Drug resistance study of Mycobacterium tuberculosis in Canada, February 1,1993 to January 31, 1994

Objective: To estimate the prevalence of resistance of Mycobacterium tuberc ulosis to first-line, antituberculosis drugs in Canada Methods: M. tuberculosis isolates from one third of all culture-positive tu berculosis (TB) diagnosed between February 1, 1933 to January 31, 1994 in C anada were collected prospectively. Proportion of drug-resistant isolates a nd the factors related to drug resistance; were measured. Results: Of 458 study cases, 40 (8.7%) had: resistance to at least one firs t-line antituberculosis drug, of which 5.9% had mono-resistance, 0.7% had m ultidrug-resistance(MDR-TB) - i.e., resistance to at least isoniazid and ri fampin and 2.2% had other patterns. The overall prevalence of resistance am ong the foreign-born cases was 10.6% with the highest level among those who resided in Canada for less than four years (15.5%). Conclusions: Canada has a relatively low prevalence of antituberculosis dru g resistance; and a very low prevalence of MDR-TB. Some new immigrants to C anada may be nr higher risk for drug resistance and their initial treatment s needs to be tailored accordingly.