Mycoplasma genitalium (MG) is a sexually transmitted infection (STI) caused by a very small bacterium that lacks a cell wall. This microorganism is responsible for a growing number of genital tract infections, often mimicking common STIs like Chlamydia. MG is frequently asymptomatic, meaning a person can carry and transmit the infection without knowing they are infected. The timeline for when the bacteria becomes detectable or when symptoms might appear is highly variable.
Incubation Period and Symptom Onset
The time it takes for the MG organism to multiply sufficiently to cause noticeable physical changes, known as the incubation period, is generally longer compared to other bacterial STIs. While highly individual, the onset of symptoms typically ranges from one to three weeks following exposure to the bacteria. Some evidence suggests that the incubation period can extend up to four to eight weeks, particularly due to the organism’s slow replication rate. This extended period means that even if a person develops symptoms, they may not link the discomfort back to a specific sexual encounter.
Most people who contract MG remain asymptomatic; studies indicate this occurs in 70% to 80% of infected men and 50% to 70% of infected women. For these individuals, the infection may persist for months or years without causing apparent health issues, although it can still be transmitted to partners. Symptom onset, when it occurs, is a separate event from the initial infection and depends on the body’s reaction to the increasing bacterial load.
Reliable Detection Testing Timeline
Detecting Mycoplasma genitalium relies on specialized laboratory methods because the bacterium cannot be easily grown using standard culture techniques. The current standard for diagnosis is the Nucleic Acid Amplification Test (NAAT), which detects the organism’s genetic material, DNA, in a sample. For a NAAT test to return an accurate positive result, a minimum bacterial load must be present in the sample, establishing a necessary window period after exposure.
Testing too soon after a potential exposure may yield a false negative result. Although some tests may detect the bacteria as early as five days post-exposure, a more reliable testing window is generally considered to be one to three weeks after the last possible exposure. Waiting for this duration helps ensure that the concentration of the bacteria is high enough for reliable identification. Samples for NAAT testing are typically collected using a urine sample from men or a swab from the vagina or cervix in women.
Manifestation and Presentation
When the infection does cause a symptomatic illness, the presentation differs based on the sex of the individual and the site of the infection. In men, MG is a common cause of non-gonococcal urethritis (NGU), which is an inflammation of the urethra. This inflammation typically presents as a watery or sometimes cloudy discharge from the tip of the penis. Accompanying this discharge, men may experience a burning or painful sensation during urination, a condition known as dysuria.
The infection can also spread beyond the urethra, causing discomfort or pain in the testicles, which is a symptom of epididymitis. For women, a symptomatic infection usually involves the cervix, leading to cervicitis. This often manifests as an unusual or increased vaginal discharge and can be accompanied by bleeding after sexual intercourse or spotting between menstrual periods. Women may also experience pain during sexual intercourse (dyspareunia) and general pain in the lower abdomen or pelvis.
Health Consequences of Delayed Diagnosis
Allowing the MG infection to persist without detection and treatment significantly increases the risk of developing serious long-term complications. In women, an untreated MG infection can ascend from the cervix into the upper reproductive tract, potentially causing Pelvic Inflammatory Disease (PID). PID is a severe infection of the uterus, fallopian tubes, and ovaries that can lead to the formation of scar tissue.
This scarring can block the fallopian tubes, increasing the risk of infertility and a potentially dangerous ectopic pregnancy, where a fertilized egg implants outside the uterus. For men, the upward spread of the infection can result in epididymitis, which is the inflammation of the coiled tube at the back of the testicle that stores and carries sperm. Untreated epididymitis can result in chronic testicular pain and, in some instances, may contribute to male factor infertility. Prompt diagnosis and effective treatment are necessary to prevent these adverse health outcomes.