Mycoplasma genitalium (MG) is a sexually transmitted bacterium that has become an increasingly recognized public health concern. This infection frequently goes undiagnosed because its signs are easily mistaken for those of other, more common sexually transmitted infections (STIs), such as Chlamydia or Gonorrhea. MG presents a challenge due to its unique biological nature and a rapidly evolving pattern of antimicrobial resistance. This overview provides information regarding the organism, the physical changes it causes, how it is detected, and the process required for successful treatment.
Defining Mycoplasma Genitalium
Mycoplasma genitalium is a bacterium distinguished by its small size and unique structural feature: it completely lacks a cell wall. This absence means that many common classes of antibiotics, such as penicillins and cephalosporins, which work by attacking the bacterial cell wall, are entirely ineffective against MG. The organism possesses one of the smallest genomes among self-replicating bacteria, making it a slow-growing microbe.
Transmission of MG occurs primarily through unprotected sexual contact, including vaginal and anal intercourse. The organism has specialized mechanisms, like adhesins, that allow it to strongly attach to the epithelial cells lining the urogenital tract. This adherence enables it to colonize the urethra in both sexes and the cervix in women. The infection is highly transmissible.
Manifestations of Infection
A significant number of individuals infected with Mycoplasma genitalium will experience no outward physical changes, meaning the infection is entirely asymptomatic. This silent nature allows the bacterium to be passed on unknowingly and potentially cause long-term complications if it remains untreated. When manifestations do occur, they typically begin within one to three weeks following exposure, but the symptoms often mimic those of other STIs.
Symptoms in Males
In males, the infection most commonly leads to non-gonococcal urethritis (NGU), which is an inflammation of the urethra. This condition presents with a watery or thin discharge from the penis that may be clear or slightly cloudy. Men may also experience dysuria, a burning or painful sensation during urination. In some cases, the infection can ascend, causing epididymitis, an inflammation of the coiled tube at the back of the testicle, resulting in testicular pain or swelling.
Symptoms in Females
For females, the infection can target the cervix, causing cervicitis, or the urethra, causing dysuria. Cervicitis may result in an abnormal vaginal discharge, or bleeding after sexual intercourse. The infection can travel higher into the reproductive system, leading to pelvic inflammatory disease (PID). PID affects the uterus, fallopian tubes, and ovaries. PID can manifest as lower abdominal pain, discomfort during sex, and abnormal bleeding between menstrual periods. Untreated PID can cause scarring in the fallopian tubes, which increases the risk of chronic pelvic pain and infertility.
Identifying the Infection
Accurate identification of Mycoplasma genitalium requires specialized laboratory methods due to the organism’s unique characteristics. The bacterium’s extremely slow growth rate makes traditional bacterial culture techniques impractical for clinical diagnosis. A culture for MG can take up to six months to yield results, which is far too long for effective patient management.
The standard and most reliable method for detection is the Nucleic Acid Amplification Test (NAAT), often using Polymerase Chain Reaction (PCR) technology. These tests amplify and detect the specific genetic material of the bacterium from a patient sample. Samples are typically collected via urine for men, and a vaginal or endocervical swab for women. Rectal or pharyngeal swabs may be used depending on exposure.
Testing is generally recommended for individuals showing physical signs of urethritis or cervicitis, or when a partner has been diagnosed with the infection. Routine screening for MG in the general population is not universally recommended due to the high number of asymptomatic cases and the cost of specialized testing. Testing is often performed when a patient has symptoms of urethritis or cervicitis that have not cleared up after treatment for other common STIs like Chlamydia.
Treatment Protocols and Resistance
Treating Mycoplasma genitalium has become increasingly complex due to the rapid development of antimicrobial resistance. The organism’s unique lack of a cell wall means that treatment must rely on specific classes of antibiotics, primarily macrolides like azithromycin and fluoroquinolones like moxifloxacin. Widespread resistance to azithromycin is common, with rates reaching 30% to over 50% in some regions.
To address this challenge, medical guidelines now frequently recommend a two-stage sequential therapy approach, especially when macrolide resistance is suspected or confirmed. This protocol often begins with a course of doxycycline, used to reduce the overall bacterial load. Doxycycline is then followed by a higher-dose macrolide or a fluoroquinolone, such as moxifloxacin, to achieve complete eradication.
Following the completion of the antibiotic regimen, a Test of Cure (TOC) using a NAAT is advised for all patients. This follow-up test confirms that the bacterium has been completely cleared and that a drug-resistant strain has not persisted, which is crucial for preventing further transmission.