Mycoplasma pneumoniae
From Wikipedia, the free encyclopedia
| Mycoplasma pneumoniae | ||||||||||||||
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| Scientific classification | ||||||||||||||
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| Binomial name | ||||||||||||||
| Mycoplasma pneumoniae Somerson et al., 1963 |
| Mycoplasma pneumoniae as the cause of diseases classified to other chapters Classification and external resources |
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| ICD-10 | B96.0 |
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| ICD-9 | 483.0 |
Mycoplasma pneumoniae is a very small bacterium, in the class Mollicutes. This class of organisms lack a peptidoglycan cell wall present on all other firmicute bacteria. Instead, it has a cell membrane which incorporates sterol compounds, similar to eukaryotic cells. It obtains these sterols from the host serum, allowing it to retain a simple structure. Lacking a cell wall, these organisms are resistant to the effects of penicillins and other beta-lactam antibiotics, which act by disrupting the bacterial cell wall.
M. pneumoniae has one of the smallest genomes known, with 816 kilobase pairs (kbs). Its genome and proteome has been fully characterized. It uses some unique genetic code, making its code more similar to mitochondria than to other bacteria. Thus it is said that Mycoplasma pneumoniae has a degenerate genome. It lacks the cellular machinery for making many essential compounds, including new purines and pyrimidines. It also has no tri-carboxylic acid cycle and an incomplete electron transport chain. Because of this, it is an obligate parasite and is never found free-living.
M. pneumoniae is spread through respiratory droplet transmission. Once attached to the mucosa of a host organism, M. pneumonia extracts nutrients, grows and reproduces by binary fission. Attachment sites include the upper and lower respiratory tract, causing pharyngitis, bronchitis and pneumonia. The infection caused by this bacterium is called atypical pneumonia because of its protracted course and lack of sputum production and wealth of extra-pulmonary symptoms. Chronic mycoplasma infections have been implicated in the pathogenesis of rheumatoid arthritis and other rheumatological diseases.
M. pneumoniae infections can be differentiated from other types of pneumonia by the relatively slow progression of symptoms, a positive blood test for cold-hemagglutinins in 50-70% of patients after 10 days of infection (cold-hemagglutinin-test should be used with caution or not at all since 50% of the tests are false-positive), lack of bacteria in a gram-stained sputum sample, and a lack of growth on blood agar. Mycoplasma atypical pneumonia can be complicated by Stevens-Johnson syndrome, hemolytic anemia, encephalitis or Guillain-Barré syndrome.
Second generation macrolide antibiotics, doxycycline and second generation quinolones are effective treatments. Disease from mycoplasma is usually mild to moderate in severity.
M. pneumoniae was historically called "Eaton's agent"[1] because it is grown on Eaton's agar.
