Prevalence of Mycoplasma genitalium in gay men equals that of chlamydia

The prevalence of Mycoplasma genitalium – an STI that many people have never heard of – among gay and bisexual men is comparable to that of chlamydia, Australian researchers report in Sexually Transmitted Infections.  Pooling the results of 46 international studies showed Mycoplasma genitalium infection rates of 5% in the urethra, 6% in the rectum and 1% in the throat. The prevalence was higher among men with STI symptoms and the rate of urethral infection was higher among HIV-positive men.

“The prevalence of Mycoplasma genitalium in this study was similar to chlamydia prevalence estimates in men who have sex with men, which have been reported in the order of 3.5%-3.7% in the urethra, 5.6% at the rectum and 0.5% at the pharynx,” comment the investigators.

First identified in 1981, Mycoplasma genitalium is a bacterial STI. It can be transmitted via anal, oral and vaginal sex. Urethral infection can cause discharge and pain when urinating and rectal infection can be accompanied by proctitis (inflammation of the rectum). The infection is treated with a variety of antibiotic regimens, including azithromycin, doxycycline and moxifloxacin. However, high rates of antibiotic resistance have been detected. It is important not to resume sexual activity until follow-up tests have confirmed the infection has been cleared.

International STI guidelines make different recommendations concerning Mycoplasma genitalium. Whereas they generally recommend that gay and bisexual men should be routinely screened for infection with gonorrhoea and chlamydia in the urethra, rectum and throat, they do not recommend screening for Mycoplasma genitalium. This is due to a lack of clarity about the natural history of the infection and challenges with treatment due to resistant strains. However, British and Australian guidelines now recommend testing for the infection in men with symptoms such as urethral discharge, pain and proctitis.

Given these inconsistencies, a team of researchers led by Dr Rosie Latimer from the Sexual Centre, Alfred Health, Melbourne, pooled the results of 46 studies in order to determine the prevalence of Mycoplasma genitalium infection in gay men at the urethra, rectum and throat. They also wanted to see if prevalence differed according to the presence of symptoms and HIV infection status.

The included studies involved a minimum of 50 gay men and were conducted between 1981 and 2018.

Most of the studies (42%) were carried out in Europe, 28% were from the Western Pacific region (mainly Australia and China), 26% were from the Americas (mainly the USA) and only one was from Africa.

Urethral prevalence was reported in 34 studies. The overall infection rate was a little under 5% (range = 0% to 26%). Fifteen of these studies reported on symptoms and showed that prevalence was three times higher among symptomatic men compared to men without symptoms (7% vs 2%, p < 0.001). HIV status was reported in 20studies, their results showing that urethral Mycoplasma genitalium infection was twice as high among men with HIV-positive men compared to HIV-negative men (7% vs 3%, p = 0.006).

Prevalence of rectal infection was reported in 25 studies. The overall rate was 5% (range 0% to 30%). Only seven studies reported on symptoms, showing that prevalence was 16% among men with symptoms compared to 8% among asymptomatic men (p = 0.039). HIV status was recorded in eleven studies, showing an infection rate that was slightly higher among HIV-positive men compared to HIV negative men (11% vs 7%).

The rate of infection in the throat was analysed in seven studies. Six of these reported a rate of 0% to 2%, but one study found 13% prevalence. Exclusion of this outlier gave an overall prevalence of 0%. Numbers were too small to compare prevalence according to symptoms or HIV status.

“This meta-analysis provides site-specific estimates for Mycoplasma genitalium in men who have sex with men that…present biologically plausible patterns of infection,” conclude the authors. “These data provide an evidence base to inform testing, and clinical practice, and highlight the need for further research in this population to understand the pathogenic [disease causing] role and natural history of Mycoplasma genitalium in men who have sex with men.”