Mycoplasma genitalium (MG) – A Sexually Transmitted Infection

Mycoplasma genitalium (MG) is a type of bacteria that spreads through sexual contact and infects mucous membranes such as the urethra, cervix, and rectum. Although many people remain asymptomatic, MG can cause chronic inflammation and complications if left untreated.

In recent years, the increasing antibiotic resistance of MG has become a significant concern.

Main Symptoms

While many infected individuals do not experience symptoms, the following may occur depending on the site of infection:

In Men:

Urethritis (pain or discomfort during urination)
Penile discharge
Discomfort or pain around the testicles

In Women:

Cervicitis (inflammation of the cervix)
Abnormal vaginal discharge
Lower abdominal pain, pain during intercourse
Postcoital bleeding
If left untreated, it may progress to Pelvic Inflammatory Disease (PID)

In All Genders: Proctitis (Rectal Infection)

Particularly common in:

Men who have sex with men (MSM)
Individuals who engage in receptive anal sex
People living with HIV

Symptoms of Rectal Infection:

Anal pain or discomfort
Mucous or purulent rectal discharge
Tenesmus (a feeling of incomplete bowel evacuation)
Rectal bleeding

Note: Rectal infections are often asymptomatic and may be missed without proper testing. Therefore, routine rectal screening is recommended for individuals with a history of anal sex, especially MSM.

Testing

The primary method of diagnosis is nucleic acid amplification testing (NAAT).

Sample Collection Sites:

Men: First-pass urine sample
Women: Vaginal or cervical swab
MSM / Receptive anal sex: Rectal swab

Treatment

Treatment is best guided by antimicrobial resistance results, in a two-step approach:

Step 1:
Doxycycline 100 mg twice daily for 7 days
Step 2 (depending on resistance):
1. Macrolide-sensitive strains:
  Azithromycin: 1g on day 1, then 500 mg daily for days 2–4
1. Macrolide-resistant strains:
  Moxifloxacin 400 mg once daily for 7 days

Empirical treatment or treatment without resistance testing is not recommended.

Partner Management & Reinfection Prevention

Sexual partners from the past 6 months should:
- Be tested for MG
- Refrain from sexual contact until treatment is completed
Test of Cure is recommended 3–4 weeks after treatment, especially for rectal infections or resistant cases.

Prevention

Use of condoms or barrier protection during sexual activity is the most effective prevention.
Regular screening is recommended for:
- MSM (Men who have sex with men)
- Those who have had contact with STI-positive partners
- Sex workers
- People living with HIV

Public Health Considerations

The rise in antibiotic-resistant MG makes treatment more challenging.
In women, untreated MG can lead to infertility and PID.
Rectal infections are often underdiagnosed — proactive screening is advised for MSM and those with a history of anal sex.

Melbourne Sexual Health Centre (MSHC) Guidelines

Routine screening is not recommended for asymptomatic individuals.
Testing and treatment are advised only for those with symptoms or identified risk factors.
Testing should include screening for other STIs such as chlamydia, gonorrhoea, HIV, and syphilis.

For those seeking evaluation or treatment for Mycoplasma genitalium, please feel free to contact Skyarch Medical Clinic Brisbane.

Dr. Tatsuro Nagashima

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