Mycoplasma pneumonia is a very small bacterium in the class Mollicutes. It is a human pathogen that causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia related to cold (...)
Mycoplasma pneumonia is a very small bacterium in the class Mollicutes. It is a human pathogen that causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia related to cold agglutinin disease. M. pneumonia is characterised by the absence of a peptidoglycan cell wall and resulting resistance to many antibacterial agents. The persistence of M. pneumonia infections even after treatment is associated with its ability to mimic host cell surface composition. M.pneumoniae is the etiological agent of more than 20% of cases of atypical pneumonia in adults and school-age children, various infections of the upper and lower respiratory tract, and extrapulmonary lesions. The causative agent is highly contagious and is transmitted from person to person by airborne droplets, especially in close contact in isolated groups (family, school, military force). Outbreaks of pneumonia caused by mycoplasma occurs at any time of year, but most often they are recorded in late summer and autumn. Epidemics of M. pneumonia tend to repeat every 4-8 years, often in closed populations. Mainly affected are patients aged 5 to 18 years; children aged 3-5 years and people over 20 years are infected less frequently.
M. pneumoniae infection may be clinically manifested or asymptomatic. Typical clinical manifestations are fever, dry cough and headache. These clinical manifestations are observed in only 3-10% of those infected. General signs of M.pneumoniae infection are nonspecific and do not allow a differential diagnosis and determination of a causative agent of the disease. For this purpose, methods of laboratory diagnosis are applied, which include direct detection of the pathogen and serological studies.
Reference method of laboratory diagnostics is isolation of M. pneumoniae in cell culture. However, this method is characterized by low sensitivity, laboriousness and time consuming (3-5 days).
The most informative serological methods are complement fixation (CFT), agglutination test (AT) and enzyme-linked immunosorbent assay (ELISA). The latter, in contrast of first two, allows the identification specific antibodies of classes IgG, IgA and IgM.
Specific IgM antibodies reach high levels in 1-4 weeks after the infection and gradually decrease to lower levels during next several months. Given the early appearance and short lifespan of IgM antibodies, their detection is a marker of acute infection. The concentration of specific IgG antibodies increases slower, but they remain elevated for longer periods of time. Significant increase of level of specific IgG, even in the absence of IgM, indicates an active infection or reinfection. IgA antibodies are often detected in high titres in older patients, and may therefore be informative for the diagnosis of acute infection in adults.