Atypical pathogens causing community-acquired pneumonia in adults.

OBJECTIVE To determine the frequency of community-acquired respiratory pathogens with special focus on atypical organisms in patients presenting to a tertiary care facility with community-acquired pneumonia (CAP). METHODS The descriptive study on adult patients was conducted from February 2007 to March 2008 at the Aga Khan University Hospital, Karachi. It comprised 124 consenting patients of age 16 and above who presentd with a diagnosis of community-acquired pneumonia. The diagnostic modalities used were based on significant changes in antibody titer or persisting high antibody titers in the case of Mycoplasma pneumoniae and Chalmydia pneumoniae infections, or bacterial antigen in urine, in the case of Legionella pneumophila serogroup 1 infection. Pyogenic bacteria were identified on the results of respiratory secretions or blood cultures. Continuous data and categorical variables were worked out using SPSS version 15. RESULTS Among the 124 patients enrolled, an etiologic agent was identified in 44 (35.4%) patients. The most common organism was Mycoplasma pneumoniae (n = 21, 17%), followed by Chlamydia pneumoniae (n = 15, 12%), Streptococcus pneumoniae (n = 9, 7%), Haemophilus influenzae (n = 2, 1.6%), Klebsiella pneumoniae (n = 2, 1.6%) and Staphylococcus aureus (n = 1, 0.8%). Streptococcus pneumoniae was the most common organism isolated from blood cultures. No cases of Legionella pneumophila serogroup 1 were identified. CONCLUSIONS Mycoplasma pneumoniae and Chalmydia pneumoniae are significant etiologic agents for community-acquired pneumonia occurring in Karachi. Local treatment guidelines for community-acquired pneumonia should include therapy directed specifically at these agents.