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.