Mycoplasma Genitalium (Mgen)

How Mycoplasma genitalium spreads

Mgen spreads through vaginal and anal sex, and possibly through genital-to-genital contact. It is not spread by toilet seats or casual contact. Risk factors include a new partner, multiple partners and not using condoms. Many people carry it without symptoms and can pass it on.

Symptoms

In people with a penis

• burning or pain when urinating
• watery or mucous discharge from the penis
• urethral itching
• less often, epididymitis (testicular pain and swelling) or proctitis with rectal infection

Mgen causes about 15 to 20 percent of non-gonococcal urethritis and up to 40 percent of urethritis that persists or comes back after treatment.

In people with a vagina

• vaginal discharge
• bleeding after sex or between periods
• pain when urinating
• pain during sex
• lower abdominal or pelvic pain

It can cause cervicitis and is linked to pelvic inflammatory disease, which can lead to infertility and ectopic pregnancy. There may also be links to preterm birth.

Diagnosis

Mgen cannot be grown easily in a lab, so it is detected with a nucleic acid amplification test (NAAT):

• first-catch urine sample in men
• vaginal swab (often self-collected) in women
• rectal swab where relevant

Where available, testing for macrolide resistance mutations guides antibiotic choice.

Routine screening of people without symptoms is not currently recommended. Testing is advised for:

• persistent or recurrent urethritis
• persistent or recurrent cervicitis
• pelvic inflammatory disease (consider)
• sexual partners of people with Mgen

Testing for other STIs, including chlamydia, gonorrhea, trichomoniasis, HIV and syphilis, is usually done at the same time.

Treatment

Mgen has become resistant to several antibiotics, especially azithromycin (a macrolide). Current CDC guidance recommends a two-step approach:

1. doxycycline first, to reduce the amount of bacteria
2. then moxifloxacin, or azithromycin if testing shows the strain is macrolide-susceptible

Your clinician will choose the regimen based on resistance testing where available. Pelvic inflammatory disease caused by Mgen may need moxifloxacin-based treatment.

After treatment

• avoid sex until you and your partners have finished treatment and symptoms have gone
• a test of cure about 3 weeks after treatment may be recommended, particularly if symptoms persist
• partners should be tested and treated
• if symptoms persist, see a sexual health specialist; resistant infections may need other antibiotics

Prevention

• use condoms consistently
• limit the number of sexual partners
• get tested with new partners
• ensure partners are treated before resuming sex

Frequently asked questions

What are the symptoms of Mycoplasma genitalium?

Many people have no symptoms. Men may have burning when urinating and a watery discharge. Women may have vaginal discharge, bleeding after sex or between periods, pain when urinating or pelvic pain. Symptoms can resemble chlamydia.

How is Mycoplasma genitalium tested?

It is detected with a nucleic acid amplification test (NAAT) on a urine sample or a vaginal, urethral or rectal swab. Where possible, labs also test for antibiotic resistance, which helps doctors choose the right treatment.

How is Mycoplasma genitalium treated?

The CDC recommends doxycycline first, followed by moxifloxacin, or azithromycin if the strain is not resistant. Partners should also be treated. A test of cure may be advised because resistance is common.

Why is Mycoplasma genitalium hard to treat?

Mgen lacks a cell wall, so many common antibiotics do not work, and it has rapidly developed resistance to azithromycin and, increasingly, to fluoroquinolones such as moxifloxacin. Resistance-guided treatment improves cure rates.

Can Mycoplasma genitalium cause infertility?

In women, Mgen is linked to cervicitis and pelvic inflammatory disease, which can damage the fallopian tubes and contribute to infertility and ectopic pregnancy. The evidence is still developing, but prompt treatment of symptomatic infection is recommended.