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Antituberculous drug resistance in Manitoba from 1980 to 1989
R Long1, J Manfreda, L Mendella
1Department of Medicine, University of Manitoba, Winnipeg.
Objectives:
To estimate the magnitude of antituberculous drug resistance and identify the risk factors for its development in tuberculosis patients in Manitoba over a 10-year period. As well, to examine the clinical course of the patients whose initial or subsequent isolates of Mycobacterium tuberculosis were resistant to one or more drugs.
Design:
Comparison of drug-resistant and non-drug-resistant cases of tuberculosis.
Setting:
Manitoba.
Patients:
All people with tuberculosis reported to the Central Tuberculosis Registry of Manitoba between Jan. 1, 1980, and Dec. 31, 1989.
Main Outcome Measures:
Of 1478 cases of active tuberculosis 1086 were culture positive, and drug susceptibility testing was performed in these cases. The clinical course, including outcome of treatment, of all drug-resistant cases was described.
Results:
Of 1086 culture-positive cases of tuberculosis 77 (7.1%) were drug resistant. Odds ratios suggested that the risk of drug resistance was significantly higher among the immigrants than among the other Canadians. Compared with the other Canadians the risk of drug resistance was 9.9 times greater among the immigrants in whom tuberculosis developed within the first year after arrival in Canada and 5.4 times greater among the immigrants in whom it developed 2 to 5 years after arrival in Canada. Of the 71 patients with drug-resistant disease whose type of resistance was known 62% had never taken antituberculous drugs before and 38% had. Most (91%) of the 77 cases of drug-resistant disease were resistant to first-line drugs, especially isoniazid and streptomycin. Thirty-two (42%) of the 77 cases were resistant to two or more first-line drugs. Of patients with drug-resistant disease a subgroup of 10 had disease that became resistant to several drugs over the 10-year period. The outcome of treatment in these individuals was poor, and they presented a particular public health problem.
Conclusion:
Resistance to one or more first-line antituberculous drugs continues to complicate the treatment of tuberculosis and may facilitate the spread of the disease.