肺非定型抗酸菌症の発症要因

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The incidence (development) of lung disease due to mycobacteria other than tubercle bacilli is influenced by the following factors: (1) Ecology of mycobacteria (geographic distribution of mycobacteria); (2) virulence of mycobacteria; (3) general and local conditions of the host. Ecological distribution of mycobacteria differs from area to area in the world (Tsukamura, M. Kekkaku, 52: 319, 1977). In the United States and Europe, disease due to M. kansasii occupies more than one half of the total diseases, whereas, in Japan and Australia, the disease remains only a few percentages and disease due to M. avium-intracellulare occupies the majority. Such probable geographic difference of the distribution of mycobacteria is believed to be influencial on the mode of incidence of the disease. In Europe where M. kansasii lives abundantly in the environment, dusty work may accelarate the infection of this organism. However, in other countries where M. kansasii occurs rarely, the same condition does not always cause the disease. Furthermore, the morbidity of tuberculosis also may influence the incidence of mycobacterioses due to mycobacteria other than tubercle bacilli. The incidence of disease is considered to be related with the host-parasite relationship, where the virulence of the parasite and general and local host conditions are important. The virulence is different according to the mycobacterial species, but there is an evidence that the serotype of M. intracellulare may be correlated with the virulence (Tsukamura, M. et al.: Jap. J. Microbiol., 18: 271, 1974). There are not a few papers concerning with the general condition of the host. For example, decrease of resistance (immunity) by aging may influence the incidence of the disease. Local conditions of the host are considered to be important. The occurrence of chronic obstructive pulmonary disease has been reported to be important factors by many authors. Dusty environment also has the same effect, as it is suggested to decrease the clearance of air ways. As the chronic obstructive lung disease, emphysema, bronchiectasis and asthma, seem to be important in the Unite States, whereas lung tuberculosis in which cavitary lesions remain after negative conversion seems to be more important in Japan (Table 1). This specific condition in Japan is probably due to two factors: (1) higher morbidity of tuberculosis and (2) sufficient care (chemotherapy and hospitalization) of tuberculosis patients by the tuberculosis control law. The existence of chronic cavitary lesions due to tuberculosis, in which negative conversion has occurred, provides the same condition as the presence of obstructive diseases. In fact, infection of post-tuberculous cavities with M. intracellulare is reported in Japan (Tsukamura, M.: Amer. Rev. Resp. Dis., 108: 679, 1973; Co-operative Study Group of Japanese National Chest Hospitals: Kekkaku, 51: 41, 447, 1976). The presence of chronic obstructive disease provides a favorouble condition for transient multipli cation of the organisms (Tsukamura, M.: Amer. Rev. Resp. Dis., 108: 679, 1973). Occurence of further multiplication of the organisms will be correlated with general condition of the host. In summary, local condition of the host is corelated to the transient multiplication (colonization) of the organism and general condition to further development of the disease.
日本結核病学会の論文

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束村道雄
国立療養所中部病院

肺非定型抗酸菌症の発症要因

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