Mycoplasma genitalium (M. gen) is a bacterium recognized as an increasingly prevalent sexually transmitted infection (STI) that affects the urinary and genital tracts. This microorganism is particularly challenging to detect because it often causes no noticeable symptoms in infected individuals. Accurate and timely diagnosis is important due to its potential for serious health complications if left untreated. The methods for testing have evolved significantly, moving away from unreliable traditional techniques to highly sensitive molecular diagnostics.
Why Testing for M. gen is Essential
Testing for M. gen is essential because the infection can silently progress to cause serious reproductive health issues in both men and women.
In men, the bacterium is a common cause of non-gonococcal urethritis (NGU), which can lead to symptoms like discharge and painful urination. Untreated infection may also progress to epididymitis, a painful inflammation of the tube that stores and carries sperm.
In women, the consequences are potentially more severe, often mimicking other common STIs. The infection is associated with cervicitis and can ascend into the upper reproductive tract to cause Pelvic Inflammatory Disease (PID). PID can lead to long-term reproductive problems, including chronic pelvic pain, tubal factor infertility, and an increased risk of ectopic pregnancy. Since many cases remain asymptomatic, testing is the only way to prevent these complications and interrupt transmission.
Primary Diagnostic Methods
The inability to grow M. gen reliably in a laboratory setting is a significant hurdle, as the organism is fastidious and may take months to culture. Consequently, the current standard for detection relies entirely on modern molecular techniques known as Nucleic Acid Amplification Tests (NAATs). These tests work by detecting the genetic material (DNA or ribosomal RNA) of the bacterium directly from a patient sample.
Polymerase Chain Reaction (PCR) is a widely used NAAT that amplifies specific DNA sequences, allowing for the detection of even very low levels of the bacteria. Some advanced NAATs, like those using Transcription-Mediated Amplification (TMA), target the organism’s rRNA, which can offer higher sensitivity.
The high sensitivity and specificity of these molecular tests are crucial because the bacterial load of M. gen in patient samples is often low compared to other STIs. These diagnostic advancements permit clinicians to distinguish M. gen from other infections that present with similar symptoms, ensuring the correct treatment is prescribed.
Sample Collection and Patient Preparation
The accuracy of M. gen testing depends on collecting an appropriate sample that contains the highest concentration of the bacteria.
Sample Collection for Men
For men, the preferred sample is a first-catch urine specimen, which is the initial 20 to 30 milliliters of the urine stream. This first portion of urine is important because it washes out the cells containing the bacteria that are shed from the urethra. To maximize the concentration of the bacteria, patients must refrain from urinating for at least one to two hours before collection.
Sample Collection for Women
For women, a vaginal swab is often the preferred specimen type, as studies suggest it offers the greatest sensitivity for detecting the infection. Vaginal swabs can be collected by the patient in a clinical setting or at home, which can improve patient comfort and screening compliance.
Alternative samples include a cervical swab collected during a clinical examination or a first-catch urine sample, though urine is generally less sensitive. Patients providing a swab should avoid douching or using vaginal creams for 24 hours prior to collection, as these can interfere with the test results. Proper sample handling, including transferring the collected material into the specialized transport media, is necessary to maintain the sample’s integrity before laboratory analysis.
Understanding and Acting on Test Results
Test results for M. gen are typically reported as either “Detected” (positive) or “Not Detected” (negative) and are usually available within a few days. A positive result confirms the presence of the bacterium and necessitates immediate treatment, usually with a course of two different antibiotics given sequentially. Coinfections with other STIs, such as Chlamydia or Gonorrhea, are common, and testing for these is often performed concurrently.
A significant concern with this infection is the high rate of macrolide resistance, particularly to azithromycin. Resistance testing is increasingly recommended, where available, to guide the selection of the most effective antibiotic, such as moxifloxacin for resistant strains. The treating clinician will often recommend testing and treating all recent sexual partners to prevent reinfection and limit further spread.
Following the completion of treatment, a “Test of Cure” (TOC) is often performed to confirm that the infection has been successfully eradicated. The TOC is typically a repeat NAAT performed 14 to 21 days after the patient has finished all antibiotics. This follow-up testing is important in cases where resistance is suspected or when the initial treatment regimen failed.