Mycoplasma genitalium, often shortened to MG, is not a household name. But it should be. It’s a sexually transmitted infection that’s more common than many realise, and it’s becoming harder to treat.

Most people who carry MG have no idea they’re infected. It often causes no symptoms at all. But it can lead to serious problems, especially if left undiagnosed. And it’s often missed during routine STI checks.

To make things worse, MG is quietly developing resistance to common antibiotics. That makes early detection and the right treatment more important than ever.

What Is Mycoplasma Genitalium?

Mycoplasma genitalium is a tiny bacterium that infects the urinary and reproductive tracts. It was discovered in the 1980s, and for a long time, it flew under the radar.

It spreads through sexual contact, including vaginal, anal, and possibly oral sex. Once it’s in the body, it can cause inflammation in the urethra, cervix, and pelvic area. But the tricky part is that most people don’t feel anything. That means MG can stay in the body for months or even years without being noticed.

When symptoms do show up, they can look like other infections. That makes MG easy to confuse with chlamydia or non-specific urethritis. In many cases, people are treated for the wrong thing, and MG remains untreated in the background.

Why It’s Called the Stealth STI

MG is often called a stealth STI because it hides in plain sight. Most people who carry it have no symptoms. Even when symptoms do appear, they’re usually mild or mistaken for something else.

This makes MG easy to overlook, both by individuals and healthcare providers. Unlike chlamydia or gonorrhoea, MG is not included in routine STI screening. You have to specifically ask for it, and in many places, the test isn’t even available.

The infection can quietly cause long-term problems. In men, it may lead to persistent urethritis. In women, it can cause cervicitis or pelvic inflammatory disease, which may affect fertility if left untreated.

The combination of no symptoms, no routine testing, and growing antibiotic resistance makes MG a difficult infection to track and control. That’s why it’s often described as one of the most overlooked threats in sexual health.

How It Spreads

Mycoplasma genitalium spreads through sexual contact. That includes vaginal, anal, and possibly oral sex. It can pass between people even when there are no symptoms.

Like many STIs, MG is more likely to spread when people have multiple partners, unprotected sex, or inconsistent condom use. It doesn’t take much as even a single encounter with an infected person can be enough.

MG is also easy to confuse with other infections. Someone may be treated for chlamydia or another STI without knowing they actually have MG. In some cases, the antibiotics used for other infections don’t work well against MG. That allows it to stay in the body and continue spreading.

Unlike some other infections, there’s no vaccine for MG. Prevention comes down to safer sex practices, communication with partners, and regular testing. especially if symptoms appear or partners test positive for other STIs.

Symptoms in Men and Women

Most people with Mycoplasma genitalium don’t show symptoms at all. That’s part of what makes it so difficult to control. But when symptoms do appear, they can vary depending on sex and the part of the body affected.

In Men

• Pain or burning when passing urine
• Watery or mucus-like discharge from the penis
• Itching or discomfort inside the urethra
• Persistent symptoms after being treated for other STIs

In Women

• Abnormal vaginal discharge
• Pain during sex
• Bleeding between periods or after sex
• Pelvic pain or cramping

If untreated, MG can lead to pelvic inflammatory disease (PID) in women. PID can cause long-term damage to the reproductive system and increase the risk of infertility. In men, ongoing urethritis can cause discomfort and frustration, especially if treatment fails.

There’s also some evidence that MG may increase the risk of acquiring or transmitting HIV, especially when there’s inflammation or damage to the genital lining.

Diagnosis: Why It’s Tricky

Mycoplasma genitalium is hard to detect. Standard STI tests usually don’t include it. In fact, unless your doctor specifically suspects MG, it might not be tested for at all.

The bacteria grow very slowly and don’t show up well in traditional lab cultures. That’s why most clinics rely on nucleic acid amplification tests (NAATs) to detect it. These tests look for the DNA of the bacteria, not the bacteria itself.

NAATs are accurate, but not always available. In Singapore and many other places, testing for MG is only offered in specialised clinics or under specific circumstances — usually when symptoms persist after treatment for other STIs.

If you’ve been treated for chlamydia or urethritis and the symptoms haven’t gone away, MG might be the reason. That’s when it makes sense to ask about testing.

Shim Clinic offers STI testing with a focus on discreet, doctor-led consultations. If symptoms persist or you’re unsure what’s going on, don’t assume it’s been ruled out.

Treatment: Why Resistance Is a Problem

In the past, Mycoplasma genitalium responded well to antibiotics like azithromycin and doxycycline. But that’s changing. MG is quickly developing resistance, especially to azithromycin, which used to be a first-choice treatment.

This makes it harder to treat. Some patients take a full course of antibiotics, only to find their symptoms return. Others may not improve at all.

Because of this, treatment often involves a two-step approach. Doctors may start with doxycycline to reduce the bacterial load, followed by a different antibiotic such as moxifloxacin, which is more effective against resistant strains. But moxifloxacin is a strong medication and may not be suitable for everyone.

This is why test-and-treat strategies are important. Ideally, the lab checks the bacteria for resistance markers before prescribing medication. But in many places, including Singapore, resistance testing is not widely available yet. That means doctors often have to guess and hope the antibiotic works.

Incomplete or incorrect treatment adds to the problem. The bacteria that survive can become harder to kill next time. That’s why you should never take leftover antibiotics or self-medicate based on online advice.

How It Compares to Other STIs

MG vs Chlamydia

Mycoplasma genitalium and chlamydia often cause similar symptoms. Both can lead to pain during urination, discharge, and pelvic discomfort. In women, both may cause cervicitis or pelvic inflammatory disease.

But MG is harder to detect and harder to treat. Chlamydia responds well to standard antibiotics like azithromycin or doxycycline. MG is often resistant to those medications. That means people treated for chlamydia might still have MG without knowing it.

MG vs Gonorrhoea

Gonorrhoea is usually more aggressive than MG. Symptoms tend to appear sooner and are often more noticeable. Gonorrhoea can also lead to serious complications, but it’s easier to test for and more widely recognised.

Both infections can cause urethritis and discharge in men, and pelvic pain in women. But gonorrhoea is part of standard STI screening. MG is not. That makes it easier to miss and more likely to become a long-term issue.

Is MG Incurable?

MG is not incurable, but it’s becoming harder to manage. Treatment still works in many cases, but antibiotic resistance is growing. That’s why test-guided treatment and follow-up testing are so important.

Unlike viral STIs like herpes or HIV, MG is bacterial and can be cleared with the right medication. The challenge is getting the right diagnosis and using antibiotics correctly.

How to Protect Yourself

There’s no vaccine for Mycoplasma genitalium, but there are practical steps you can take to lower your risk.

• Use condoms consistently. They reduce the risk of MG and other STIs, even when there are no symptoms.
• Talk openly with your partners. If someone has had persistent STI symptoms or recently tested positive for another infection, it’s worth discussing MG.
• Get tested if symptoms don’t go away. If you’ve been treated for something like chlamydia or urethritis and the symptoms return, ask your doctor if MG might be the cause.
• Stick to prescribed treatments. Avoid taking leftover antibiotics or starting medication without medical advice. This increases the chance of resistance.

If you’re not sure where to start, Shim Clinic offers judgement-free consultations and STI testing. You don’t need to know exactly what’s wrong to get help.

What to Do If You Think You Have It

If you’ve had symptoms that don’t go away after treatment, or a partner has tested positive for MG, don’t wait it out. This isn’t an infection that clears on its own.

Ask your doctor directly about Mycoplasma genitalium. If testing is available, it may involve a urine sample or a swab from the urethra or cervix. If it’s not available, your doctor may refer you to a clinic that can help.

Follow the full course of antibiotics if prescribed. Don’t stop early, even if you feel better. And don’t reuse old prescriptions. If symptoms persist after treatment, go back for a follow-up.

It’s also important to let your sexual partners know. They may need to get tested or treated too. MG spreads easily and often without symptoms, so they might not realise they’re carrying it.

The sooner you act, the easier it is to clear the infection and stop it from spreading further.