The publication of national treatment guidelines does not usually generate headlines in national newspapers. However, the recent release of draft management guidelines for Mycoplasma genitalium infection was accompanied by high profile media coverage suggesting that it is the next sexually transmitted “superbug.” So what are the facts behind these headlines, and how concerned should we be?
First isolated in 1981, M genitalium is the smallest known self replicating bacterium. Most infections are probably asymptomatic and have no adverse health outcomes. Nonetheless, evidence that M genitalium is associated with serious genitourinary and reproductive health morbidity is accumulating.
In men, there is an unequivocal association with non-gonococcal urethritis, and it is detected in up to 40% of men with persistent and recurrent urethritis. In women, a recent meta-analysis found significant associations with a range of clinical syndromes and adverse reproductive health outcomes, including cervicitis, postcoital bleeding, pelvic inflammatory disease, preterm birth, and spontaneous abortion, and a weak association with infertility.
The population prevalence of M genitalium infection ranged from 1.3% to 3.9% and was higher in countries with a low development index. In Britain, a probability sample survey estimated a prevalence of around 1.3% in the sexually active British population aged 16-44 years.4 In common with many other sexually transmitted infections (STIs), M genitalium infection rates can be considerably higher in men who have sex with men, sex workers, and people attending STI clinics.
The main concern is M genitalium’s increasing resistance to azithromycin and moxifloxacin, the recommended first and second line treatments in Europe, North America, and Australia, especially in the Asia-Pacific region. For example, single nucleotide polymorphisms in region V of the 23S rRNA gene, which confer macrolide resistance, were found in over 60% of M genitalium specimens from people attending STI clinics in Australia in 2015. Furthermore, selective pressure can lead to the emergence of macrolide resistance after exposure to suboptimal levels of drug.
Importantly, resistance markers are highly correlated with treatment failure, especially when the organism load is high.