COMMUNITY-ACQUIRED PNEUMONIA IN ADULTS

Although the frequency of community-acquired pneumonia caused by Strep tococcus pneumoniae continues to be high, studies show that Mycoplasma pneumoniae, Chlamydia pneumoniae, or Legionella pneumophila are the e tiologic agents in 20% to 40% of community-acquired pneumonia in adult s. The clinical presentation of pneumonia caused by these organisms ma y be indistinguishable from pneumonia due to S pneumoniae. Separation of cases of pneumonia due to S pneumoniae as typical and that caused b y M pneumoniae, C pneumoniae, or L pneumophila as atypical is unwarran ted and unhelpful in planning therapy. As many as 35% to 50% of patien ts do not have an etiologic agent identified. Community-acquired pneum onia can have high morbidity and mortality in patients who are older, have underlying lung disease, diabetes mellitus, or other comorbid con ditions, or who have decreased immune function regardless of the speci fic etiologic agent. In choosing appropriate empiric antimicrobial the rapy in hosts who are not immunocompromised, erythromycin and other, m acrolide antibiotics have the advantage of being effective against a w ide range of pathogens likely to be encountered, including S pneumonia e, M pneumoniae, and L pneumophila, and of having some benefit against C pneumoniae. In other patients, the selection of antibiotic therapy can be based on age, clinical suspicion, epidemiologic data, and labor atory test results. Antimicrobial therapy can be directed at specific organisms when and if they are identified.