Mycoplasma genitalium

Mycoplasma genitalium

Infection: Mycoplasma genitalium infection; M gen

Brief description:
  • A non-culturable bacteria that can cause sexually transmitted infection.
  • Often carried asymptomatically, but can cause urethritis, cervicitis and possibly PID.
  • Not well known, but likely more common than gonorrhoea, less common than chlamydia.
  • The availability of testing varies between regions – check with your local laboratory.
Did you know?

Significance in many situations still not well understood.

  • Asymptomatic anorectal colonisation is common in men who have sex with men (MSM).
  • Uncertain whether causes proctitis or epididymo-orchitis in men.
Who should I test?

Second line investigation in people where chlamydia and gonorrhoea have been excluded / already treated, and have:

  • Recurrent or persistent urethritis that has not resolved with doxycycline treatment for non-gonococcal urethritis.
  • Cervicitis or PID that has not responded to standard treatment.

Treatment can be complicated.

  • Commonly resistant to first line treatment (azithromycin).
  • Discussion with a Sexual Health physician or microbiologist recommended prior to testing for this reason (many laboratories will decline testing without this).
Test of choice:

Request M. genitalium NAAT

NAAT on a vaginal swab (self- or clinician-collected) or endocervical swab. The Aptima system can be used; chlamydia and gonorrhoea NAAT can be performed on same swab.

  • Excellent sensitivity – a negative test on a well-collected sample makes the diagnosis very unlikely
  • Excellent specificity – a positive test reliably detects the organism, but doesn’t necessarily imply it is the cause of symptoms
  • First void urine is second line in women due to lower sensitivity.

NAAT on first void urine or urethral swab are the only accepted samples in men.

  • Similar sensitivity and specificity to above.
Tests to avoid/specialist tests:
  • Outside the context of contact tracing, avoid testing in asymptomatic people, including anorectal testing in MSM, as asymptomatic carriage is common and of uncertain significance.
  • Detection in the oropharynx/throat is very uncommon, so oropharyngeal swabs are not accepted.
Other considerations:

Many laboratories will test for macrolide (azithromycin) resistance +/- fluoroquinolone resistance when testing for M. genitalium. Interpretation and management of results can be complex and should be in conjunction with a Sexual Health physician.