Ambulatory Patients with CAP
The majority of the approximately 4 million cases of community- acquired pneumonia (CAP) in the United States are treated on an ambulatory basis, yet most of the literature studying CAP is based on inpatient data. The most recent recommendations of the American Thoracic Society indicate a macrolide or tetracycline for outpatient treatment of pneumonia in persons under age 60 without comorbidity, suggesting that although Streptococcus pneumoniae may be a frequent pathogen, organisms associated with what has been heretofore called "atypical" pneumonia (e.g., Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella) merit out pharmacologic attention. To define the etiologic balance and clinical course of outpatient pneumonia, this study was performed.
Patients with acute onset of pneumonia and radiographic confirmation (n = 149) were prospectively studied in Halifax, Nova Scotia. Microbiologic diagnoses were by acute/convalescent serum antibody levels to standard bacterial and viral etiologic agents. In the patients in whom an etiologic diagnosis was confirmed (74/149), Mycoplasma pneumoniae was responsible for 46%, Chlamydia pneumoniae for 21%, a combination of the two agents for 7%, and Coxiella burnetti for 5%. Streptococcus pneuoniae or Hemophilus influenzae was responsible for about 3% of cases.
Although there was a statistically significant difference in the frequency of chills, headache, and sweats between atypical pneumonia and the "other" patients in this study, the difference does not appear sufficiently discriminating to be of clinical utility. Based upon this study, the suggestion of a macrolide or tetracycline for empiric treatment of pneumonia appears well-founded.
Marrie T. Am J Med 1996;101: 508-515.
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