Unclassified mycobacteria isolated from human suspect tuberculosis cases in New-foundland: preliminary studies on fifteen strains.

Unclassified mycobacteria were isolated from 36 of 35,555 clinical specimens cultured for M. tuberculosis. The majority of isolations were from patients suspected of having tuberculosis and from whom repeat attempts at culture failed to yield typical tubercle bacilli. Fifteen strains thus far studied were not capable of causing generalized tuberculosis in guinea pigs, and all were highly resistant to the commonly employed antituberculous therapeutic agents. Eleven of the 15 strains were resistant to 100 or more mug./ml. of streptomycin; 12 strains were resistant to 25 or more mug./ml. of para - aminosalicylic acid; and all 15 showed growth in the presence of 50 or more mug./ml. of isoniazid. All strains were niacin-negative and catalase-positive. In the absence of other cultural findings, isolation of anonymous mycobacteria poses a major problem, especially in those cases in which the clinical and radiographic findings are typically those of tuberculosis.