Atypical mycobacterial infections: a clinical study of 92 patients

Between July 1970 and December 1979, 92 patients with atypical mycobacterial infections of the lung were hospitalized 110 times at Blue Ridge Hospital (Charlottesville, Va). These patients comprised less than 3% of all patients hospitalized for active mycobacterial disease. Sixteen had Mycobacterium kansasii or group I disease, three had group II disease (two M scrofulaceum, one M szulgai), 70 had group III disease (68 M avium-intracellulare, two M xenopi), and three had M fortuitum or group IV disease. M kansasii infections comprised 23% of the total during the first five years, but only 6% during the second half of the decade. Clinical and roentgenographic findings were similar to those in patients with tuberculosis. As anticipated, most of the M kansasii organisms were sensitive to antimycobacterial drugs, and these patients generally responded well to chemotherapy. In contrast, most of the group III organisms, including one of the M xenopi, exhibited resistance to several drugs. Despite the high incidence of resistance, 59% of the patients with group III infections who were treated for at least three months in the hospital had sputum cultures converted to negative.