STUDIES ON LUNG DISEASE DUE TO ATYPICAL MYCOBACTERIA IN JAPAN-eport of the Study in 1979

The present study reports results of the study in 1979, which covered the period from April 1979 to March 1980. The study was restricted to patients hospitalized during this period, and out-patients were not subjected to the study. All patients who were considered to have lung disease due to myco-bacteria (including Mycobacterium tuberculosis) were studied for their sputum and clinical findings. All acid-fast organisms isolated were screened for atypical mycobacteria (mycobacteria other than M. tuberculosis) by p-nitrobenzoic acid-Ogawa egg medium. All mycobacterial strains other than M. tuberculosis were identified for their species in the National Chubu Hospital according to the methods previously described. For diagnosing lung disease due to atypical mycobacteria, modified criterion) of the criteria recently proposed by Tsukamura were used.<BR>1) Frequency of atypical mycobacteria among all mycobacteria (M. tuberculosis plus atypical mycobacteria) was estimated on patients hospitalized in June, September and December 1979 and March 1980 by monthly examinations. Ratio of atypical mycobacteria among all mycobacteria was estimated at 12.0% (Table 1). This ratio was 6.0%, 5.8%, 7.8% and 9.5% in 1971, 1974, 1975 and 1977, respectively. The increase in the ratio is considered as probably due to a relative increase of patients with disease due to atypical mycobacteria among hospitalized patients. The kind of species of atypical mycobacteria are shown in Tables 2 and 3. It was noticed that the ratio of M. nonchromo-genicum complex, which occur as casual isolates, decreased from 4.4% in 1971 to 0.4% in 1979.<BR>2) Number of patients with lung disease due to atypical mycobacteria found in this study year was 141. The kind of species which have caused disease are shown in Table 4. Although the disease due to M. kansasii appeared almost restrictively in Tokyo area until 1978, it has been shown in the pre-sent study that the disease has appeared also in Fukuoka and Osaka area (Fukuoka and Kinki Hos-pitals) (Table 4). Sex and age of patients are shown in Table 5. The ratio, (number of patients with lung disease due to atypical mycobacteria) / (average number of patients hospitalized in tuber-culosis departments per day), is increasing annually (Table 6).<BR>3) Prevalence rate of lung disease due to atypical mycobacteria was estimated using the data of statistics of tuberculosis of the Ministry of Health and Welfare, Japan, and the ratio, (number of patients with lung disease due to atypical mycobacteria found among newly hospitalized patients) / (number of patients newly hospitalized into tuberculosis departments), which was estimated during a period of the 1st January to the 31st December of every year (Tables 7 and 8). Prevalence rate of the disease appeared to be different from prefecture to prefecture. The prefectures locating in the South coast of the Pacific ocean, Tokyo, Aichi, Osaka and Kochi, showed a high prevalence rate, and those locating in North Japan a lower rate (Table 9; Fig.1). The prevalence rate in 1979 has been estimated at 1.6 per 10⁵ population per year (Table 10). In a previous paper13), we have reported that the prevalence rate is slightly increasing or almost the same, but the result of the present study suggested that the prevalence rate is probably the same since several years (Table 10). Increase of the ratio of patients with disease due to atypical mycobacteria among all hospitalized patients as ob-served in Table 6 is considered to be due to decrease of the prevalence rate of tuberculosis. The kind of species, which caused lung disease in 537 patients, who were found among 32, 293 newly hospitalized patients during period of January 1971 to December 1979 (9 years), are shown in Table 11.