Bacteriophage typing of strains of Mycobacterium tuberculosis from Nepal.

One hundred strains of Mycobacterium tuberculosis isolated from cases of pulmonary tuberculosis in Nepalese villagers were typed with the World Health Organization set of bacteriophages. The number of strains in the 3 major phage types A, I, and B were 19, 53, and 28 respectively. This distribution is significantly different from those described in other geographical regions. In particular there was a relatively low incidence of type A strains and, in common with South India, there was a high proportion of type I strains. All the strains in this study were resistant to 5-Furan-2 carbonic acid hydrazine and 34 were highly resistant to isoniazid. Representative strains of the 3 phage types, including 4 isoniazid-resistant type I strains, did not differ in their virulence in the guinea pig; thus the type I strains found in Nepal may not be of the same origin as those of this phage type from India which are usually attenuated in the guinea pig. This study provides further evidence for the existence of geographical differences in the types of tubercle bacilli.