The combination of community-acquired pneumonia (CAP) and influenza ranks as the sixth leading cause of death in the United States. The crude rate of these two conditions has increased by almost 60 percent in the past 15 years, making CAP a rapidly growing health risk, particularly among the elderly. Most cases of CAP are caused by Streptococcus pneumoniae, with an expanding list of other etiologic agents, including Haemophilus influenzae and Chlamydia pneumoniae. Unfortunately, an etiologic agent is never identified in up to 60 percent of patients with CAP. If no pathogen is identified, the diagnosis must be made on the basis of clinical criteria alone, none of which is definitive. In the past, the American Thoracic Society (ATS) and the Infectious Disease Society of America (IDSA) established evaluation and treatment guidelines for patients with CAP. Recently, however, IDSA proposed new guidelines based on the changing pattern of etiologic agents in an effort to streamline patient evaluation and identification of the associated etiologic agent. Bernstein summarizes these recommendations.

The new IDSA guidelines emphasize identification of the pathogen responsible for CAP. The new algorithm begins with obtaining a thorough history, including identification of symptoms consistent with CAP, such as a cough, fever and a prior history of pneumonia. Additional risk factors, including a history of viral infections, immunosuppression, neutropenia and pulmonary edema, also need to be identified at this time. The next step is obtaining a chest radiograph to establish the diagnosis and provide a baseline to assess trends in the patient's condition. Additional diagnostic studies include Gram stain and culture of sputum, a complete blood count including differential and a comprehensive metabolic profile. Severely ill patients should also be tested for tuberculosis and Legionella disease.

Guidelines for empiric treatment of CAP continue to evolve. IDSA now recommends macrolides, doxycycline or fluoroquinolones for primary therapy, as each of these agents is effective against the primary pathogen and many others. Therapy for patients with severe pneumonia should include fluoroquinolones, erythromycin or azithromycin, supplemented with cefotaxime, ceftriaxone or a beta-lactam/beta-lactamase inhibitor. Hospitalized patients can usually be switched from intravenous to oral therapy within three days. The total course of treatment in patients with CAP caused by Streptococcus pneumoniae should be seven to 14 days or until the patient has been afebrile for 72 hours. In patients with atypical pathogens, treatment should continue for 10 to 21 days.

The author concludes that the new IDSA guidelines cover all aspects of patient management. Greater emphasis is placed on obtaining a thorough history and a comprehensive battery of diagnostic tests, particularly sputum cultures, to guide therapy. Recommendations for antibiotic therapy include specific agents that have been proved effective against a variety of pathogens. The new IDSA guidelines are currently being integrated with revised guidelines from ATS to establish a single set of recommendations for the evaluation and treatment of CAP.