Notes
Mycoplasmas & Ureaplasmas
Sections
Mycoplasma and Ureaplasma.
The smallest free-living bacteria.
No cell wall.
– Consequently, they stain poorly and are resistant to penicillin and other antibacterial drugs that target the cell wall.
Their cell membranes contain sterols, which is unique.
They are facultative anaerobes – except for Mycoplasma pneumoniae, which is a strict aerobe.
When cultured, they grow slowly, and have a fried-egg appearance.
Mycoplasma pneumoniae
Aka, "Eaton agent."
Causes a range respiratory infections, from mild cases of tracheobronchitis to severe cases of atypical pneumonia.
Infection spreads slowly among individuals living in close contact, such as families.
Some people will be asymptomatic.
Long incubation period, and infection can persist for months.
Post-infection, acquired immunity tends to be short-lived and incomplete.
Diagnostic tests include PCR amplification and ELISA.
Respiratory Infections
Treatment: erythromycin, doxycycline, or fluoroquinolones; be aware that macrolide-resistant strains are a growing concern.
Transmission of the bacteria occurs via respiratory droplets.
Primary site of infection is the respiratory tract.
Mycoplasma pneumonia has an attachment organelle that facilitates motility and adherence to these cells; P1 adhesins are key in this process.
After attachment, the bacteria destroy the ciliated cells, which inhibits microbial clearance from the respiratory tract.
– Cellular destruction is achieved via production of hydrogen peroxide and Community Acquired Respiratory Distress Syndrome exotoxin (CARDS).
The bacteria acts as superantigens: they recruit and activate inflammatory cells, leading to the release of cytokines; inflammatory cells and their products are responsible for many of the clinical manifestations of infection.
Extrapulmonary infections
Treated with corticosteroids or immunoglobulins; patients with thrombosis should be given anticoagulants.
These infections are the result of inflammatory cytokines, autoimmunity, and the formation of immune complexes.
Individuals may experience neurological or cardiac diseases, thrombosis, hemolytic anemia, arthritis, or cutaneous/mucosal lesions such as Stevens-Johnson Syndrome.
– Be aware that these issues may arise in the presence or absence of atypical pneumonia.
Opportunistic Pathogens
Primarily affect the urogenital tract.
Bacteria are transmitted via sexual activity (contact with infected mucosal surfaces).
Mycoplasma genitalium
Infection is often asymptomatic.
It is a common cause of non-gonococcal urethritis in men.
Associated with cervicitis, pelvic inflammatory disease, and adverse pregnancy outcomes in women.
Treat with: azithromycin or moxifloxacin.
Mycoplasma hominis and Ureaplasma urealyticum
Common colonizers of the female reproductive tract.
Mycoplasma hominis is associated with postpartum fever and pyelonephritis.
Treat with clindamycin.
Ureaplasma urealyticum is associated with urethritis, pyelonephritis, and adverse pregnancy outcomes.
Treated with Erythromycin.
Ureaplasma urealyticum produces urease, which differentiates it from the Mycoplasmas.
Vertical Transmission & Neonatal Infection
Both Mycoplasma hominis and Ureaplasma urealyticum can be vertically transmitted from mother to fetus;
In the neonate, these bacteria are associated with pulmonary disease, bacteremia, and meningitis; treatment of infected mothers may prevent transmission and neonatal disease.
Full-Length Text
Here we will learn about pathogenic strains of Mycoplasma and Ureaplasma.
To begin, write that they are the smallest free-living bacteria.
They have no cell wall; consequently, they stain poorly and are resistant to penicillin and other antibacterial drugs that target the cell wall.
Their cell membranes contain sterols, which is unique.
They are facultative anaerobes – except for Mycoplasma pneumoniae, which is a strict anaerobe.
When cultured, they grow slowly, and have a fried-egg appearance.
Let's now learn about a strictly pathogenic species, Mycoplasma pneumonia; be aware that it is sometimes called "Eaton agent."
Indicate that it causes a range respiratory infections, from mild cases of tracheobronchitis to severe cases of atypical pneumonia.
Infection spreads slowly among individuals living in close contact, such as families.
And, some people will be asymptomatic.
Mycoplasma pneumoniae has a long incubation period, and the infection can persist for months.
Post-infection, acquired immunity tends to be short-lived and incomplete.
Diagnostic tests include PCR amplification and ELISA.
Indicate respiratory infections caused by Mycoplasma pneumoniae can be treated with erythromycin, doxycycline, or fluoroquinolones; be aware that macrolide-resistant strains are a growing concern.
Then, show that transmission of the bacteria occurs via respiratory droplets, and, that the respiratory tract is the primary site of infection.
Draw some ciliated cells of the respiratory tract, and show that:
Mycoplasma pneumonia has an attachment organelle that facilitates motility and adherence to these cells; P1 adhesins are key in this process.
Indicate that, after attachment, the bacteria destroy the ciliated cells, which inhibits microbial clearance from the respiratory tract.
Write that cellular destruction is achieved via production of hydrogen peroxide and Community Acquired Respiratory Distress Syndrome exotoxin (CARDS).
And, that the bacteria acts as superantigens: they recruit and activate inflammatory cells, leading to the release of cytokines; inflammatory cells and their products are responsible for many of the clinical manifestations of infection.
This is particularly relevant to understanding the extrapulmonary infections caused by Mycoplasma pneumoniae.
Show that, as the result of inflammatory cytokines, autoimmunity, and the formation of immune complexes, individuals may experience neurological or cardiac diseases, thrombosis, hemolytic anemia, arthritis, or cutaneous/mucosal lesions such as Stevens-Johnson Syndrome. Be aware that these issues may arise in the presence or absence of atypical pneumonia.
Write that extrapulmonary infections can be treated with corticosteroids or immunoglobulins; patients with thrombosis should be given anticoagulants.
Next, let's consider some opportunistic pathogens of the urogenital tract.
Write that these bacteria are transmitted via sexual activity (contact with infected mucosal surfaces).
Write that Mycoplasma genitalium infection is often asymptomatic;
However, it is also a common cause of non-gonococcal urethritis in men, and is associated with cervicitis, pelvic inflammatory disease, and adverse pregnancy outcomes in women.
These infections are treated with azithromycin or moxifloxacin.
Mycoplasma hominis and Ureaplasma urealyticum are common colonizers of the female reproductive tract.
However, they act as opportunistic pathogens associated with the following infections:
Mycoplasma hominis is associated with postpartum fever and pyelonephritis; Clindamycin is the recommended treatment.
Ureaplasma urealyticum is associated with urethritis, pyelonephritis, and adverse pregnancy outcomes; infection is treated with Erythromycin.
Ureaplasma urealyticum produces urease, which differentiates it from the Mycoplasmas.
Lastly, indicate that both Mycoplasma hominis and Ureaplasma urealyticum can be vertically transmitted from mother to fetus;
In the neonate, these bacteria are associated with pulmonary disease, bacteremia, and meningitis; treatment of infected mothers may prevent transmission and neonatal disease.
References:
Murray, P. R., Rosenthal, K. S., & Pfaller, M. A. Medical microbiology. Philadelphia: Elsevier/Saunders. (2013).
Levinson, W. E. Review of Medical Microbiology and Immunology. 14th Ed. Lange (2016).
Capoccia, R., Greub, G., Baud, D. (2013). Ureaplasma urealyticum, Mycoplasma hominis and adverse pregnancy outcomes. Current Opinion Infectious Disease. 26:231–240.
Bayraktar, M.R., Ozerol, I.H., Gucluer, N., Celik, O. (2010). Prevalence and antibiotic susceptibility of Mycoplasma hominis and Ureaplasma
urealyticum in pregnant women. International Journal of Infectious Diseases. 14: e90—e95.
Narita, M. (2010). Pathogenesis of extrapulmonary manifestations
of Mycoplasma pneumoniae infection with special reference to pneumonia. J Infect Chemother. 16:162–169.
Waites, K.B., Xiao, L., Liu, Y., Balish, M.F., Atkinson, T.P. (2017). Mycoplasma pneumoniae from the Respiratory Tract and Beyond. Clin
Microbiol Rev 30:747– 809.
Lis, R., Rowhani-Rahbar, A., Manhart, L.E. (2015). Mycoplasma genitalium Infection and Female Reproductive Tract Disease: A Meta-analysis. Clinical Infectious Diseases. 61(3):418–26.
Jensen, J.S., Cusini, M., Gomberg, M., Moi, H. (2016). 2016 European guideline on Mycoplasma genitalium infections. Journal of the European Academy of Dermatology and Venereology. DOI: 10.1111/jdv.13849.