Community-acquired pneumonia: an update

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Despite the discovery of new pathogens and the evolving problem of antibiotic resistance, the basic trends in community-acquired pneumonia remain remarkably constant. This article reviews the common pathogens, new pathogens, their clinical presentations, the diagnostic workup, the decision to hospitalize, antibiotic resistance, and antibiotic choices.


Streptococcus pneumoniae is still the most common causative organism in community-acquired pneumonia (CAP). Routine microbiologic testing is not mandatory in otherwise healthy outpatients with CAP not requiring hospitalization. We do favor obtaining sputum Gram's stains, sputum cultures, and blood cultures in patients requiring hospital admission. The possibility of underlying human immunodeficiency virus (HIV) infection should be considered in young patients with bacteremic S pneumoniae or S pneumoniae pneumonia. Empiric outpatient therapy with erythromycin will often suffice for relatively healthy patients, but sicker patients may need testing, hospitalization, and parenteral therapy. In critically ill patients, in those with recognized risk factors for penicillin resistance, or in geographic areas with known endemic resistant S pneumoniae, vancomycin is the empiric drug of choice for patients with suspected S pneumoniae pneumonia. Once antibiotic susceptibilities are identified, patients should be switched to penicillin if the isolate is sensitive.



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