2012-05-19
Chlamydia pneumoniae determination using PCR method
Causative agents of respiratory infections, Chlamydia pneumomniae and Mycoplasma pneumoniae, are localized in the respiratory tract and cause their damage; when they invade lungs they cause atypical (non-specific) pneumonia. Both causative agents are small intracellular organisms. These bacteria have only membrane instead of cell wall, and therefore they are able to live and reproduce only in the host cell using its energy.
Immune response to these bacteria (antibody production) is relatively slow and depends on the strength of body immune system. Early detection of these infections is based only on serologic methods (antibody detection in blood specimen), and it is not always conclusive. It is recommended to repeat test after 2-3 weeks and assess the changes of antibody titer. No immunity develops against these bacteria, one can be infected several times, and IgG antibodies for a long time persist in one’s blood. Because special media is required for the growth of these bacteria, it is impossible to grow them up using common bacteriological inoculation of the material from patient’s throat.
Relatively new molecular method, polymerase chain reaction (PCR) helps to diagnose M. pneumoniae and C. pneumoniae quickly and accurately. Using this method bacteria are identified directly though it’s DNA. Laryngeal smear (mucosa epithelium scraping) is sufficient specimen to perform PCR test. It is very important when children are examined because they are often afraid of blood collection procedure.
Chlamydia pneumoniae
C. pneumoniae differs from other chlamydia die to its protein composition and localization (usually it is localized in airway mucosa). It is an airborne infection. Infection agent may persist in the body for a long time and cause asymptomatic or chronic infection. There is evidence associating C. pneumoniae with atherosclerotic plaque, Alzheimer's disease, myocarditis, arthritis, neuritis and other diseases. However, it most often affects airways, causing dry cough, pharyngitis, laryngitis and sinusitis. C. pneumoniae causes approximately all community acquired pneumonias. Duration of incubation stage is approximately 1-2 weeks. Fever, headache and labored respiration may occur in acute period. Due to week immune response the most sensitive and specific diagnostic method is PCR, when bacterium itself is identified.
Scrapings from the posterior wall of pharynx are used for the test. Test duration is 2 days. Tests are performed on Mondays and Thursdays.