2012-05-19
Mycoplasma 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.
Mycoplasma pneumoniae
Mycoplasmas are poorly explored microorganisms. Infection is prevalent mostly among children and adolescent (5-15 years old). Source of the infection – sick or healthy infected with mycoplasma persons. This is an airborne infection, it spreads when person is coughing and sneezing. In drops saliva and sputum bacteria remain viable for a long time. Accessed into the airways bacteria invade cells of mucosa and start to reproduce. Chance of sicken of the mycoplasma infection depends on the body resistance. After recovery resistance to causative agent does not develop.
The most characteristic symptom of mycoplasma infection is dry and persistent cough. Bacteria can cause pharyngitis, inflammation of larynx and bronchi, otitis or sinusitis. When mycoplasma invades lungs it causes atypical (non-specific) pneumonia. Mycoplasma affects body slowly: patient may complain with weakness, fatigues, severe headache occurs, patient feels ticklish throat, and fever occurs. However, finding of hematology tests and x-ray examination are normal.
Relatively new molecular methods help to diagnose mycoplasma infection. Using molecular PCR method bacterium M. pneumoniae and its DNA are determined in a smear from nasopharynx. When blood is used for test, antibodies against M. pneumoniae are defined.
Scrapings from the posterior wall of pharynx are used for the test. Test duration is 2 days. Tests are performed on Mondays and Thursdays.