Mycoplasma genitalium in men who have sex with men (MSM)

Mycoplasma genitalium (Mg) is a sexually transmitted bacterium that is difficult to culture and detection relies on the use of nucleic acid amplification tests (NAAT). It causes urethritis in men, cervicitis and pelvic inflammatory disease in women, and rectal infection which is often asymptomatic. There have been several articles in mainstream media in the last few months regarding Mg as a new "superbug" and as such there has been an anecdotal increase in clients requesting information and testing on Mg (1, 2).

Because evidence-based data is currently limited, resistance is common, and there are few effective treatment options, including antibiotics that are not on the PBS, treatment guidelines are difficult to develop and maintain, and can be inconsistent between locations. It is best to consult your local sexual health service or call NSW SHIL for help with managing Mg.

Melbourne Sexual Health Centre (MSHC) is a world leader in Mg research and here we summarise their current experimental treatment protocol supported by limited data (3). MSHC is able to test for concurrent macrolide resistance and Mg NAAT which supports their current approach to treatment. Until resistance and Mg testing is more widely available and this approach has been assessed, it is difficult to provide specific recommendations for primary care.

Indications for Mg testing in men

There is currently no evidence to support screening of asymptomatic individuals for Mg. However, testing is recommended for the following syndromes and situations:

  1. Urethritis: all men with symptoms of urethral discharge, discomfort and dysuria: first void urine specimen for Mg NAAT.
  2. Proctitis: MSM who present with symptoms of proctitis (e.g. rectal pain, discharge or bleeding) should be tested for rectal Mg NAAT using an anal swab.
  3. Sexual contacts of Mg: should be tested including ano-rectal swabs in MSM. Throat swabs are not indicated as current evidence indicates pharyngeal infection is uncommon.

Treatment and follow up

Current Australian STI management guidelines advise treating uncomplicated Mg infections not known or suspected to be macrolide resistant with azithromycin 1g stat (4).

However, infections known to be susceptible to azithromycin will develop resistance in 10 – 20% of cases treated with azithromycin. A recent MSHC study detected macrolide-resistant mutations in Mg infections in approximately 80% of MSM and 50% of heterosexual men (3).

For Mg infections suspected to be macrolide resistant (Mg in MSM, persisting symptoms greater than7 days after first line treatment, positive Mg result more than 21 days after azithromycin, or Mg resistance mutation detected) MSHC suggest using moxifloxacin 400mg daily orally for seven days.

Moxifloxacin is not TGA-approved for this infection and may cause diarrhoea or tendonitis. It is an option for GPs comfortable prescribing it privately, alternatively refer to your local Sexual Health clinic for further management. Pharmacies typically charge around $90 for seven tablets. There are limited efficacy data and no data for treatment courses of less than seven days.

Test of cure (TOC)

TOC is essential in managing Mg infections because of the risk of persisting, asymptomatic, resistant infection. The ideal time is three weeks after starting antibiotics.

If treatment failure occurs, consider reinfection from an untreated partner. Testing and treating partners is recommended, but careful testing (including ano-rectal swabs in MSM) and observation of the index case may be sufficient. Infection rates in contacts are 40–50% in women and MSM and 30% in heterosexual men.

To reduce azithromycin use and the generation of macrolide resistance in Mg, MSHC is using 7 days oral doxycycline 100mg bd as first line treatment for NGU and proctitis. Patients who test positive to Mg are recalled while on doxycycline and prescribed azithromycin if macrolide susceptible and moxifloxacin if macrolide-resistant.

As information about Mg spreads through the community, you may notice an increase in anxiety in your patients. Remember there are a number of counselling services available for referrals.

There is an urgent need for new national data to bring consistency to Mg guidelines and new effective treatment options to become available.

Article submitted by Victoria Hounsfield, Senior CMO at Clinic 16, Northern Sydney LHD Sexual Health Service


  1. Spooner, R. (2017, February 11). Researchers raise concerns over sexually transmitted superbug. The Sydney Morning Herald. Retrieved from
  2. Up to 400,000 Aussies could be carrying drug resistant STI (2017, February 13). 9News. Retrieved from
  3. Mycoplasma genitalium (2017, February). Retrieved from
  4. Mycoplasma genitalium (2016, May 23). Retrieved from