Nonclassical Pathogens as Causative Agents of Proctitis in Men who Have Sex With Men

Background. This study aimed to identify enteric and sexually acquired rectal pathogens, other than chlamydia and gonorrhea, associated with symptomatic proctitis in men who have sex with men (MSM). Methods. Anorectal swab samples were obtained from MSM presenting with rectal symptoms and a clinical diagnosis of proctitis at the Melbourne Sexual Health Centre between January 2017 and March 2019. Samples that tested positive for Neisseria gonorrhoeae and Chlamydia trachomatis were excluded. As a comparison group, anorectal samples were also obtained from MSM not reporting symptoms of proctitis between November 2018 and February 2019. Samples from both groups were tested for 15 viral, bacterial, and protozoal enteric pathogens using polymerase chain reaction. Results. Anorectal samples from 499 men with symptomatic proctitis and 506 asymptomatic men were analyzed. Age, HIV status, and pre-exposure prophylaxis (PrEP) use did not differ between men with proctitis and asymptomatic men. Treponema pallidum was more common in men with proctitis (risk difference [RD], 3.6%; 95% CI, 2.0%-5.2%). Most men with anorectal T. pallidum presented with painful anal primary infections. Shigella spp. was more common among men with proctitis compared with asymptomatic men (RD, 1.8%; 95% CI, 0.1%-3.5%). Most men with Shigella did not report diarrhea. Mycoplasma genitalium was more common in men with proctitis (RD, 4.3%; 95% CI, 1.1%-7.5%). Herpes simplex virus (HSV)-1 (RD, 10.1%; 95% CI, 6.8%-13.3%) and HSV-2 (RD, 7.2%; 95% CI, 4.5%-10.0%) were more common with proctitis. Conclusions. Testing for T. pallidum, Shigella, and HSV should be considered in MSM presenting with symptomatic proctitis. These data provide support for M. genitalium as a significant cause of proctitis. A comprehensive diagnostic evaluation is required for MSM with proctitis.