Aetiology and treatment of community-acquired pneumonia in adults: an historical perspective.

Community-acquired pneumonia is common. Most disease is mild but mortality among hospitalized patients is 5-20%. The most common aetiological pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and the 'atypical' organisms, Mycoplasma pneumoniae, Legionella pneumophila and Chlamydia pneumoniae. Less common pathogens account for 10-30% of cases and the aetiology cannot be determined in one-third to one-half of cases. Classification by aetiology and initiation of specific antimicrobial therapy are difficult and treatment is often initiated empirically. Ampicillin (or amoxycillin) or erythromycin are inexpensive and effective for most patients, but their use in combination, the addition of a beta-lactamase inhibitor (e.g. amoxycillin/clavulanate) or the substitution of an expanded spectrum cephalosporin (e.g. cefuroxime) should be considered for patients with more serious illnesses or pathogens likely to be drug-resistant. Fluoroquinolones such as ciprofloxacin or ofloxacin would be acceptable if adequacy for treating pneumococcal infections were likely. New macrolides, such as azithromycin and clarithromycin, and new fluoroquinolones, such as temafloxacin and sparfloxacin, have theoretical advantages over previously available drugs, but superior efficacy has not yet been demonstrated satisfactorily. Pneumococcal resistance in various parts of the world is modifying traditional treatment. Currently, there is no drug of choice for the empirical treatment of community-acquired pneumonia.