Mycoplasma Genitalium (Mgen) Testing — The Emerging STI
Content last reviewed 2026-09-12 · Educational information — not medical advice
Quick answer
Mycoplasma genitalium is an emerging STI causing urethritis and cervicitis that mirrors chlamydia presentation but resists first-line antibiotics — NAAT urine/swab testing identifies it, guiding resistance-aware treatment choices.
What is Mycoplasma genitalium?
A tiny bacterium recognized as a genuine STI only in recent decades — it causes a meaningful share of non-gonococcal urethritis in men and cervicitis/PID contributions in women. The problem child: it lacks a cell wall (dodging many antibiotics naturally) AND has acquired macrolide resistance widely, making blind treatment unreliable.
Who should test for Mgen?
CDC recommends testing (not empiric treatment) for: persistent/recurrent urethritis or cervicitis cases where chlamydia/gonorrhea came back negative, and PID cases — precisely because treatment decisions depend on results. Routine screening isn't currently recommended for asymptomatic people.
How does the test work?
NAAT on first-catch urine (men), vaginal/endocervical swabs (women) — same specimen formats as chlamydia testing, often orderable alongside standard panels. Some laboratories add macrolide-resistance marker detection, which directly shapes antibiotic selection.
Treatment complexity
Resistance-aware sequencing: doxycycline priming then moxifloxacin for macrolide-resistant strains, or josamycin where available. This isn't DIY territory — Mgen treatment genuinely benefits from clinician guidance informed by resistance testing, which is the whole point of testing first.
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Frequently asked questions
Is Mgen on standard STD panels?
Usually not — most comprehensive panels cover chlamydia/gonorrhea/HIV/syphilis/hepatitis. Mgen requires specific ordering.
Can Mgen go away without treatment?
Sometimes clears spontaneously over months; symptomatic infections deserve proper treatment rather than waiting games.