Multicenter surveillance of adult atypical pneumonia in Japan: its clinical features, and efficacy and safety of clarithromycin.

A prospective multicenter study involving 156 Japanese medical institutions was conducted to clarify the clinical features of adult atypical pneumonia and the efficacy and safety of clarithromycin. Atypical pneumonia was suspected in 730 patients according to the Japanese Respiratory Society's Guidelines for the Management of Community-Acquired Pneumonia in Adults, and clarithromycin was administered. On the basis of bacteriological and serological tests, 465 patients were diagnosed with atypical pneumonia. Mycoplasma pneumonia was common among younger patients and chlamydia pneumonia among older patients. Underlying respiratory disease was uncommon among mycoplasma patients but prevalent among chlamydia patients. According to the severity classification given in the abovementioned guidelines, most mycoplasma patients had mild infection, whereas a high percentage of chlamydia patients had moderate infections. Body temperature was higher and coughing more severe in the mycoplasma patients than in the chlamydia patients. On the other hand, intergroup differences were not observed regarding extent of lung shadowing on plain radiographs, peripheral white blood cell count, or C-reactive protein (CRP). The effectiveness of clarithromycin was 96.8% in mycoplasma patients (153/158), 92.9% in chlamydia patients (78/84), and 96.0% in the group comprising all atypical pneumonia patients, including those with superinfection (288/300). The incidence of adverse drug reactions was 3.4% (24/698). Macrolide resistance in Mycoplasma pneumoniae has been reported in Japan, but the results of this surveillance study showed that clarithromycin is effective in treating adult atypical pneumonia.