ABSTRACT
Atypical organisms such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila are implicated in up to 40 percent of cases of community-acquired pneumonia. Culture is labor-intensive, takes several days to weeks for growth, and can be very insensitive for the detection of some of these organisms. Antibiotic treatment is empiric and includes coverage for both typical and atypical organisms.In the present study we investigate the occurrence Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila as atypical pathogens responsible for considerable cases of atypical pneumonia.Among 71 bronchoalveolar lavage specimens taken from patients presented clinically with community-acquired pneumonia admitted to Al-noor specialist Hospital Holly Makkah, KSA., PCR results showed that 14 cases [19.7%] gave positive results for Mycoplasma pneumoniae,16 cases [22.5%] gave positive results for Chlamydia pneumoniae and only 4 [5.6%] cases gave positive results for Legionella pneumophila. All our patients were living in an air conditioned atmosphere due to high temperature in the holly Makkah city. Two[2.8%] mortality cases from Legionella pneumophila were reported. Because of the non-specificity in clinical presentation of atypical pneumonia, specialized laboratory tests are necessary to establish the diagnosis. The PCR method is a rapid, sensitive and specific technique that has been applied to the detection of many infectious pathogens. Different PCR-based assays for the detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila in clinical specimens have been described