Introduction There are limited data on the prevalence of M. genitalium and macrolide resistance in asymptomatic MSM. Due to limited availability, testing for M. genitalium has generally been for symptomatic patients, such as men with non-gonococcal urethritis (NGU) and proctitis. Recent data from Melbourne Sexual Health Centre (MSHC) show MSM are over-represented among men with M. genitalium urethritis and that macrolide resistant M. genitalium is almost twice as common among MSM, as among heterosexual men (76% vs 39%). In order to inform practice guidelines we undertook a screening study in asymptomatic MSM, to obtain accurate prevalence and resistance estimates.

Methods One thousand consecutive consenting MSM attending MSHC without symptoms of NGU or proctitis, not known to be contacts of MG, are tested and given a short questionnaire on behavioural risk factors and recent antimicrobial therapy. First pass urine and an anorectal swab are tested by polymerase chain reaction (ResistancePlus MG test, SpeeDx, Australia) for the presence of M. genitalium and for macrolide resistance mutations (MRM).

Results From 23 August to 15 December 2016, 401/1000 (40%) MSM have been recruited. M. genitalium was detected in 30 of 401 MSM [prevalence 7.5% (95% confidence interval (CI): 5.1%, 10.5%)]; 20 rectal [rectal prevalence 5.0% (95%CI: 3.1%, 7.6%)] and ten urethral infections [urethral prevalence 2.5% (95%CI: 1.2%, 4.5%)]. MRM were detected in 25 of 30 infections [83.3% (95%CI: 65.3%, 94.4%)]. MRM were detected in 18/20 rectal [90% (95%CI: 68.3%, 98.8%)] and 7/10 urethral [70% (95%CI: 34.8%, 93.3%)] infections. Estimates will be updated in June 2017.

Conclusion MSM without urethral and rectal symptoms attending a sexual health centre in Melbourne have a high prevalence of M. genitalium, and over 80% have macrolide resistance mutations. Rectal infections are twice as common as urethral. To our knowledge this study will provide the largest urethral and rectal estimates of M. genitalium infection and macrolide resistance in MSM and will inform future screening guidelines.