Prevalence of rectal Trichomonas vaginalis and Mycoplasma genitalium in male patients at the San Francisco STD clinic, 2005-2006.

SEXUALLY TRANSMITTED INFECTIONS (STI), such as Chlamydia trachomatis, Neisseria gonorrhoeae, herpes simplex virus (HSV), and Treponema pallidum are common causes of proctitis among gay men and other men who have sex with men (MSM).1,2 Inflammatory proctitis caused by an STI may increase the susceptibility and infectivity of HIV.3,4 In many cases of proctitis, however, no etiological organism is detected.1 The advent of nucleic acid amplification techniques presents an opportunity to detect organisms previously difficult to isolate from the rectum. Two such organisms, Trichomonas vaginalis and Mycoplasma genitalium, have been implicated in male urethritis, female cervicitis, and endometrial infection.5–11 M. genitalium is a small bacterium that was difficult to identify until the development of the polymerase chain reaction (PCR) technique in 1991.12,13 Though studies have detected M. genitalium from the urethra of MSM,14,15 only one study investigated M. genitalium in the rectum by PCR,16 yet a correlation with rectal symptoms was not reported. Recently, a comparison of multitarget real-time PCR and a transcription-mediated amplification (TMA) research assay found both assays to be highly accurate in the detection of M. genitalium from male urine and female vaginal swabs.17 T. vaginalis is a common curable STI worldwide, causing an estimated 174 million new cases annually.18 Conventional methods for detection include culture or microscopic visualization on vaginal wet preparation; both require live organisms for accuracy and have modest sensitivity. The development of nucleic acid amplification techniques has increased case detection19: in a recent study that investigated accuracy of the T. vaginalis culture, PCR and TMA, both TMA and PCR detected significantly more T. vaginalis infections than culture.20 Identifying the etiological causes of proctitis is important to deliver appropriate treatment and decrease the risk for HIV transmission. This study explored the rectal prevalence of T. vaginalis and M. genitalium in a population of MSM in San Francisco, and examined their role in symptomatic and asymptomatic rectal infection. This was a cross-sectional pilot study of 500 consecutive rectal specimens collected at the San Francisco municipal STD clinic from November 11, 2005 to January 4th, 2006. As per current standard of care, all MSM who reported receptive anal sex within 6 months before their clinic visit were screened for N. gonorrhoeae and C. trachomatis by TMA (Aptima Combo2; Gen-Probe, San Diego), validated by the San Francisco Department of Public Health Laboratory for rectal swabs.21 MSM with rectal symptoms (i.e., rectal pruritus, pain, tenesmus, bleeding, or discharge) were evaluated by anoscopy and tested for N. gonorrhoeae and C. trachomatis by TMA and HSV by PCR.22 Rectal discharge was evaluated by Gram stain on-site, and the diagnosis of proctitis was made by the presence of one or more polymorphonuclear neutrophils per high-powered field. HIV-positive patients are not offered HIV testing; therefore, HIV status was determined either by patient report or the result of HIV testing records at the San Francisco municipal STD clinic. During the time period of the study, initial reactive enzyme immunoassays were tested in duplicate (Vironostika HIV-1 Microelisa; bioMerieux, Durham, NC) and confirmed by Fluorognost HIV-1 IFA (Sanochemia Pharmazeutika, Vienna, Austria). All MSM were routinely screened for syphilis by Venereal Disease Research Laboratory test. All C. trachomatis and N. gonorrhoeae TMA swab specimens were routinely sent to the San Francisco Department of Public Laboratory for testing. For the purpose of this study, aliquots of the remnant rectal specimens were deidentified and sent to The Johns Hopkins University International Sexually Transmitted Diseases Research Laboratory for batched testing by research TMA assays for M. genitalium and T. vaginalis (analyte-specific reagent, GenProbe, San Diego).17,20 The cutoff for a positive reaction was 40,000 relative light units for the M. genitalium assays and 60,000 The authors thank the clinicians at the San Francisco municipal STD clinic, City Clinic, for the collection of all the rectal specimens; Katherine Ahrens for initial data analysis, and Dr. Sally Liska and the San Francisco Public Health Laboratory for storing remnant rectal samples. They also thank Gen-Probe for the kind donation of TMA reagents for detection of M. genitalium and T. vaginalis. Suzanna C. Francis has received a travel grant from Gen-Probe. Charlotte A. Gaydos is a member of the speakers’ bureaus for Gen-Probe and Becton Dickinson. Correspondence: Suzanna Carter Francis, MPH, MS, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT. E-mail: [email protected]. Received for publication September 25, 2007, and accepted March 27, 2008. From the *San Francisco Department of Public Health, STD Prevention and Control, San Francisco, California; †San Francisco Public Health Laboratory, San Francisco, California; and ‡Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, Maryland Sexually Transmitted Diseases, December 2008, Vol. 35, No. 12, p.000–000 DOI: 10.1097/OLQ.0b013e318177ec39 Copyright © 2008, American Sexually Transmitted Diseases Association All rights reserved.