Community-acquired pneumonia in adults: Guidelines for management

Lower respiratory tract infections are the major cause of death due to infectious diseases in the United States. Despite substantial progress in detection of pathogens and in therapeutic options, there continue to be major controversies in the clinical management of these infections. This document represents the guidelines of the Infectious Diseases Society of America. The guidelines are applicable only to immunocompetent adult patients with community-acquired pneumonia. Diagnostic studies: The document provides recommendations for the evaluation of patients with suspected pneumonia, including the pivotal role of chest radiography to confirm the presence of a parenchymal infiltrate. Prognostic factors are defined, including indications for hospitalization. Many of the decisions to hospitalize patients are influenced by analyses from the Pneumonia Patient Outcomes Research Team, which have now been validated in clinical practice. Recommended diagnostic studies include blood cultures and gram staining and cultures of expectorated sputum for patients who require hospitalization. Caveats in this recommendation address the need for pretreatment specimens that are expeditiously transported and undergo cytologic screening as contingencies for optimal results. Tests for the presence of Legionella species, preferably culture and urinary antigen assay, should be performed for a subset of patients. Other diagnostic tests for specific microbial pathogens are recommended, but these tests are not considered routine. Some organisms are considered diagnostic as the cause of pneumonia when detected in any specimen; most potential pathogens recovered from expectorated sputum represent possible contaminants from the upper airways; thus interpretation of their recovery is dependent on clinical correlations, gram stain findings, and quantification in cultures. Selected topics are discussed individually as well as within the context of the broader perspective of all patients with pneumonia. These topics include pneumococcal pneumonia; aspiration pneumonia, pneumonia caused by anaerobic bacteria, Chlamydia pneumoniae, Legionella species, and Mycoplasma pneumoniae; Hantavirus pulmonary syndrome; Pneumocystis carinii pneumonia; influenza; and empyema. Treatment: Therapeutic recommendations are provided in two categories. The first category includes the recommendations that apply when a pathogen is detected, i.e., pathogen-directed therapy based on in vitro susceptibility test results and/or clinical trials. Penicillin or amoxicillin are recommended for strains of Streptococcus pneumoniae that show susceptibility or intermediate resistance (MIC, ≤ 1.0 μ/mL). For strains with high-level resistance (MIC, ≤2 μ/mL), the recommendation is based on results of in vitro testing; for empirical use, a fluoroquinolone with good antipneumococcal activity or vancomycin is recommended. Other microbe-specific recommendations are based on predicted in vitro activity and results of clinical trials or clinical experience. The second category of treatment recommendations applies when no etiologic diagnosis has been made and decisions on empirical antibiotic therapy are required. For this group of patients, the guideline provides multiple options because of the lack of clinical trial data that clearly identify superior regimens and the desire to encourage use of a broad range of drugs. The recommendations for outpatients are a macrolide, a fluoroquinolone with good activity against S. pneumoniae, or doxycycline. The recommendation for hospitalized patients is a β-lactam (cefotaxime, ceftriaxone, or a β-lactam-β-lactamase inhibitor) with or without a macrolide; an equally acceptable option is a fluoroquinolone with good antipneumococcal activity and established efficacy for atypical pneumonia (pneumonia due to Legionella species, C. pneumonia, or M. pneumonia). For seriously ill patients, emphasis is placed on adequate coverage for S. pneumoniae and, less commonly, Legionella species as the major causes of lethal pneumonia. The recommendations for empirical therapy are for a β- lactam combined with erythromycin, azithromycin, or a fluoroquinolone. However, the Panel recognizes that local factors such as susceptibility patterns an epidemiologically important pathogens may dictate alternative options. Therapy with parenteral agents usually may be changed to oral antimicrobial treatment, and patients can be discharged from the hospital when there is evidence of a clinical response and ability to tolerate oral medications. The recommended duration of treatment for pneumococcal pneumonia is 72 hours after the patient becomes afebrile. Most other forms of pneumonia caused by bacterial pathogens are treated for 1-2 weeks after patients become afebrile. Atypical pneumonia is usually treated for 10-21 days. Response: Failure to respond is ascribed to multiple factors, but most commonly represents inadequate host defense; less common causes include erroneous drug selection, dosage regimen, or diagnosis; an unusual pathogen; or dual infections or complication such as empyema. Diagnostic options in such cases include CT imaging, bronchoscopy, and diagnostic studies for alternative diagnoses. Prevention: The recommendations also address the important role of prevention, with major emphasis on guidelines for proper use of influenza and S. pneumoniae vaccines.