copies/mL (95% CI (−0.09 to 0.89), p value=0.107). The mean difference for NG alone and CT/NG was 0.24 copies/mL (95% CI (−0.49 to 0.99), p value=0.498). Among 382 MSM, 15.4% (n=59/382) experienced anorectal symptoms. There was no statistical difference in bacterial burdens between symptomatic and asymptomatic (CT difference of the means 0.52 copies/mL, 95% CI (−0.51 to 1.55); p value=0.313) (NG difference of the means 0.63, CI (0.01 to 1.28); p value=0.05). Conclusions In contrast to prior research, we found similar bacterial burdens in anorectal MSM samples with single CT/NG versus coinfection. Further research is needed to understand the clinical implications of CT/NG coinfections. Future studies should investigate factors influencing anorectal CT/NG bacterial burden, transmissibility and susceptibility, including the function of pre-exposure prophylaxis and the rectal microbiota.