Mycoplasma Genitalium (MGen): The Facts
By Kelley Quinn, M.Ed. | April 23, 2025
When it comes to sexually transmitted infections (STIs), most people are familiar with common bacterial infections such as chlamydia, gonorrhea, and syphilis. However, there’s a bacterial STI that has been around for decades but is less well known — Mycoplasma genitalium (MGen). It can be difficult to detect and treat, making awareness important for both prevention and care.
A Hidden Threat Since 1981
MGen was first discovered in 1981, yet it remains one of the lesser-known STIs. Despite its low profile, MGen is emerging as a significant public health concern.
During a conversation with Dr. Erik Munson, associate professor and STI researcher at Marquette University, he stated “Of the non-ulcer STDs, MGen is the one we see the most [in Milwaukee].” It appears clinically similar to both Chlamydia and Gonorrhea and, partly due to being misdiagnosed and mistreated, has developed antibiotic resistance.
The Risks: More Than Just an Infection
MGen isn’t just another minor infection—it carries some serious risks. Research shows that it’s significantly associated with:
- A twofold increase in the risk for cervicitis (inflammation of the cervix).
- Higher chances of adverse pregnancy outcomes.
- Increased likelihood of PID, which can lead to chronic pelvic pain, infertility, and ectopic pregnancy.
- A greater risk of acquiring or transmitting HIV, particularly among women (assigned female at birth) who are not on antiretroviral therapy.
Why is MGen So Hard to Treat?
Unlike other bacterial STIs, MGen doesn’t have a cell wall, which makes many standard antibiotics ineffective. Treatment is further complicated by rising antibiotic resistance. Here’s what we know so far:
- Doxycycline, often used as a first-line antibiotic, is only about 30-45% effective in treating MGen, but resistance has not shown to be increasing.
- Azithromycin, another common STI treatment, has faced increasing resistance.
- Moxifloxacin is the current go-to option when other treatments fail, but experts caution against overuse to prevent further resistance.
What Can You Do?
While MGen may not be a household name (yet), awareness is the first step in addressing this STI. Here’s how we can prevent the transmission of MGen:
- Use protection
- MGen is contracted through vaginal or anal sex. Condoms and other barrier methods, like dental dams, can reduce the risk of transmission.
- Get tested regularly, even if you don’t have symptoms
- MGen presents predominantly asymptomatic (having no symptoms), frequently for those assigned female at birth. Be sure to ask your healthcare provider if they offer a MGen test, as it is not part of a standard STI panel.
- Common symptoms include unusual discharge, pelvic pain, or discomfort during sexual intercourse. Be sure to talk to a healthcare provider to walk through next steps if these symptoms are present.
- Order an at-home or lab test online. If the test comes back positive, order or schedule a follow-up test after completing treatment to confirm the infection has cleared. Check out the resources at the bottom of this article for more information about at home testing.
- Complete your treatment: If diagnosed, follow your doctor’s instructions carefully and completely to avoid contributing to antibiotic resistance. Due to how difficult MGen can be to treat, make sure to ask for a test of cure at the end of your treatment to confirm that the infection has cleared.
- Advocate for better testing: If you're a clinician, advocate for the availability of MGen tests at your facility. Increased availability of FDA-approved MGen testing could be a game-changer for public health and decrease the prevalence of MGen.
The Bottom Line
MGen may not have the name recognition of chlamydia or gonorrhea, but its impact on reproductive health can be just as serious. As cases continue to rise, staying informed and proactive is the best way to stay ahead of this often-overlooked STI.
Learn More about MGen and Other STIs
ETR’s STD/STI materials deliver the basic facts people need to know about prevention, testing and treatment. View our materials in the ETR Store.
Discussing STI prevention with young people can be difficult. Adapt these skills from HIV motivational interviewing to include in your next lesson plan, featured in our blog with Physician’s Weekly.
Order an At Home STI Test (accurate as of 4/23/2025)
CallOnDoc (provides tests and treatment)
Kelley Quinn, M.Ed. (she/her) is the Youth Engagement and Training Specialist at ETR. Her role involves working with a variety of youth engagement projects as well as training educators in sexual and reproductive health curricula. Kelley’s professional interests are in challenging STI stigma and fostering consent education.
