RATIO OF NUMBER OF PATIENTS WITH LUNG DISEASE DUE TO MYCOBACTERIUM AVIUM-M. INTRAGELLULARE COMPLEX AGAINST NUMBER OF PATIENTS WHO SHOWED CULTURE-POSITIVE SPUTUM SPECIMENS

Abstract

The ratio of the number of patients with lung disease due to Mycobacterium avium-M. intracellutare complex (M. avium complex) against the number of patients who showed positive cultures of acid-fast organism was estimated in the present study.
1. During the period of three years, 1978-1980, a total of 974 patients were hospitalized newly into the lung tuberculosis departments of the National Chubu Hospital. Out of these patients, 405 (41. 6%) were those showing positive cultures of acid-fast organisms, including Mycobacterium tuberculosis. The patients were examined for acid-fast organisms by 3 to 7 days examinations of the sputum specimen in the first month of the hospitalization. The acid-fast organisms isolated were tested for their growth on the Ogawa egg medium containing 0.5 mg/ml p-nitrobenzoic acid (PNB medium), and the organisms which did not grow on the PNB medium were regarded as M. tuberculosis (Tsukamura, M. and Tsukamura, S.: Tubercle, 45: 64-65, 1964). The acid-fast organisms which grew on the medium were identified according to the schedule previously described (Tsukamura, M.: Identification of mycobacteria, p.1-75, National Chubu Hospital, Obu, Aichi, Japan, 1975). The diagnosis of atypical mycobacteriosis was carried out according to the criteria of Tsukamura (Tsukamura, M.: Kekkaku, 53: 367-376, 1978). Of the patients hospitalized during the period of three years, a total of 38 patients were diagnosed as suffering from lung disease due to atypical mycobacteria (36, M. avium complex and 2, M. fortuitum).
The ratio of the patients with atypical mycobacteriosis was estimated as 3.9% of the patients newly hospitalized into the tuberculosis departments, and as 9.4% of the patients who showed positive cultures of acid-fast organisms (Table 1). The latter ratio was first estimated in the present study. The former ratio was higher than the ratio, 2.8%, estimated in nine hospitals of Japan in 1979.
2. The average age of 38 patients with atypical mycobacteriosis was higher than the average age of culture-positive tuberculous patients (Table 2). The average age of 77 patients with lung disease due to the M. avium complex, who were found in the above period and before, was also significantly higher than the average age of culture-positive tuberculous patients (Table 3).
3. From the ratios estimated in Table 1, the prevalence rate of lung disease due to M. avium complex in the Aichi prefecture was estimated as 2.36 or 2.34 per 10⁵ population per year (Table 4). The rate estimated in the Aichi prefecture wes higher than the rate, 1.30per 10⁵ population per year, which was estimated by the co-opeartive study for the whole country in 1979 (Tsukamura, M. et al.: Kekkaku, 56: 391-401, 1981).
4. The ratio of the number of patients, in whom acid-fast organism was observed in smear but was not isolated by culture, against the number of patients who showed positive cultures of acid-fast organism was estimated as 2.2%, and the ratio of that against the number of patients who showed acid-fast organism on smear was estimated as 3.2% (Table 5).