Prevalence of rectal Mycoplasma genitalium and macrolide resistance in men who have sex with men attending Sydney Sexual Health Centre

Background: Sexually transmissible infections (STIs) have been increasing in men who have sex with men (MSM) in recent years; however, few studies have investigated the prevalence or antimicrobial resistance in rectal Mycoplasma genitalium in this group. This study aimed to determine the prevalence and predictors of rectal M. genitalium in MSM attending an urban sexual health service in Sydney, Australia, namely the Sydney Sexual Health Centre (SSHC), as well as estimate the rate of macrolide resistance. Methods: A prospective cross-sectional analysis was conducted of rectally asymptomatic MSM having a rectal swab collected as part of their routine care. Participants self-collected a rectal swab to be tested for M. genitalium and completed a 14-item questionnaire that provided information on behavioural risk factors. The prevalence of rectal M. genitalium was determined and multivariate analysis was performed to assess the associations for this infection. Positive specimens then underwent testing for macrolide-resistant mutations (MRMs) using the ResistancePlus MG assay (SpeeDx, Eveleigh, NSW, Australia). Results: In all, 742 patients were consecutively enrolled in the study. The median age was 31 years (interquartile range 27-39 years), with 43.0% born in Australia. Overall, 19.0% of men were bisexual, 22.9% were taking pre-exposure prophylaxis (PrEP) and 4.3% were HIV positive. The prevalence of rectal M. genitalium was 7.0% (95% confidence interval (CI) 5.3-9.1) overall and 11.8% in those taking PrEP. On multivariate analysis, PrEP use was significantly associated with having rectal M. genitalium (odds ratio 2.01; 95% CI 1.09-3.73; P = 0.01). MRMs were detected in 75.0% (36/48; 95% CI 60.4-86.4%) of infections. Conclusion: Rates of rectal M. genitalium infection were high among asymptomatic MSM attending SSHC and MRMs were detected in 75% of infections. PrEP use was found to be significantly associated with rectal M. genitalium infection. These data contribute to the evidence base for screening guidelines in MSM.