Ureaplasma and Mycoplasma are types of bacteria often discussed together due to their similar biological features and association with infections in the human genitourinary tract. They are classified under the class Mollicutes and are among the smallest known self-replicating organisms. They are unique because they lack a rigid cell wall, which significantly influences their biology and the methods required to treat them. While they frequently colonize the body without causing harm, they can become opportunistic pathogens.
Defining Ureaplasma and Mycoplasma
The absence of a cell wall is the defining feature of these organisms. This structural difference makes them naturally resistant to common antibiotics, such as penicillins and cephalosporins, which work by targeting the cell wall construction process. Their extremely small size and limited genetic material mean they are highly dependent on a host environment for survival, often existing as parasites on mucosal surfaces.
Four species are most commonly associated with human disease: Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma urealyticum, and Ureaplasma parvum. M. genitalium is generally considered the most significant pathogen, with a clear association with sexually transmitted infections (STIs). Ureaplasma species require and break down urea for energy, a process that can contribute to certain complications in the urinary system.
Transmission Routes and Asymptomatic Carriage
The primary method of acquiring Mycoplasma and Ureaplasma species is through sexual contact, where the organisms are transferred via genital-to-genital or oral-to-genital contact. This sexual route is especially true for M. genitalium, which is recognized as a distinct sexually transmitted pathogen. Risk factors for acquisition include younger age and an increased number of sexual partners.
A secondary route of acquisition is vertical transmission, occurring from a colonized mother to her newborn. This transfer can happen either in utero or during the passage through the birth canal. Vertical transmission is a particular concern with Ureaplasma species, which can colonize the respiratory and genital tracts of the neonate.
These bacteria frequently colonize individuals without causing discernible symptoms, a state known as asymptomatic carriage. Ureaplasma species and M. hominis may be isolated from the lower genital tract in a large percentage of sexually active females. This high prevalence of silent colonization complicates the interpretation of a positive test result, as the organism may be a harmless commensal rather than the actual cause of a patient’s symptoms.
Associated Clinical Conditions and Complications
When these organisms transition from harmless colonizers to active pathogens, they are linked to a spectrum of conditions, primarily affecting the genitourinary system.
Symptoms in Men
In men, infection is a recognized cause of Non-Gonococcal Urethritis (NGU), an inflammation of the urethra that is not caused by gonorrhea. Symptoms of NGU include dysuria (a burning sensation during urination) and a discharge from the penis. Untreated urethritis may progress to more serious complications, such as epididymitis, which is an inflammation of the tube located at the back of the testicle that stores and carries sperm.
Symptoms in Women
In women, M. genitalium is associated with cervicitis (inflammation of the cervix) and Pelvic Inflammatory Disease (PID). PID is a serious condition where bacteria ascend into the upper reproductive tract, potentially causing inflammation of the uterus, fallopian tubes, or ovaries. M. hominis and Ureaplasma species have also been implicated in bacterial vaginosis (BV) and postpartum or post-abortion fever.
Pregnancy and Neonatal Complications
A major area of concern is the impact of these infections during pregnancy and on newborns. Ureaplasma species, in particular, have been strongly associated with adverse outcomes, including an increased risk of preterm birth and premature rupture of membranes (PPROM). The presence of these bacteria can lead to inflammation of the fetal membranes and placenta, known as chorioamnionitis, which is a significant factor in premature delivery. In neonates, especially those born prematurely, Ureaplasma and M. hominis infections can cause serious complications such as pneumonia, meningitis, and chronic lung disease.
Testing Methods and Targeted Treatment
Diagnosing these infections presents a challenge because the organisms are difficult to grow in a laboratory setting, especially the slow-growing M. genitalium. The current standard approach for detection involves using Nucleic Acid Amplification Tests (NAATs), such as Polymerase Chain Reaction (PCR). NAATs identify the specific genetic material of the bacteria, offering a highly sensitive and reliable method for diagnosis that is much faster than traditional culture methods.
Since Ureaplasma and Mycoplasma lack a cell wall, antibiotics that target this structure are ineffective. Effective treatment must rely on antibiotic classes that interfere with protein synthesis, such as macrolides like azithromycin or tetracyclines like doxycycline. The choice of treatment often depends on the specific species identified and the patient’s clinical situation.
A significant challenge in management is the rapidly increasing rate of antibiotic resistance, particularly for M. genitalium against macrolides. Because of this resistance, a single dose of azithromycin is no longer recommended for M. genitalium infection, and resistance-guided therapy is preferred when available. This specialized approach uses a test to determine the antibiotic susceptibility of the specific strain before prescribing medication.