Widespread dissemination of a drug-susceptible strain of Mycobacterium tuberculosis

In New York City, a large proportion of new tuberculosis cases has been caused by 1 drug-susceptible strain (called C strain) of Mycobacterium tuberculosis, Between 1991 and 1994, among >600 tuberculosis patients consecutively identified in four large hospitals in the city, 54 with C strain, 69 with non-C Cluster pattern strains, and 42 with noncluster pattern strains were studied, Susceptibility to reactive nitrogen intermediates (RNI) of selected isolates was compared, In a case-control analysis, 51% of patients with C strain, 28% with non-C cluster strains (P<.05), and 14% with noncluster strains (P<.01) were found to be injection drug users, C strain but not 13 other unrelated isolates were resistant to RNI, Injection drug use may provide a selective pressure for an RNI-resistant tubercle bacillus to emerge, which may give the organism a biologic advantage and explain the widespread dissemination of C strain M. tuberculosis within the city.