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What is Mycoplasma Genitalium?
Mycoplasma genitalium (M. gen) is a sexually transmitted bacterium increasingly recognised as a significant pathogen. It's one of the smallest known bacteria, lacking a cell wall, which makes it naturally resistant to common antibiotics like penicillin. M. gen causes urethritis in men and cervicitis and PID in women. Antibiotic resistance is rising rapidly, making resistance-guided treatment essential.
Symptoms
- Many infections are asymptomatic (especially women)
- Men: urethral discharge, painful urination, urethral discomfort
- Women: abnormal vaginal discharge, bleeding after sex, intermenstrual bleeding
- Pelvic pain in women
- Rectal discomfort or discharge (rectal infection)
- Symptoms may be milder than gonorrhoea
- Can persist without treatment for months to years
Causes
- Mycoplasma genitalium bacterium
- Unprotected vaginal sex
- Unprotected anal sex
- Possibly oral sex (less common)
- The bacterium infects mucosal cells
- Can establish persistent infection
- Transmission requires direct mucosal contact
Who Is at Risk?
- Sexually active individuals
- People with multiple sexual partners
- People with other STIs
- Young adults
- People with symptoms of urethritis or cervicitis
- Sexual partners of infected individuals
- People with persistent urogenital symptoms despite treatment
Potential Complications
- Pelvic inflammatory disease (PID) in women
- Increased risk of infertility
- Ectopic pregnancy risk
- Chronic pelvic pain
- Epididymitis in men
- Reactive arthritis (rare)
- Increased HIV transmission/acquisition
- Persistent infection with resistant strains
How We Diagnose
M. gen requires specific PCR testing - it's not detected by standard bacterial cultures. We can test urine, vaginal swabs, or rectal swabs. Importantly, resistance testing should be performed on positive samples to guide treatment. If you've had persistent symptoms despite treatment for other infections, M. gen testing is recommended.
Treatment Options
Due to high resistance rates, treatment should be guided by resistance testing. First-line is typically azithromycin if susceptible. Macrolide-resistant strains require moxifloxacin or other alternatives. A test of cure 3-5 weeks after treatment is essential. Partner treatment is important to prevent reinfection. Untreated infection can persist for years.
Prevention
Frequently Asked Questions
Why isn't M. gen included in standard STI tests?
Testing for M. gen requires specific PCR technology and isn't yet part of routine screening in many settings. It's relatively newly recognised as an important pathogen. We recommend M. gen testing if you have symptoms, persistent infections, or multiple partners. As awareness grows, testing is becoming more available.
I've been treated for chlamydia but symptoms persist - could it be M. gen?
Possibly. M. gen causes similar symptoms to chlamydia and isn't detected by chlamydia tests. If you have persistent symptoms after completing chlamydia treatment, M. gen is an important possibility. We can test specifically for M. gen and other causes of persistent urethritis or cervicitis.
Why is antibiotic resistance a concern with M. gen?
M. gen develops resistance very quickly. Around 50% or more of strains in the UK are now resistant to azithromycin (first-line treatment). Using the wrong antibiotic or not completing treatment promotes resistance. This is why we recommend resistance testing before treatment and test of cure afterwards.
Does my partner need treatment for M. gen?
Yes, sexual partners from the past 3 months should be tested and treated if positive. Even if asymptomatic, partners can be infected and reinfect you. Both partners should avoid sex until treatment is complete and test of cure is negative. This prevents ping-pong reinfection.
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Concerned About Mycoplasma Genitalium?
Book a confidential consultation or STI test at our South Kensington clinic. Walk-in appointments available.



