Bacteriophage types of Mycobacterium tuberculosis in the United States.

Strains of Mycobacterium tuberculosis from various geographic areas within the continental United States were typed according to their susceptibility to 4 mycobacteriophages. Of 462 wild isolates studied, 34% were phage type 1 (previously designated A0), 42% were type 2 (A1), 2.6% were type 5 (A4), 13% were type 7 (A6), and 20.1% were type 8 (B). Distribution of types was essentially unaffected by geographic location, sex, age, or ethnic origin of the patient or by resistance of the isolate to antituberculosis drugs. Major types were further divided by susceptibility of the strains to lysis by 8 auxiliary phages, 2 of which were phages newly evaluated in this study. A new numbering system is proposed for designating major phage types of M. tuberculosis.