How Mycoplasma Genitalium Is Diagnosed

Mycoplasma bacteria

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Mycoplasma genitalium (MG) is a lesser-known but otherwise common sexually transmitted disease (STD). Despite this, few doctors ever screen for the disease and instead assume that MG is involved in certain circumstances.

For example, if you have symptoms of urethritis or cervicitis but test negative for gonorrhea and chlamydia, your doctor may presumptively treat you for MG. This is because MG is the most common cause of urethritis and cervicitis next to the other two, more familiar diseases.

In fact, around one of every 100 adults is thought to have MG, while more than three of every 100 gay or bisexual men are believed to be infected, according to a 2018 study published in Sexually Transmitted Infections.

There are times, however, when it is necessary to pinpoint mycoplasma as the cause, and it's not always a straightforward task.

Self Checks

Because of its frequency in adult populations, MG is almost presumed to be the cause of urethritis (inflammation of the urethra) or cervicitis (inflammation of the cervix) when gonorrhea and chlamydia have been excluded. This is due in part to the fact that MG can be spread so easily, often through sexual touching or rubbing rather than through intercourse.

Moreover, MG is not always symptomatic, so you may not even know if you have it or can potentially spread the infection to others.

If symptoms do develop, they can vary significantly by sex.

In women, the symptoms may include:

  • Vaginal sex
  • Pain during sex
  • Bleeding after sex
  • Spotting between periods
  • Pain in the pelvic area just below the navel

In men, the symptoms include:

  • Watery discharge from the penis
  • Burning, stinging, or pain when urinating

While symptoms alone cannot diagnose MG, ones like these are a strong indication that some sort of infection has occurred. It is vital, therefore, to seek a proper diagnosis, especially in women.

If left untreated, MG can lead to pelvic inflammatory disease (PID), a condition that can interfere with your ability to get pregnant. It is unknown whether untreated MG may also interfere with male fertility.

Labs and Tests

There are challenges to diagnosing MG given the lack of an FDA-approved test. Still, it may be important to isolate MG as the cause, particularly if urethritis or cervicitis is recurrent and fails to respond to antibiotic therapy.

This is of concern given that that antibiotic-resistance MG is believed to be building in North America, according to a 2017 study from the Public Health Agency of Canada.

Isolating MG as the cause can aid in the selection of the most appropriate antibiotic and exclude those more closely linked to resistance (such as macrolides like azithromycin and fluoroquinolones like ciprofloxacin).

If MG testing is indicated, an assay known as the nucleic acid amplification test (NAAT) is the preferred method of diagnosis. It can be used to test urine, endometrial biopsies, and urethral, vaginal, and cervical swab.

The NAAT tests for the genetic material of MG rather than trying to grow the bacteria in a culture (something that is next to impossible to do). It is not only accurate but fast, usually returning a result in 24 to 48 hours. (The NAAT is also considered the gold standard method of testing for chlamydia.)

The NAAT employs a technology called polymerase chain reaction (PCR) in which the genetic material of an organism is amplified—essentially photocopied again and again—to facilitate accurate detection.

The NAAT is not without its challenges. Unless performed correctly, the test may return a false-negative result. To overcome this, the provider should ideally take a urine sample as well as a swab of the urethra, vagina, or cervix. This essentially doubles the risk of a correct diagnosis and helps overcome errors in sample collection.

Differential Diagnoses

If an inconclusive or borderline result is returned, the doctor may perform a repeat NAAT and/or broaden the scope of the investigation. Presuming that chlamydia and gonorrhea have already been ruled out, the investigation (known as differential diagnosis) may include:

  • Bacterial vaginosis
  • E. coli cystitis
  • Herpes simplex virus (HSV) urethritis
  • Prostatitis
  • Salpingitis (inflammation of the fallopian tubes)
  • Syphilis
  • Trichomonas vaginalis
  • Ureaplasma urealyticum (a genital tract bacterial infection)
  • Urethral abscess

Some of these, like syphilis and bacterial vaginosis, are more likely to have been investigated prior to MG. The others may only be performed once the more likely causes of urethritis and cervicitis have been ruled out.

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