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Mycoplasma Genitalium 2018


Mycoplasma genitalium was first isolated in 1981, having been cultured from urethral specimens of two men presenting with non-gonococcal urethritis (NGU). M. genitalium belongs to the Mollicutes class, and with a genome of only 580 kilobases in size, is the smallest known self-replicating bacterium.

Although it was initially thought that disease appeared to be limited to the genito-urinary tract, there is some evidence it could potentially cause proctitis. The specialised tip-like structure of M. genitalium enables it to adhere to and invade epithelial cells. Infection may persist for months or years. 

The evidence suggests that the majority of people infected with M. genitalium in the genital tract do not develop disease. M. genitalium infection is unequivocally and strongly associated with NGU. Typically, the prevalence of M. genitalium in men with NGU is 10-20% and in male patients with non-chlamydial non-gonococcal urethritis (NCNGU) is 10-35%.

Several studies support an association of M. genitalium infection in cisgender women with post coital bleeding and cervicitis, endometritis and pelvic inflammatory disease (PID).


Clinical Features

Signs and symptoms in males

  • None – the majority are asymptomatic
  • Urethral discharge
  • Dysuria
  • Penile irritation
  • Urethral discomfort
  • Urethritis (acute, persistent, recurrent)
  • Balanoposthitis (in one study)

Complications in males

  • Sexually acquired reactive arthritis
  • Epididymitis

The clinical presentation of M. genitalium urethritis is similar to other causes and thus clinical features of acute symptomatic NGU cannot be used to determine the infective aetiology.

Signs and symptoms in females

  • None – the majority are asymptomatic
  • Dysuria
  • Post-coital bleeding
  • Painful inter-menstrual bleeding
  • Cervicitis
  • Lower abdominal pain (see Complications: PID)

Complications in females

  • Pelvic inflammatory disease
  • Tubal factor infertility (uncertain association)
  • Sexually acquired reactive arthritis
  • Pre-term delivery

Individuals with cervicitis due to M. genitalium frequently have no symptoms at all. If present, symptoms are nonspecific, with the most common symptom being post-coital bleeding. Clinical signs and symptoms of M. genitalium-associated PID are similar to, and indistinguishable from, PID due to C. trachomatis.



M. genitalium is fastidious and extremely slow growing, thus culture is not useful for diagnosis. Diagnosis should ordinarily be made on NAATs, targeting specific bacterial DNA or RNA targets.

Indications for testing for M. genitalium

Based on symptoms

  • We recommend testing for M. genitalium infection in people with non-gonococcal urethritis (1B)
  • We recommend testing for M. genitalium infection in people with signs and symptoms suggestive of pelvic inflammatory disease (1B)
  • Consider testing for M. genitalium infection in people with signs or symptoms of muco-purulent cervicitis, particularly post-coital bleeding (2B)
  • Consider testing for M. genitalium infection in people with epididymitis (2D)
  • Consider testing for M. genitalium infection in people with sexually-acquired proctitis (2D)

Based on risk factors

  • We recommend testing current sexual partners of persons infected with M. genitalium (1D)


Specimen choice

  • We recommend first void urine as the specimen of choice in cisgender men (1C)
  • We recommend vaginal swabs (clinician- or self-taken) as the specimen of choice in cisgender women (1C)
  • We recommend that where possible, all M. genitalium-positive specimens should be tested for macrolide resistance mediating mutations (1B)



General advice

Patients should be given a detailed explanation of their condition with particular emphasis on the long-term implications for the health of themselves and their partner(s). This should be reinforced with clear and accurate written information. A patient information leaflet for M. genitalium can be found in the PIL section.

Patients should be advised to abstain from sexual intercourse until 14 days after the start of treatment, and until symptoms have resolved. Where azithromycin has been used this is especially important because of its long half-life, and is likely to reduce the risk of selecting/inducing macrolide resistance if the patient is re-exposed to M. genitalium. We recommend a test of cure (TOC) should be performed in all patients.


The duration of treatment with moxifloxacin for uncomplicated infection has been reduced from ten days to seven, pending a revised full guideline due in late 2023. This change in recommendation has arisen due to the comparable efficacy of seven days vs. ten days for treatment of uncomplicated infections due to Mgen, and the reduction in the occurrence of side effects with shorter courses of treatment. A duration of 14 days remains recommended in the treatment of complicated infections.

Treatment of uncomplicated urogenital infection (urethritis, cervicitis)

  • Doxycycline 100mg bd for seven days followed by azithromycin 1g orally as a single dose then 500mg orally once daily for 2 days where organism is known to be macrolide-sensitive or where resistance status is unknown (1D)
  • Moxifloxacin 400mg orally once daily for 7 days if organism known to be macrolide-resistant or where treatment with azithromycin has failed (1B)

Treatment of complicated urogenital infection (PID, epididymo-orchitis)

  • Moxifloxacin 400mg orally once daily for 14 days (1D)


For alternative regimens, please refer to the full guidelines.


Pregnancy and breastfeeding

A three-day course of azithromycin can be used for uncomplicated M. genitalium infection detected in pregnancy. The use of moxifloxacin in pregnancy is contra-indicated. In women with likely macrolide resistance, or with upper genital tract infection in pregnancy, options are limited. Although doxycycline is considered safe for use in the first trimester by the FDA, the BNF advises against its use in all trimesters. There are no data regarding the use of pristinamycin in pregnancy.

Very low levels of azithromycin are detected in breast milk, and systemic exposure in infants does not exceed that observed when azithromycin is administered for treatment, therefore risk is considered to be low. Doxycycline is excreted into breast milk and is contraindicated in nursing mothers due to the risk of tooth discolouration and effects on bone growth. Use of moxifloxacin is contra-indicated during breastfeeding. Pristinamycin is contraindicated during breastfeeding due to its side effect profile.


Partner notification

Only current partner(s) (including non-regular partners where there is likely to be further sexual contact) should be tested and treated if positive. This is to reduce the risk of re-infection to the index patient. Partners should be given the same antibiotic as the index patient unless there is available resistance information to suggest otherwise.


Download the Full Guidelines