Mycoplasma
Mycoplasma is a genus of bacteria that belongs to the class Mollicutes and is known for its minimalistic structure, lacking a cell wall, which makes it resistant to certain antibiotics. This bacterial group includes several species that are recognized as human pathogens, particularly Mycoplasma pneumoniae, Mycoplasma hominis, and Mycoplasma genitalium. Mycoplasma can be found in both humans and various animals and is capable of surviving in diverse environments, with some species able to invade host cells and cause infections.
Mycoplasma pneumoniae is most commonly associated with respiratory infections, often referred to as atypical pneumonia. It is transmitted through respiratory droplets, making crowded settings like schools and shelters places of increased risk. Other Mycoplasma species are linked to urogenital diseases and can cause various conditions, including nonchlamydial urethritis, chorioamnionitis, and neonatal meningitis. Treatment for Mycoplasma infections varies depending on the species and the severity of the infection, with certain antibiotics being preferred despite emerging resistance issues.
The growing prevalence of Mycoplasma pneumoniae infections, particularly among younger children, has been noted recently, marking a shift from lower infection rates during the COVID-19 pandemic. Understanding Mycoplasma's transmission routes, pathogenicity, and treatment options is crucial for addressing the public health challenges it poses.
Mycoplasma
- TRANSMISSION ROUTE: Blood, inhalation
Definition
Mycoplasma is a bacterial genus belonging to the class Mollicutes. Several Mycoplasma species have been established as human pathogens, including pneumoniae, hominis, and genitalium.
Natural Habitat and Features
Mycoplasma has been isolated from humans and animals, including cows, dogs, cats, pigs, horses, poultry, sheep, goats, and small rodents. Mycoplasma is one of the smallest bacteria that can live independently. It has a small genome size that is in the lower limit of complexity necessary for self-replicating organisms. Mycoplasma can survive in the presence or absence of oxygen.
Mycoplasma lacks a cell wall, so it does not react in a Gram’s stain and is not susceptible to antibiotics that target cell walls. It has a specialized organelle, or tip, that provides motility and mediates bacterial interactions with its host cells. Adherence proteins allow Mycoplasma attachment to cells lining the respiratory and genitourinary tracts, acting like a parasite on the surface of its host cells and using their precursors for production of its genetic material. Some species (pneumoniae, genitalium, fermentans, penetrans, and gallisepticum, a poultry pathogen) can invade host cells and live intracellularly.
Mycoplasma produces hydrogen peroxide and superoxide, substances that cause injuries to the mucosal surface; the activation of inflammatory mediators is associated with its infectious process. Mycoplasma is challenging to grow in culture; thus, bacterial identification mainly depends on molecular-biochemical techniques.
Pathogenicity and Clinical Significance
Although there are seven Mycoplasma species detected in the human genitourinary tract, only three species (genitalium, hominis, and Ureaplasma species) are associated with urogenital disease. Nonchlamydial nongonococcal urethritis in men may result from genitalium and Ureaplasma species. Genitalium has also been isolated from the urogenital tract of women with cervicitis and pelvic inflammatory disease. Genitalium and Ureaplasma species have also been implicated in extragenital infections.
Hominis and Ureaplasma species have been implicated in chorioamnionitis, endometritis, pyelonephritis, postpartum or postabortum fevers, neonatal meningitis, pneumonia, bacteremia, and arthritis (specifically, hominis in postpartum women and Ureaplasma species in sexually acquired reactive arthritis).
Hominis has been related to extragenital infections, including sepsis, hematoma infection, vascular and catheter-related infections, sternal wound infections following thoracic surgery, prosthetic valve endocarditis, brain abscesses, and pneumonia. These infections occurred mainly through the spread of bacteria in the bloodstream and mostly in immunocompromised persons who had injuries of anatomical barriers and polytrauma.
Pneumoniae causes lung infections, often called atypical pneumonia or walking pneumonia. It is transmitted through respiratory droplets between persons. At the highest risk for infection are those persons who are in close contact with others, including those who live, work, or perform activities in crowded places such as schools, homeless shelters, hospitals, prisons, and dormitories. Other risk factors for Mycoplasma respiratory infection include smoking and lower levels of preexisting immunoglobulin G levels. Mycoplasma pneumonia has pulmonary manifestations (such as nonproductive cough) and extrapulmonary manifestations (such as cardiologic, neurologic, and dermatologic symptoms). There is no age or gender predilection for the disease. Although people of all ages are at risk, infection less frequently occurs in children younger than five years of age.
Drug Susceptibility
Hominis is treated with tetracycline, the drug of choice, usually for seven days, but the duration of treatment is based on observations of symptom resolution and clinical judgment. Resistant strains have been reported, and alternate choices of antibiotics include clindamycin and fluoroquinolones (such as gatifloxacin and moxifloxacin).
Ureaplasma infections are treated with tetracycline or erythromycin, although azithromycin has become a preferred treatment. A seven-day course of doxycycline can also be used to treat urethritis caused by Ureaplasma species. Alternative antimicrobials for Ureaplasma include fluoroquinolones (such as levofloxacin and ofloxacin) and chloramphenicol. Clinical observations are important when considering treatment duration.
Neonatal meningitis caused by hominis and Ureaplasma species is often treated with tetracyclines despite contraindications for use in children. Alternative medications for use in children include chloramphenicol for both bacteria, clindamycin for hominis, and erythromycin for Ureaplasma species. Lower respiratory infections in newborns can be treated with azithromycin or erythromycin. The suggested duration of treatment for Mycoplasma infections in newborns is ten to fourteen days.
Genitalium and pneumonia are treated with macrolides (such as azithromycin, clarithromycin, and erythromycin), fluoroquinolones (such as levofloxacin and moxifloxacin), and tetracyclines (such as doxycycline). The duration of treatment ranges from five to fourteen days, depending on what antibiotic is used. Due to emerging antibiotic resistance, a two-step approach is often used with initial treatment with doxycycline, followed by either azithromycin or moxifloxacin. In 2024, the Centers for Disease Control and Prevention noted that M. pneumonia infections were increasing drastically, especially among younger children, both worldwide and in the United States. However, previous infection levels had fallen during the COVID-19 pandemic.
Bibliography
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