Mycoplasma genitalium: the little-known STI that resists antibiotics

What is Mycoplasma genitalium?

Mycoplasma genitalium (often MG) is a small bacterium passed on during sex. It’s less well known than chlamydia or gonorrhoea, but it is one of the causes of urethritis (inflammation of the tube in the penis) and can also affect the rectum.

What are the symptoms?

Most infected people have no symptoms. When they do:

• discharge from the penis, often slight;
• burning when peeing;
• pelvic or testicular pain;
• rarely, anal discomfort.

These signs look like gonorrhoea or chlamydia. When both are negative but symptoms persist, the doctor considers MG.

Why isn’t it routinely tested?

Because MG has developed high antibiotic resistance (macrolides, fluoroquinolones). Treating everyone, including symptom-free carriers, would speed up that resistance. The French National Authority for Health (HAS) therefore revised its guidance in April 2025: according to the French health insurance, PCR testing for MG is only done:

• with symptoms of urethritis (or cervicitis in women);
• with recurrent or persistent symptoms;
• for current partners of an infected person;
• to check for cure, only if symptoms persist 3 weeks after the end of treatment.

Treating symptom-free carriers is no longer recommended, except for partners of a symptomatic patient who tested positive.

How is it treated?

With antibiotics, chosen where possible according to the resistance detected by the lab. Treatment can be longer and more complicated than for other STIs. Never take antibiotics on your own: an ill-suited treatment breeds resistance.

How to prevent it?

• Condoms during penetration;
• see a doctor quickly if you have discharge or burning, and avoid sex until diagnosed;
• tell partners if infection is confirmed.

Note: doxyPEP is not designed to prevent MG.