Treating Mycoplasma genitalium urethritis in primary care

Guest posting: Dr Nathan Ryder, Clinical Director Sexual Health, Hunter New England Local Health District. 

Mycoplasma genitalium is an emerging sexually transmitted pathogen. While testing is now widely available in Australia, treatment is becoming increasingly complex. M. genitalium resistance is increasing rapidly and a small but significant proportion of cases are currently untreatable. The benefit of treatment in averting long term adverse outcomes is unknown. It is important to restrict the use of moxifloxacin to laboratory-proven infection and avoid asymptomatic screening.

Who to test?

M. genitalium testing is recommended only in people with clinical features of disease, i.e. male urethritis and female pelvic inflammatory disease. Testing asymptomatic people as part of a “sexual health check-up” is NOT recommended, both due to the unknown individual and public health benefit, and the lack of effective and accessible treatment options.  [Testing is done by NAAT (nucleic acid amplification -PCR) of a swab or first pass urine samples].

How to treat?

The Australian STI Guidelines currently have extremely limited recommendations regarding M. genitalium treatment.  The following recommendations are based on Australian data, locally available medications and expert opinion:

Initial treatment of non-gonococcal urethritis:

  • Azithromycin 1 gram oral

Treatment of persistent or recurrent urethritis with laboratory confirmed Mgenitalium infection following azithromycin failure:

  • Moxifloxacin 400mg once daily oral for 10 days (non-PBS prescription; approximate cost to patient A$150)

NOTE: in the absence of ongoing symptoms it is reasonable not to treat M. genitalium infection however later recurrence of symptoms is common.

Treatment of laboratory-confirmed persistent M. genitalium infection following moxifloxacin failure:

  • Doxycycline 100mg twice daily oral for 14 days

Treatment of laboratory confirmed persistent Mgenitalium infection following failure of azithromycin, moxifloxacin and doxycycline treatment and ongoing symptoms:

  • Specialist referral for assessment and consideration of pristinomycin 1g 4 times daily oral for 14 days (non-TGA approved medication requiring a Special Assess Scheme application)

Treatment of ongoing sexual partners: 

  • Give same treatment as the index case
  • Do not test and treat past sexual partners as the benefit of treatment outside of preventing reinfection in current unknown

Test of cure?

Most guidelines recommend a test of cure 4 weeks post-treatment to confirm eradication of infection. However, given the limited treatment options and lack of evidence for adverse health outcomes, HNE Sexual Health does not currently perform a test of cure for urethritis. We do perform a test of cure for pelvic inflammatory disease due to the potentially greater significance of infection in this circumstance.

Background

Antimicrobial resistance in M. genitalium is increasing globally. Australia data from 2016 in Melbourne found 72% of infections to have macrolide (i.e. azithromycin) resistance mutations with 12-15% of cases failing moxifloxacin treatment as well. Whilst earlier observational data suggested a multi-day course of azithromycin was both more effective and delayed the development of resistance, a recent RCT did not find any benefit over the standard 1 gram single dose.

Moxifloxacin treatment failure was found to be more likely following recent azithromycin exposure and in those with higher organism loads, such as symptomatic cases. Due to this, it would be reasonable to use moxifloxacin first line in confirmed cases able to afford it. For the same reasons, using doxycycline 100mg twice daily for 7-10 days for non-gonococcal urethritis (instead of azithromycin) is now becoming increasingly recommended, although not as yet in Australian guidelines.

While only limited data is available regarding pristinomycin there have been many case reports of treatment failure, as had been our experience in Hunter New England. For patients failing pristinomycin, treatment the options are limited and uncertain. One case report demonstrated success with an older drug, spectinomcyin, however this agent requires prolonged daily intramuscular administration and is unavailable in Australia at present. Current research is focused on identifying synergistic antibiotic combinations and implementing individualised treatment based on molecular resistance assay results.

Reference

Image credit: Wikipedia

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