Mycoplasma Genitalium

You can have this infection for months or years without knowing. A large share of women who test positive for Mycoplasma genitalium have no symptoms at all, yet the bacterium is linked to cervicitis, pelvic inflammatory disease, infertility, and adverse pregnancy outcomes.

It is also one of the most commonly missed sexually transmitted infections. Standard STI panels typically check for chlamydia and gonorrhea, not MG (Mycoplasma genitalium), so a clean routine screen does not rule it out. A vaginal swab analyzed by modern molecular testing is the most accurate way to find it.

What This Test Detects

MG is a tiny sexually transmitted bacterium without a cell wall that colonizes the lining of the vagina, cervix, and urethra. It is detected with a nucleic acid amplification test, which looks for fragments of the bacterium's genetic material in a swab sample. The test result is reported as positive or negative.

Vaginal swabs sample the colonized mucosa directly and consistently yield higher bacterial loads than urine. In testing comparisons in women, vaginal swabs detect MG with roughly 97 to 99 percent sensitivity, compared to about 78 to 86 percent for urine. Self-collected vaginal swabs perform about as well as clinician-collected ones.

How Common It Is

Prevalence varies widely by population. In the general population of higher-income countries, MG is found in roughly 1 to 2 percent of women. In high-risk or clinic-based groups, that figure climbs sharply.

Sources: Berdoyes et al. 2026; Schröder et al. 2025; Emerging Infectious Diseases 2015; Seña et al. 2018.

What this means for you: a negative standard STI panel does not equal a negative MG test, because most clinics do not include MG in routine screening. Current CDC guidelines do not recommend routine MG screening of people without symptoms, so testing is generally most useful if you have persistent or recurrent symptoms, pelvic inflammatory disease, or another clear indication. If that describes you, testing is the only way to know your status.

Pelvic Inflammatory Disease and Cervicitis

MG is independently associated with both cervicitis (inflammation of the cervix) and pelvic inflammatory disease, a serious infection of the upper reproductive tract that can scar the fallopian tubes. A meta-analysis pooling multiple studies found that women infected with MG were about 1.7 times as likely to have cervicitis (odds ratio 1.66, 95% CI 1.35 to 2.04) and roughly 2.1 times as likely to have PID (odds ratio 2.14, 95% CI 1.31 to 3.49) compared to uninfected women. A more recent 2024 meta-analysis estimated a somewhat lower pooled odds ratio for PID of about 1.67 (95% CI 1.24 to 2.24).

In US sexual health clinics, MG is detected in roughly 12 to 21 percent of women with cervicitis and about 15 percent of women with PID. Modeling from a UK cohort estimated that about 5 in 100 untreated MG infections in women progress to clinical PID over time.

Infertility and Pregnancy Outcomes

MG has been linked to infertility and adverse pregnancy outcomes. In the same meta-analysis above, MG infection was associated with about 1.9 times higher odds of preterm birth (odds ratio 1.89, 95% CI 1.25 to 2.85) and about 1.8 times higher odds of spontaneous miscarriage (odds ratio 1.82, 95% CI 1.10 to 3.03). For infertility specifically, the pooled estimate showed about 2.4 times higher odds, though the confidence interval crossed 1 (odds ratio 2.43, 95% CI 0.93 to 6.34).

A separate systematic review focused on pregnancy found that, after adjusting for other factors, MG infection in pregnancy was associated with roughly 2.3 times higher odds of preterm birth.

HPV and Cervical Disease

MG often coexists with other sexually transmitted infections and may interact with the human papillomavirus. A meta-analysis found that women with MG had about 1.5 times higher odds of high-risk HPV infection (odds ratio 1.50, 95% CI 1.11 to 2.02). Persistent vaginal MG has been linked to persistent high-risk HPV infection in cohort data, though the direction of causation is still being studied.

HIV Risk

MG infection has been associated with an increased risk of acquiring HIV in observational studies. The bacterium and the disturbed vaginal microbiome that often accompanies it appear to make the genital lining more vulnerable to other infections.

Co-infections and the Vaginal Microbiome

MG frequently travels with other reproductive-tract conditions. It commonly co-occurs with chlamydia, gonorrhea, and bacterial vaginosis. In a study of African-American women, specific BV-associated bacteria and higher levels of Lactobacillus iners (a less protective vaginal bacterium) were both linked to higher MG prevalence.

Recent bacterial vaginosis raised the odds of acquiring a new MG infection by about 3.5 times in a Kenyan cohort. This makes MG testing especially worth considering if you have recurrent BV or unexplained vaginal symptoms.

Why a Single Result Is Not the Whole Story

A single well-collected vaginal swab is highly accurate for diagnosis, but MG itself behaves dynamically. In one prospective study of women undergoing pregnancy termination, about 46 percent cleared MG on their own without treatment over a 3 to 9 week window, with lower starting bacterial load predicting clearance. Other cohorts suggest spontaneous clearance over a period of weeks to a few months.

At the same time, many infections persist or recur, and the bacterium is often macrolide-resistant, meaning the standard first-line antibiotic frequently fails. After any treatment, a test of cure 2 to 4 weeks later is the only way to confirm the infection is gone. If you develop new symptoms or have a new partner, retesting is reasonable, though routine screening of people without symptoms is not currently recommended by US guidelines.

When Results Can Be Misleading

• Specimen quality: vaginal swabs (whether self-collected or clinician-collected) outperform urine for detecting MG in women, with sensitivity around 97 to 99 percent versus 78 to 86 percent for urine. A negative urine test is less reassuring than a negative vaginal swab.
• Recent antibiotics: azithromycin, doxycycline, moxifloxacin, and other antibiotics taken for any reason can suppress or eradicate MG, making a current swab falsely negative even if you were carrying the bacterium recently.
• Menstrual bleeding at the time of sampling: menstrual blood can shift the vaginal microbial mix transiently. Published evidence on whether bleeding actually reduces MG molecular test sensitivity is limited, but collection during heavy bleeding is generally avoided when possible.
• Bacterial load and assay differences: older or laboratory-developed PCR tests can be less sensitive than current commercial assays (Aptima MG, cobas TV/MG). Lower bacterial loads are more likely to be missed by less sensitive methods.

What to Do If You Test Positive

A positive MG result should trigger a few specific next steps. Because macrolide resistance is common (often 30 to 50 percent and in some US cohorts higher), treatment ideally follows a resistance-guided sequence: a course of doxycycline followed by either high-dose azithromycin or moxifloxacin, depending on whether resistance mutations are detected. Cure rates with resistance-guided regimens reach 92 to 95 percent, compared to roughly 41 percent with azithromycin alone in some real-world cohorts. When resistance testing is not available, the CDC's recommended empiric regimen is doxycycline 100 mg twice daily for 7 days followed by moxifloxacin 400 mg daily for 7 days.

You should also be tested for chlamydia, gonorrhea, and trichomoniasis if those were not already part of your panel, since co-infection is common. Your current sexual partner or partners should be tested and treated to prevent reinfection, and condoms or abstinence are advised until both you and any partner have completed therapy and a test of cure 2 to 4 weeks after treatment confirms clearance. If symptoms persist despite treatment, a specialist in sexual health or infectious disease can guide salvage options, such as extended doxycycline or minocycline. (Sitafloxacin is sometimes used in Japan but is not FDA-approved in the United States.)