To estimate resistance rates of Mycobacterium tuberculosis to antituberculosis drugs in relation to previous treatment, country of origin, age and duration of residence in Canada.
Retrospective chart review of all culture-positive tuberculosis diagnosed between 1982 and 1994 in immigrants to Alberta.
A total of 753 immigrants with culture-positive tuberculosis were studied; 131 patients (17.4%, 95% Confidence Interval [CI] 14.7, 20.1) had strains resistant to one or more of the first-line medications (isoniazid [INH], rifampin [RIF], ethambutol [EMB], pyrazinamide [PZA], and streptomycin [SM]). Initial and secondary resistance rates were 16.4% and 30.3%, respectively (P = 0.003, Odds ratio [OR] 2.2, 95% CI 1.3, 3.8). Resistance occurred in 22.2% of patients 40 years of age and under, and in 13.8% of those over 40 years of age (P = 0.005, OR 1.8, 95% CI 1.2, 2.6). Resistant M. tuberculosis was isolated from 20.4% of those who had lived in Canada for less than 15 years, and in 9.0% of those who had immigrated to Canada more than 15 years before diagnosis (P