Mycoplasma genitalium

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 in women, and rectal infection which is often asymtpomatic. It is associated with pelvic inflammatory disease (PID) and is a possible cause of preterm delivery, spontaneous abortion and tubal factor infertility.

Screening asymptomatic individuals for Mg is not recommended. A growing number of laboratories offer NAAT testing for Mg and those that do not, can forward specimens to reference laboratories, such as the Molecular Microbiology Laboratory of the Royal Women’s Hospital or the Victorian Infectious Diseases Reference laboratory (VIDRL). Some NAAT tests will also detect a mutation conferring resistance to macrolides such as azithromycin.


In men, a first void urine specimen appears more sensitive than a urethral swab. A urine specimen for M. genitalium should be performed in all men with non-gonococcal urethritis (NGU). See MSHC treatment guideline on urethritis.

In women, vaginal swabs are ideal but first void urine or cervical swabs also can be used. Women who present with clinically apparent cervicitis or PID should be tested for M. genitalium. See MSHC treatment guideline on vaginal discharge.

Men who report sex with men
Men who have sex with men (MSM) who present with symptoms of proctitis should be tested for rectal M. genitalium using an anal swab. See MSHC treatment guideline on proctitis.

Asymptomatic people
Sexual contacts of M.genitalium should be tested and this should include anorectal swabs in MSM. Throat swabs are not necessary. Screening of asymptomatic individuals for M. genitalium is not recommended.


Infections known to be susceptible to azithromycin will develop resistance in 10 – 20% of cases treated with azithromycin. By December 2016, Mg infections diagnosed at Melbourne Sexual Health Centre (MSHC) had macrolide resistance mutations detected in approximately 80% of MSM and 50% of heterosexual men. Data on women will be added when available, but are probably similar to heterosexual men.

Because resistance is common and there are few effective treatment options, MSHC is using an experimental treatment protocol supported by limited data. This includes antibiotics that are not on the PBS. We are using doxycycline rather than azithromycin for NGU, cervicitis and PID and we recall patients infected with Mg for treatment with an antibiotic to which Mg is likely to be susceptible.

MSHC is now routinely pre-treating all Mg infections with one week of doxycycline prior to using a second definitive antibiotic. While doxycycline only cures about 20-30% of Mg infections, preliminary data suggest it lowers the bacterial load in most cases, making Mg more likely to be cured with the second antibiotic.

For Mg infections not known or suspected to be macrolide resistant use

  • doxycycline 100mg bd, 7 days, followed immediately by
  • azithromycin 1g stat, then 500mg daily for another three days (2.5g total)

For Mg infections suspected to be macrolide resistant (Mg in MSM, persisting symptoms >7 days, positive Mg result >21 days after azithromycin, Mg resistance mutation detected) use

  • doxycycline 100mg bd, 7 days, followed immediately by
  • moxifloxacin 400mg daily for seven days

Moxifloxacin is not TGA-approved for this infection and may cause diarrhoea or tendonitis. We recommend discussing this with patients. Pharmacies typically charge over $70 for five tablets. There are limited efficacy data and no data for treatment courses of less than seven days.

Test of cure is essential in managing all Mg infections because of the risk of persisting, asymptomatic, resistant infection. The ideal time is three weeks (minimum two) after starting the definitive second antibiotic. Sometimes a positive Mg result is received after azithromycin has been prescribed as treatment. If symptoms are improving it is reasonable to wait and perform a test of cure. If symptoms have persisted or rebounded to similar intensity, treatment failure is likely and best treated as resistant infection.

If treatment failure occurs, consider reinfection from an untreated partner. Testing and treating partners is recommended, but careful testing (including anorectal 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.

M.genitalium associated PID
Routine PID treatment is not likely to adequately treat Mg-associated PID and moxifloxacin is recommended. See MSHC treatment guideline on PID.

M.genitalium in pregnancy
Azithromycin is category B1 and can be prescribed in pregnancy. If a patient is pregnant and considered at risk of resistant M.genitalium infection this case should be discussed with a sexual health physician and pristinamycin may be recommended.

The content of these treatment guidelines is for information purposes only. The treatment guidelines are generic in character and should be applied to individuals only as deemed appropriate by the treating practitioner on a case by case basis. Alfred Health, through MSHC, does not accept liability to any person for the information or advice (or the use of such information or advice) which is provided through these treatment guidelines. The information contained within these treatment guidelines is provided on the basis that all persons accessing the treatment guidelines undertake responsibility for assessing the relevance and accuracy of the content and its suitability for a particular patient. Responsible use of these guidelines requires that the prescriber is familiar with contraindications and precautions relevant to the various pharmaceutical agents recommended herein.

Last Updated February 2017