Mycoplasma genitalium: The Overlooked Sexually Transmitted Infection Affecting Millions Worldwide

By Stephanie Nwakaegho, Gentechnews Health Columnist

Sexually transmitted infections (STIs) remain a major public health concern worldwide. While infections such as HIV, gonorrhea, syphilis, and chlamydia receive significant attention, another sexually transmitted pathogen has been quietly spreading for decades with far less public awareness: Mycoplasma genitalium (Mgen).

Every year, millions of people are tested for sexually transmitted infections, receive an “all clear,” and walk away with a false sense of security. What many of them do not know is that the test they were given may not have looked for one of the most prevalent bacterial STIs in the world.

Mycoplasma genitalium (Mgen) does not appear on standard STI panels in most countries. It rarely announces itself with dramatic symptoms. Yet it is quietly present in bodies across the globe, causing inflammation, reproductive damage, and long-term complications while remaining almost entirely invisible to the people it infects.

This bacteria was first isolated in 1981 and formally named as a new bacterial species in 1983, Mgen as it is commonly called is now recognised by the U.S. Centers for Disease Control and Prevention (CDC) as a common sexually transmitted infection and one of the most treatment-challenging bacterial pathogens in sexual health medicine. In some regions, the antibiotics once used to treat it now fail in the majority of cases.

What Is Mycoplasma genitalium? Causes, Transmission, and Why It Is Hard to Treat

Mycoplasma genitalium is among the smallest self-replicating bacteria ever discovered. Unlike most bacteria, it lacks a cell wall entirely, and that structural absence is clinically significant: entire categories of antibiotics, including penicillins and cephalosporins, work by attacking bacterial cell walls, because this bacteria lacks cell wall, these antibiotics are useless against Mgen. This leaves clinicians with a narrow pharmacological toolkit, and the bacteria have been steadily exploiting that limitation.

The infection targets the urinary and reproductive tracts and spreads through sexual contact, often without producing any symptoms in the person carrying it. The CDC estimates that approximately 1 to 2% of the general adult population globally is infected at any given time. That figure climbs considerably in higher-risk groups, where studies at sexual health clinics have documented prevalence rates ranging from 5% to over 26%. In some populations, Mgen may now be more common than gonorrhoea.

Mycoplasma genitalium Worldwide: Prevalence, Antibiotic Resistance, and Public Health Impact

Mgen is one of the leading causes of non-gonococcal urethritis in men, and it is strongly associated with cervicitis and pelvic inflammatory disease in women. Controlling it is complicated by one core challenge: the majority of infected individuals experience no symptoms. They feel perfectly well while unknowingly transmitting the bacterium to partners, sometimes for months or years at a time.

The Antibiotic Resistance Crisis

The most alarming development surrounding Mgen is how rapidly it has developed resistance to antibiotics. According to the CDC, macrolide resistance, with macrolides being the antibiotic class previously used as first-line treatment, now ranges from 44% to 90% across the United States, Canada, Western Europe, and Australia. In Vietnam, over 61% of tested Mgen samples carried resistance mutations. In Japan, macrolide resistance has been detected in nearly 90% of isolates.

More troubling still: treating Mgen with a single standard dose of azithromycin without resistance testing does not simply fail in resistant cases. It can generate resistance in 10 to 12% of previously susceptible infections. This is how an uninformed prescription can transform a treatable infection into a harder-to-treat one, which can then be passed onward. As a result, self-medication is not merely ineffective; it is a public health risk.

Mgen and HIV

Studies have found that Mycoplasma genitalium infection is associated with an increased risk of HIV acquisition. Researchers believe the inflammation caused by the infection may make it easier for HIV to establish itself in exposed individuals.

Among people living with HIV who are not receiving antiretroviral therapy, Mgen infection has also been associated with higher levels of HIV in genital secretions, potentially increasing the risk of onward transmission. In communities where both infections circulate, this interaction may have significant public health consequences.

Pregnancy Complications

A 2024 study published in the peer-reviewed journal Med found that Mgen infection during pregnancy was significantly associated with lower infant birth weight, with co-infections producing even greater reductions. Other research has linked Mgen to increased risks of preterm birth and spontaneous abortion. Among HIV-positive pregnant women studied in Kenya, 21.4% were found to carry Mgen, and those infected had measurably higher HIV viral loads than those who were Mgen-negative.

Mycoplasma genitalium in Nigeria

In Nigeria, Mycoplasma genitalium exists in enforced obscurity. It is present, it is spreading, and for the vast majority of people it infects, it will never be detected.

A landmark 2022 study at Caleb University in Lagos, the first in Nigeria to use advanced phylogenetic molecular analysis to identify Mgen in the general population, found the infection in sexually active female students. What was perhaps more striking than the detection itself was this: zero awareness. Not low awareness, but none. Among educated, sexually active young adults, knowledge of Mycoplasma genitalium was essentially nonexistent.

The study identified several factors associated with infection, including multiple sexual partners, previous STI history, and inconsistent condom use. These findings mirror risk factors observed internationally.

Across West Africa, a multi-country study spanning Burkina Faso, Côte d’Ivoire, Mali, and Togo found significant Mgen burden in men who have sex with men, while noting that antibiotic resistance data for the African region remains critically scarce. West African female sex workers have been found to carry Mgen at rates as high as 26%. Nigeria, with its enormous population and constrained diagnostic infrastructure, almost certainly reflects or exceeds these patterns. The true burden of the infection here is not just unknown; it is unknowable under current conditions.

How Is Mycoplasma Genitalium Spread? Risk Factors and Transmission Routes

Mycoplasma genitalium is transmitted through sexual contact. Transmission can occur through unprotected vaginal or anal sex, genital-to-genital contact, and contact with infected genital secretions.

A person can be infected by a partner who has no symptoms and no knowledge of their infection. The absence of symptoms does not mean the absence of risk.

Risk increases substantially with multiple or concurrent sexual partners, inconsistent condom use, a prior history of sexually transmitted infections, and HIV co-infection. Rectal infections have also been documented and, like genital infections, are frequently asymptomatic.

Mycoplasma genitalium Symptoms in Men: What to Watch For

Most men carrying Mgen will not know they have it. When symptoms do occur, they typically involve the urethra and may include:

Burning or pain during urination

A watery or clear discharge from the penis

Persistent irritation inside the urethra

Urethritis that recurs or fails to resolve with standard antibiotic treatment

A man who has been treated for urethritis, improved briefly, and then relapsed should consider whether Mgen was never adequately addressed. Research shows it accounts for a substantial proportion of persistent, treatment-resistant urethritis cases.

Rectal infections are also documented in 1 to 26% of men who have sex with men and are frequently without symptoms.

Mycoplasma genitalium Symptoms in Women: Why Most Cases Go Unnoticed

In women, Mgen is even more invisible. Most infected women experience no symptoms at all.

When symptoms develop, they closely resemble those of chlamydia or gonorrhoea, making clinical distinction without laboratory testing essentially impossible. Possible symptoms include:

Abnormal vaginal discharge

Burning during urination

Pain during sexual intercourse

Bleeding after sex

Bleeding between menstrual periods

Lower abdominal or pelvic pain

Many women experiencing these symptoms will be assessed and treated for other conditions without improvement, cycling through consultations over months before Mgen is ever considered. In the meantime, untreated infection may travel upward through the reproductive tract, contributing to cervicitis and, in more serious cases, pelvic inflammatory disease.

Health Complications of Untreated Mycoplasma genitalium Infection

Untreated Mgen can cause lasting harm in both men and women.

In Men

Complications may include:

Chronic urethritis resistant to standard treatment

Persistent urinary discomfort and genital inflammation

Possible contribution to epididymitis, an inflammation of the tube connecting the testicle to the vas deferens

In Women

The consequences can be more serious: cervicitis, pelvic inflammatory disease, increased risk of ectopic pregnancy, adverse pregnancy outcomes including preterm birth and lower infant birthweight, and increased susceptibility to HIV acquisition.

The connection between Mgen and female infertility is an area of active research. The infection is thought to damage the fallopian tubes through persistent, low-grade inflammation, even in women who have never noticed a symptom. It is important to be precise here: while case-control studies and meta-analyses suggest a significant association between Mgen and infertility, evidence on causation versus association remains suggestive rather than conclusive. Research is ongoing, and the full extent of Mgen’s reproductive impact in women is still being established.

What is not in question is that untreated infection can cause harm. Early diagnosis and treatment are far preferable to managing complications after they occur.

Why Mycoplasma genitalium Is Rarely Diagnosed and What Gets Overlooked

Mycoplasma genitalium has earned the label “hidden STI” for reasons rooted in both biology and circumstance.

Biologically, most infected people feel completely well. Even those who develop symptoms often experience them as mild and intermittent: brief discomfort that seems to come and go, easily dismissed or confused with a urinary tract infection.

By circumstance, Mgen is excluded from standard STI screening panels in most countries, including Nigeria. A person can request a full STI screen, receive comprehensive testing, and be told everything is fine while Mgen remains undetected and untreated.

Clinical reports document cases of patients spending months, and sometimes years, seeking answers for persistent urinary or pelvic symptoms before Mycoplasma genitalium is finally identified as the underlying cause.

Unfortunately, A standard STI test does not screen for Mycoplasma genitalium. If you want to be tested for it, you must specifically ask.

How Is Mycoplasma Genitalium Diagnosed?

The only reliable diagnostic method is the Nucleic Acid Amplification Test (NAAT), which detects the actual DNA of the bacterium in a patient sample. It is the global gold standard.

In 2019, the U.S. Food and Drug Administration approved the first commercial NAAT specifically for Mgen, the Aptima assay, significantly expanding diagnostic capability in countries with access to it.

Samples can be collected from:

Urine

Vaginal swabs

Cervical swabs

Urethral swabs

Rectal swabs

Traditional bacterial culture is not practical. Mgen grows so slowly that culturing it from a clinical specimen can take months.

Where available, resistance testing alongside NAAT is the ideal approach since knowing whether a strain is macrolide-resistant before treatment begins is often the difference between a successful cure and a cycle of failed prescriptions.

Testing is particularly warranted for individuals with persistent or recurrent urethritis, recurrent cervicitis, pelvic inflammatory disease that has not responded to standard treatment, or ongoing symptoms despite treatment for other STIs.

Mycoplasma genitalium Treatment: Why Standard Antibiotics Often Fail

Mycoplasma genitalium is treatable, but treatment has become one of the more nuanced challenges in sexual health medicine.

Current CDC guidelines recommend a two-stage, resistance-guided approach.

Stage One: Doxycycline (7 Days)

This does not eradicate the infection but significantly reduces the bacterial load, making the second antibiotic far more effective and reducing the risk of further resistance developing.

Stage Two: Treatment Based on Resistance Results

For macrolide-susceptible strains, high-dose azithromycin is used.

For macrolide-resistant strains, moxifloxacin (400 mg daily for seven days) is the recommended alternative.

When followed correctly, this approach achieves cure rates exceeding 90 to 95%, as demonstrated by Australian data, where resistance-guided therapy was pioneered.

Fluoroquinolone resistance, which affects moxifloxacin, is also beginning to emerge in parts of Asia. Researchers are actively investigating alternative antibiotics, including sitafloxacin and pristinamycin, for cases where current options fail.

A test of cure, consisting of a repeat NAAT performed two to four weeks after treatment, is recommended to confirm clearance, particularly where resistance testing was unavailable.

Why You Should Never Self-Medicate for Mycoplasma genitalium

In many countries, including Nigeria, antibiotics can sometimes be obtained without proper medical supervision. While it may be tempting to self-treat symptoms such as burning during urination or unusual discharge, doing so can be harmful.

Mycoplasma genitalium is not treated in the same way as many other bacterial infections. Taking the wrong antibiotic, the wrong dose, or an incomplete course can contribute to antibiotic resistance and make future treatment significantly more difficult.

Only a qualified healthcare professional should determine:

Whether testing is appropriate

Whether treatment is necessary

Which antibiotic regimen should be used

The correct dosage and duration

Whether follow-up testing is required

Whether sexual partners should also be evaluated and treated

If diagnosed, informing recent sexual partners is essential. Reinfection from an untreated partner is one of the most common reasons treatment appears to fail.

How to Prevent Mycoplasma genitalium: Evidence-Based Strategies

Preventing Mycoplasma genitalium relies on many of the same strategies used to prevent other sexually transmitted infections.

1. Use Condoms Consistently and Correctly

Condoms significantly reduce the risk of transmission during vaginal and anal sex.

2. Reduce the Number of Concurrent Sexual Partners

Fewer sexual partners generally means fewer opportunities for exposure.

3. Get Tested Regularly and Ask Specifically About Mgen

Do not assume a standard STI panel includes Mycoplasma genitalium. Ask your healthcare provider whether testing is available and appropriate for you.

4. Do Not Ignore Persistent Symptoms

Unusual discharge, burning during urination, pelvic pain, or unexplained bleeding should prompt medical evaluation.

5. Notify and Involve Sexual Partners

Partner notification helps prevent reinfection and limits ongoing transmission within the community.

6. Avoid Sexual Activity During Treatment

Sexual activity should be avoided until treatment is completed, clearance is confirmed, and partners have been evaluated.

7. Seek a Full Sexual Health Review

Given the documented links between Mgen and HIV, a confirmed diagnosis should prompt broader sexual health assessment, including HIV testing where appropriate.

Nurse’s Insight

Mycoplasma genitalium has benefited enormously from being overlooked. It has spread quietly, developed resistance to the drugs meant to stop it, and accumulated consequences in people who never knew it was there.

The tools to address it exist: accurate NAAT diagnosis, resistance-guided treatment, partner notification, condom use, and informed sexual health care. What is needed now is the awareness to demand those tools, the healthcare systems willing to provide them, and communities informed enough to understand why they matter.

In Nigeria and across sub-Saharan Africa, where diagnostic access remains limited and public awareness is near zero, that work is particularly urgent.

This infection does not have to stay hidden. It only does so because too few people know to look for it. Now that you’re informed, inform others and protect yourself.

 

Stephanie Nwakaegho, Gentechnews Health Columnist can be reached via thestephanienwakaegho@gmail.com