PULMONARY DISEASE kansasii and M. intracellulare (Battey bacilli), the most virulent of this group of organisms, may produce tuberculosis like pulmonary disease in susceptible individuals, as rarely may the less virulent M. fortuitum, M. xenopei, and M. avium.Prevalence. In the United States and Europe, 1 to 2 percent of hospital admissions for tuberculosis is due to infection with either M. kansasii or M intracellulare. There are geographic variations, particularly in the United States.
The incidence of ofM. intracellulare infections are relatively high in Georgia and Florida, and M. kansasii infection is more frequent in Texas, Kansas, and Illinois. In some localities, the incidence is as high as 7 to 10 per of hospital admissions for tuberculosis.Epidemiology.The epidemiology of these in-infections is obscure. M. kansasii and M. intrasellar lare have been demonstrated in soil. Both organisms have been found in throat swabs and saliva of healthy individuals (in one report from Florida the incidence was as high as 14 percent). It is not known whether this transient carrier state is*ttecl from man to man or from some other, however, the person with the clinical disease not thought to transmit infection. as neither designation not yet formally recognized. overt disease nor the incidence of-•-deter-mined by use of a PPD prepared from the organism in question, is increased in family contacts. Skin testing surveys suggest a high incidence of sub-clinical infections in the endemic areas.
PULMONARY DISEASE Two-thirds of naval recruits from Georgia and Florida reacted to an M. intracellulare PPD, whereas only6 percent were positive to PPD-S (M. tuberculo-sis). Cross-reactions occur with PPD preparations from different mycobacteria but are generally weaker than reactions to the homologous PPD. Accordingly, simultaneous skin testing with several different PPD preparations can be used for diagnosis, assuming that the strongest reaction indicates the infecting organism. Data gathered in this fashion indicate a very high infection rate and low incidence of disease, illustrating the low virulence of these organisms for humans. Once the disease develops, pathologic changes are essentially the same as those found in tuberculosis. Clinical Manifestations. Pulmonary disease caused by M.kansasii and M.intracellulare is primarily a disease of white males over the age of 45; it is less frequent in females and in blacks of both sexes. Prior chronic bronchitis and emphysema have a definite predisposing influence, being present in 40 percent of patients with dis-ease due to M. kansasii and in 60 percent of those with disease due to M.intracellulare. Pneumoconiosis may increase susceptibility. Although virulence is less, disease, once established, tends to become cavitary and progressive. The clinical picture at any given time is indistinguishable from chronic pulmonary tuberculosis. Although in general slower in tempo than untreated tuberculosis, these infections may produce relentless destruction of pulmonary tissue and may lead to death from respiratory insufficiency. Constitutional symptoms such as fever, anorexia, weight loss, and wasting are much less prominent.
Local symptoms of cough and sputum are similar, and hemoptysis may occur somewhat more frequently than in tuberculosis. Roentgenographic studies usually reveal a process already far advanced at the time of discovery Cavities are more frequently thin-walled and pneumonic lesions less prominent than in tuberculosis, but there is much overlap, and roentgenographic differentiation is not possible in the individual case. Lesions have the apical posterior localization characteristic of tuberculosis. Pleural effusions are rare and pleural changes of any sort inconspicuous. Diagnosis is dependent upon bacteriologic identification of the specific organism. As mycobacteria other than M. tuberculosis may be found as a carrier state in the saliva, diagnosis of dis-ease requires repeated demonstration of the organisms in the presence of compatible pulmonary disease.
A tuberculosis-like disease that does not respond to antimicrobial therapy or the demonstration of a high order of primary drug resistance should suggest the possibility of one of the other mycobacterial species. Treatment. My mycobacteriosis differs most strikingly from tuberculosis in the conspicuous lack of susceptibility to the antituberculous drugs.