Yes, Mycoplasma genitalium (often shortened to M. gen or Mgen) is a sexually transmitted infection. It spreads through vaginal and anal sexual contact and is recognized by the CDC as an STI with its own section in the national STI Treatment Guidelines. With an estimated 3.3 million infections among Americans aged 14 to 59 at any given time, it is roughly as common as chlamydia, yet far less well known.
How Common Is Mgen?
National survey data from the CDC puts the prevalence of urogenital Mgen at about 1.7% of the U.S. population aged 14 to 59, with nearly identical rates in males (1.8%) and females (1.7%). That translates to somewhere between 2 and 5 million people carrying the infection at any point in time. For comparison, urogenital chlamydia prevalence is estimated at 1.7% and trichomoniasis at 2.1% in the same population. Mgen is less common than lifelong viral infections like herpes simplex type 2, which affects roughly 12% of the same age group.
How It Spreads
Mgen passes from one person to another during vaginal or anal sex. Because many carriers have no symptoms, the infection often spreads without either partner realizing it. Condom use reduces transmission, but no barrier method eliminates risk entirely. The bacterium infects the urethra in men and the cervix or vagina in women, establishing itself in the mucous membranes of the genital tract.
Symptoms in Men and Women
Most people with Mgen notice nothing at all. When symptoms do appear, they tend to be mild and easy to confuse with other infections.
In men, the most common sign is a discharge from the penis, sometimes accompanied by a burning sensation while urinating. This presentation looks a lot like chlamydia or nongonococcal urethritis, which is why Mgen often goes unrecognized until standard treatments for those infections fail to clear the problem.
In women, symptoms typically involve abnormal vaginal discharge or burning during urination. Some women develop cervicitis (inflammation of the cervix) or pain during sex. Again, these overlap heavily with chlamydia and other common infections, making clinical diagnosis without a specific lab test unreliable.
Why It Matters: Complications
Left untreated, Mgen can cause real harm, particularly in women. A large meta-analysis found that Mgen roughly doubles the risk of cervicitis, pelvic inflammatory disease (PID), preterm delivery, and spontaneous miscarriage. In one U.S. PID treatment trial, 15% of women enrolled were infected with Mgen, and the infection was independently linked to endometritis, an inflammation of the uterine lining.
Subclinical PID, the kind that causes damage without obvious symptoms, is a particular concern. Among women at an urban STD clinic who did not have acute PID, about 51% of those carrying Mgen showed signs of subclinical PID on closer examination. Even after accounting for chlamydia, gonorrhea, and bacterial vaginosis, Mgen independently more than doubled the odds of this silent inflammation.
The link to infertility is still being refined, but the data trends in a worrying direction. When researchers controlled for chlamydia and gonorrhea, women with a history of Mgen had roughly 3.3 times the odds of tubal factor infertility. Lab studies have also shown that Mgen damages the hair-like structures (cilia) lining the fallopian tubes, though the damage appears more moderate than what chlamydia or gonorrhea cause.
In men, persistent or recurrent urethritis is the main complication. Untreated infection can keep cycling through periods of mild symptoms and apparent resolution without ever fully clearing.
How It’s Diagnosed
Mgen is detected through a nucleic acid amplification test (NAAT), which identifies the bacterium’s genetic material. The FDA has cleared this test for use with urine samples, urethral swabs, vaginal swabs, and cervical swabs. A simple urine sample or self-collected vaginal swab is sufficient for most people.
One important caveat: routine screening for Mgen is not currently recommended for people without symptoms. The CDC advises testing in specific situations, primarily when urethritis in men or cervicitis in women keeps coming back after standard treatment, and for women being evaluated for PID. If testing isn’t available locally, clinicians are advised to suspect Mgen whenever urethritis or cervicitis persists or recurs despite appropriate antibiotics for chlamydia and gonorrhea.
Not every clinic or lab offers Mgen testing yet, which is one reason the infection flies under the radar. If you have symptoms that aren’t resolving with treatment, it’s worth asking specifically whether Mgen testing is available.
Treatment Challenges
Mgen is curable with antibiotics, but treatment is more complicated than for most STIs. The bacterium has developed significant resistance to the antibiotics most commonly used for similar infections. Standard single-dose treatments that work well for chlamydia often fail against Mgen, and using the wrong antibiotic can actually drive further resistance.
For this reason, the CDC recommends resistance-guided therapy whenever possible. This means the lab not only detects the bacterium but also checks whether it carries genetic mutations that make it resistant to certain drug classes. Your provider then selects the antibiotic most likely to work based on that specific result. When resistance testing isn’t available, treatment follows a stepwise approach, starting with one class of antibiotic and switching if symptoms persist.
A test of cure, typically performed a few weeks after finishing treatment, is important to confirm the infection has actually cleared. Reinfection from an untreated partner is also a real possibility, so sexual partners generally need to be evaluated and treated as well.
How Mgen Compares to Other STIs
Mgen occupies a middle ground in the STI landscape. It’s as prevalent as chlamydia but far less frequently tested for. It causes many of the same complications as chlamydia and gonorrhea, including PID and potential fertility problems, but it’s harder to treat because of growing antibiotic resistance. And unlike herpes or HIV, it is fully curable once identified and treated with the right antibiotic.
The biggest practical difference is awareness. Chlamydia and gonorrhea are part of routine STI screening panels. Mgen is not. That means it often gets caught only after someone has failed treatment for another presumed infection, or after complications have already developed. If you’re dealing with persistent genital symptoms that haven’t responded to standard STI treatment, Mgen is worth investigating.