Short answer
Mycoplasma genitalium, often shortened to Mgen or M. genitalium, is an STI that can be involved in persistent or recurrent urethritis, recurrent cervicitis, and some pelvic inflammatory disease questions. CDC does not recommend routine Mgen screening for people without symptoms. Testing is most useful when it is tied to a symptom pattern, the right sample type, resistance-aware treatment, and partner follow-up.
The usual test is a nucleic acid amplification test, or NAAT, rather than culture. A "full STI panel" may not include Mgen, and a positive result should not be treated casually because macrolide resistance and treatment sequencing matter.
When Mgen testing may come up
| Situation | Why Mgen may be discussed | What to clarify first |
|---|---|---|
| Persistent or recurrent urethritis | CDC recommends M. genitalium testing for men with recurrent nongonococcal urethritis. | Were chlamydia, gonorrhea, trichomoniasis, HSV, syphilis, and noninfectious causes considered where relevant? |
| Recurrent cervicitis | CDC says women with recurrent cervicitis should be tested for M. genitalium. | Were BV, yeast, trichomoniasis, chlamydia, gonorrhea, pregnancy, and pelvic symptoms evaluated? |
| Pelvic inflammatory disease | CDC says M. genitalium testing should be considered among women with PID, while evidence about directing PID treatment remains limited. | Is the PID plan already following urgent clinical guidance, and is follow-up arranged? |
| Ongoing symptoms after negative STI tests | Mgen can be missed when a panel only checks chlamydia, gonorrhea, HIV, syphilis, hepatitis, and sometimes trichomoniasis. | Which infections, body sites, and sample types were actually tested? |
| No symptoms | CDC does not recommend screening asymptomatic women or men for M. genitalium. | What specific symptom, positive partner result, or clinical question would this test answer? |
What test is used
CDC says M. genitalium culture can take months and is not practical for routine care. Testing is usually done with an FDA-cleared NAAT. CDC describes FDA-cleared NAAT use with urine and urethral, penile meatal, endocervical, and vaginal swab samples.
Sample type matters. The Aptima M. genitalium assay package insert lists clinician-collected and self-collected vaginal swabs in a clinical setting, clinician-collected endocervical swabs, female and male urine, clinician-collected male urethral swabs, and self-collected penile meatal swabs in a clinical setting. FDA's nucleic-acid-based test list also includes multiple cleared molecular tests that detect Mycoplasma genitalium alone or as part of STI molecular panels.
Why it is not routine screening
Mgen can be asymptomatic, but CDC does not recommend screening asymptomatic people or extragenital testing for M. genitalium. The issue is not that Mgen is unimportant. It is that testing can trigger treatment decisions where resistance, side effects, partner management, and follow-up are more complicated than a simple positive-or-negative panel result.
That is why this test is often a second-step question: "I still have urethral burning," "my cervicitis keeps recurring," "my discharge workup was negative," or "my partner tested positive," rather than "add every possible STI to a routine screen."
Resistance changes the plan
CDC says macrolide resistance markers are common in M. genitalium in the United States and several other regions, and treatment with azithromycin alone can select for resistance. CDC says resistance-guided therapy is preferred when resistance testing is available. When resistance testing is not available, treatment decisions still need a clinician because the regimen and follow-up depend on the situation.
Do not try to self-treat Mgen from a lab result, borrow antibiotics, or reuse old prescriptions. A positive result should come with a plan for treatment, side effects and drug interactions, partner steps, symptom follow-up, and whether a test of cure is needed.
Partner and follow-up questions
CDC notes that partners of people with symptomatic M. genitalium infection can be tested, and those who test positive can be treated. If partner testing is not possible, CDC says the antimicrobial regimen used for the patient can be provided to the partner. The practical question is whether partner testing, treatment, abstaining from sex, or repeat testing is needed to avoid reinfection.
Test-of-cure is not automatic for everyone. CDC says test of cure is not recommended for asymptomatic people who received a recommended regimen, but follow-up changes when symptoms persist, an alternative regimen is used, resistance testing was not available, or a clinician is worried about treatment failure or reinfection.
What a result cannot prove
- It usually cannot prove when infection was acquired or which partner transmitted it.
- A negative Mgen test does not explain every cause of pelvic pain, discharge, burning, urinary symptoms, or urethral irritation.
- A positive result does not replace testing for chlamydia, gonorrhea, trichomoniasis, BV, HIV, syphilis, hepatitis, herpes, UTI, or pregnancy when relevant.
- A urine-only or at-home panel may not use the same sample types, FDA-cleared claims, resistance testing, or follow-up process as a clinic.
- Persistent symptoms after treatment are not always proof that the same infection remains.
Questions to ask before testing
- Am I being evaluated for persistent urethritis, recurrent cervicitis, PID, a positive partner result, or something else?
- Is this an FDA-cleared M. genitalium NAAT?
- Which sample type is best for my anatomy and symptoms: urine, vaginal swab, endocervical swab, urethral swab, or penile meatal swab?
- Is macrolide resistance testing available?
- If the result is positive, who will prescribe treatment and handle side-effect or interaction questions?
- Do recent partners need testing, treatment, or both?
- Do I need a test of cure, symptom follow-up, or repeat testing to check reinfection?
FAQ
Is Mycoplasma genitalium included in a full STI panel?
Usually no. Mycoplasma genitalium testing is not recommended as routine screening for asymptomatic people. CDC recommends targeted testing in specific persistent or recurrent symptom situations.
What test is used for Mycoplasma genitalium?
CDC says culture is impractical for routine care. M. genitalium is usually detected with an FDA-cleared nucleic acid amplification test, or NAAT, using approved urine or swab sample types.
When should Mgen testing be considered?
CDC recommends M. genitalium testing for men with recurrent nongonococcal urethritis and for women with recurrent cervicitis. Testing should also be considered in some PID situations.
Why does antibiotic resistance matter for Mgen?
CDC says macrolide resistance is common and that resistance-guided therapy is preferred when available. A positive result should be managed by a clinician rather than self-treated from a lab report.
Do partners need testing or treatment for Mgen?
CDC notes that sex partners of people with symptomatic M. genitalium infection can be tested, and partners who test positive can be treated. If partner testing is not possible, partner treatment may be considered using the same regimen used for the patient.
Is a test of cure always needed after Mgen treatment?
Not always. CDC says test of cure is not recommended for asymptomatic people who received a recommended regimen, but follow-up changes when symptoms persist, alternative regimens are used, resistance testing is unavailable, or a clinician is concerned about treatment failure or reinfection.