Mycoplasma Genitalium (MG): Symptoms, Treatment, and Resistance in Singapore
Mycoplasma genitalium is one of the smallest known bacteria and an increasingly recognised sexually transmitted infection. It causes non-gonococcal urethritis (NGU) in men and cervicitis or pelvic inflammatory disease in women. Most infections are asymptomatic, and antibiotic resistance is now a defining clinical concern.
Medically reviewed by Dr. Qiao Yufei, MD
This guide covers what M. genitalium is, how it spreads (including oral transmission), the symptoms in men and women, the sequential antibiotic regimen used to overcome resistance, and how testing works at Mediway Medical Centre. M. genitalium is one of several conditions covered in our broader STDs in Singapore overview.
What is Mycoplasma genitalium?
Mycoplasma genitalium (often shortened to MG or M. genitalium) is one of the smallest free-living bacteria known. Unlike most bacteria, it lacks a cell wall, which is why beta-lactam antibiotics like penicillin do not work against it. M. genitalium colonises the urogenital tract and causes a sexually transmitted infection that can persist for months or years, often without symptoms.
Although first identified in the 1980s, M. genitalium has only been recognised as a significant STI over the past 20 years, as testing methods improved and antibiotic resistance emerged. Per the US Centers for Disease Control and Prevention (CDC), M. genitalium is now estimated to cause 15 to 25% of NGU cases and a similar share of cervicitis and pelvic inflammatory disease in women.
Yes, but treatment is complex due to high antibiotic resistance. Current first-line therapy is sequential: doxycycline for 7 days, followed by an extended azithromycin course (or moxifloxacin if macrolide resistance is detected). Resistance testing increasingly guides the choice of antibiotic. A test of cure 3 to 4 weeks after treatment is recommended.
How Mycoplasma genitalium spreads
M. genitalium is transmitted through sexual contact with an infected partner. Both symptomatic and asymptomatic carriers can pass on the bacterium.
- Unprotected vaginal sex with an infected partner (the most common route)
- Anal sex with an infected partner; can cause rectal infection
- Oral sex is a possible but less well-established route; some research suggests oral-to-genital transmission is possible
- Vulva-to-vulva contact and shared sex toys without a fresh condom or proper cleaning
Condoms and risk reduction
Condoms reduce M. genitalium transmission risk significantly when used consistently and correctly during vaginal and anal intercourse. They are not 100% protective: skin-to-skin contact outside the condom can still transmit the bacterium in rare cases.
Who is at higher risk?
- People with multiple sexual partners or inconsistent condom use
- Anyone with a previous STI diagnosis, particularly chlamydia (M. genitalium often co-occurs)
- People with persistent or recurrent NGU after standard treatment (often points to M. genitalium)
Signs and symptoms of Mycoplasma genitalium
Most M. genitalium infections are asymptomatic, particularly in women. People can carry the bacterium for months to years without knowing and pass it to partners. When symptoms occur, they overlap with chlamydia and other causes of urethritis or cervicitis.
In men
- Urethral discharge (clear, white, or cloudy)
- Burning or pain on urination
- Urethral irritation or itching
- Symptoms often milder than gonorrhoea
- Many men have no symptoms at all
In women
- Vaginal discharge or bleeding between periods
- Bleeding after sex
- Pelvic or lower abdominal pain
- Pain during intercourse
- Cervicitis on examination (most often asymptomatic)
If you have NGU symptoms that did not clear with standard chlamydia/gonorrhoea treatment, M. genitalium is a strong possibility. Your doctor may add a specific M. genitalium NAAT test and switch antibiotics to doxycycline-followed-by-azithromycin (or moxifloxacin if resistance is suspected).
How Mycoplasma genitalium is diagnosed
M. genitalium cannot be cultured easily in standard labs (it grows very slowly), so diagnosis relies on molecular testing. At Mediway Medical Centre:
- NAAT (nucleic acid amplification testing): the only practical test for M. genitalium. Performed on a first-catch urine sample (men) or vaginal swab (women); can also be done on rectal or pharyngeal swabs where indicated
- Macrolide resistance testing: increasingly available alongside the diagnostic NAAT, this detects mutations in the 23S rRNA gene that predict azithromycin resistance, guiding antibiotic choice
- Co-testing: M. genitalium testing is often performed alongside chlamydia and gonorrhoea NAAT, since they cause similar symptoms and may co-occur
Most NAAT results return within a few working days. Treatment can usually start at the same visit if clinical suspicion is high; the regimen is then adjusted if resistance testing shows azithromycin resistance.
Mycoplasma genitalium treatment
M. genitalium treatment is more complex than other bacterial STIs because of antibiotic resistance. Current CDC and international guidelines recommend a sequential two-step regimen:
Doxycycline (7 days)
Reduces bacterial load and improves the response to step 2. Doxycycline alone has only modest cure rates against M. genitalium, which is why step 2 is added.
Azithromycin extended (4 days)
Used if macrolide resistance testing is negative or unknown. If macrolide resistance is detected, moxifloxacin 400 mg daily for 7 days replaces step 2.
Why antibiotic resistance is the central concern
M. genitalium has rapidly developed resistance to azithromycin (the historical first-line treatment). Per CDC, macrolide resistance rates exceed 50% in some populations. Doxycycline alone has only modest cure rates. This is why current guidelines use sequential therapy and increasingly rely on macrolide resistance testing to select the right antibiotic. Empirical azithromycin monotherapy is no longer recommended.
After treatment
- Sexual partners from the past 60 days should be tested and treated, even if asymptomatic
- Avoid sexual activity until at least 7 days after both partners complete treatment
- Test of cure (repeat NAAT) 3 to 4 weeks after treatment is recommended to confirm clearance, since persistent infection is common
- Persistent or recurrent infection after first-line therapy may need moxifloxacin or specialist input
How to prevent Mycoplasma genitalium
Practise safe sex
- Use condoms consistently and correctly during vaginal, anal, and oral sex
- Use a fresh condom or barrier on shared sex toys between partners
- Limit the number of sexual partners
Get screened regularly
Routine STI screening should include M. genitalium NAAT, particularly if you have persistent or recurrent NGU symptoms after chlamydia/gonorrhoea treatment, or are in a higher-risk group. Test of cure 3 to 4 weeks after treatment is essential because reinfection and persistent infection are both common.
Communicate with your partner
Open conversations about sexual health, recent partners, and STI status help both partners stay safe. If you test positive for M. genitalium, your current partner (and any partner from the past 60 days) should be tested and treated at the same time, even if they have no symptoms.
What happens if Mycoplasma genitalium is left untreated?
Untreated M. genitalium can cause significant complications, particularly in women:
- Persistent or recurrent NGU in men, often resistant to standard antibiotics
- Cervicitis in women: chronic inflammation that may be asymptomatic but causes ongoing infection
- Pelvic inflammatory disease (PID): can damage the fallopian tubes, causing infertility and ectopic pregnancy
- Tubal-factor infertility: emerging evidence links M. genitalium to subfertility in women
- Treatment-resistant infection: untreated infections allow further selection of resistant strains, complicating both individual care and public health
- Onward transmission: untreated carriers continue to pass M. genitalium to partners
All of these are preventable with prompt sequential antibiotic treatment and partner co-treatment, which is why testing and treatment matter even when symptoms feel mild or are absent.
Frequently asked questions
01 What is Mycoplasma genitalium?
Mycoplasma genitalium (M. gen) is a sexually transmitted bacterium that can cause urethritis in men and cervicitis or pelvic inflammation in women. It is one of the smallest known bacteria capable of self-replication. M. genitalium is often asymptomatic, so many people do not know they are infected. The bacterium has notable antibiotic resistance, making timely diagnosis and appropriate treatment important.
02 What are the symptoms of M. genitalium?
Many people with M. genitalium have no symptoms and may carry the bacterium without knowing. When symptoms occur in men, they may include penile discharge, burning during urination, or testicular discomfort (similar to chlamydia). In women, symptoms may include unusual vaginal discharge, painful urination, pain during intercourse, bleeding between periods, or pelvic pain. Testing is needed to distinguish M. genitalium from other STIs with overlapping symptoms.
03 How long after exposure do M. genitalium symptoms appear?
Symptoms, when they occur, may appear days to weeks after exposure, but many people remain asymptomatic for longer. Because of this variable timing and frequent absence of symptoms, regular STI testing is recommended after potential exposure or with a new sexual partner.
04 How do you get M. genitalium?
M. genitalium is mainly transmitted through vaginal or anal sex without a condom with an infected partner. Researchers are still studying whether it can spread through oral sex. The bacterium typically infects the urethra, cervix, or rectum. M. genitalium is not spread through casual contact such as hugging, sharing utensils, or using the same toilet.
05 Is M. genitalium curable?
Yes. M. genitalium is curable with appropriate antibiotic treatment prescribed by a doctor, though increasing antibiotic resistance can make treatment more challenging. Untreated M. genitalium may persist and continue to cause symptoms or transmit to partners. Sexual partners should also be tested and treated. Follow-up testing is often recommended to confirm the infection has cleared.
06 How is M. genitalium treated?
M. genitalium is treated with prescription antibiotics. Your doctor will choose the appropriate antibiotic and dosing based on susceptibility (where testing is available), your situation, allergies, and current clinical guidance. Because of resistance concerns, some cases require an extended or alternative course of antibiotics. Complete the prescribed course, avoid sexual activity until completed as advised, and ensure recent partners are also tested and treated.
07 Why is antibiotic resistance a concern with M. genitalium?
M. genitalium has developed significant resistance to some commonly used antibiotics, particularly macrolides (like azithromycin). This makes M. genitalium one of the more challenging STIs to treat. Where available, antibiotic resistance testing helps guide effective treatment selection. Completing the full prescribed treatment course and ensuring partners are also tested and treated are important to prevent further resistance from developing.
08 What are the complications of untreated M. genitalium?
Untreated M. genitalium may be associated with complications, especially in women, including cervicitis, pelvic inflammatory disease, and reproductive health concerns. In men, it may cause urethritis and, less commonly, epididymitis. The exact risk varies, and research is still developing. Testing and appropriate treatment help reduce ongoing symptoms and transmission risk.
09 How can I prevent M. genitalium?
M. genitalium risk can be reduced by using condoms consistently during vaginal, anal, or oral sex, having regular STI screenings (especially with new or multiple partners), maintaining a mutually monogamous relationship with a tested uninfected partner, and ensuring sex toys are cleaned or covered with a fresh condom between partners. Open conversations with partners about STI status also support prevention.
10 Where can I get tested for M. genitalium in Singapore?
You can get tested at Mediway through our STD testing service. Testing may include a urine NAAT test and/or swab, depending on symptoms and exposure. M. genitalium testing is sometimes added to a comprehensive STI panel. The doctor will recommend appropriate tests and discuss treatment if needed. Learn more on our STD testing in Singapore page, or speak to our team for a confidential consultation.
Related conditions and next steps
References: CDC: Mycoplasma genitalium guidelines · WHO: STIs fact sheet · HealthHub Singapore
This page is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare professional for diagnosis and treatment of suspected Mycoplasma genitalium infection.