Abstract
SettingNationwide Canadian public health surveillance.ObjectiveDescription of demographic features and disease characteristics of drug-resistant tuberculosis (TB) in Canada over a 12 year period.DesignContinuous surveillance of all cases of culture-confirmed TB in Canada. Demographic and microbiologic features were analyzed and comparisons between drug-susceptible, multidrug-resistant (MDR), and drug-resistant not-MDR were made. Cases of extensively drug resistant TB are described.Results15,993 cases of culture-confirmed TB were reported during the study period. There were 5 cases of XDR-TB, 177 cases of MDR-TB, and 1,234 cases of first-line drug resistance not-MDR. The majority of drug-resistant cases were reported in foreign-born individuals, with drug-resistant cases diagnosed earlier post-arrival in Canada compared to drug-susceptible cases. In MDR-TB isolates, there was a high rate of drug-resistance to other first- and second-line drugs, making reliable empiric therapeutic recommendations for MDR-TB difficult. There was a statistically significant association between both MDR and drug-resistance not-MDR, and the risk of a negative treatment outcome (defined as treatment failure, absconded, or treatment ongoing >3 yrs).ConclusionDrug-resistance complicates TB management even in developed nations with well-established TB control programs. The predominantly international origin of drug-resistant cases highlights the need for global strategies to combat TB.
Highlights
Multidrug-resistant tuberculosis (MDR-TB), defined as TB resistant to both isoniazid (INH) and rifampicin (RIF), complicates TB control efforts by requiring prolonged treatment with drugs that are less potent, more costly and more toxic than standard INH and RIF-based regimens [1,2]
Rather than use standardized treatment regimens based on population surveys of local drug susceptibility tests (DSTs) patterns, TB control programs in Canada use second-line drug susceptibility testing to design individualized treatment regimens, minimizing the amplification of resistance and sparing patients from potentially unnecessary toxic drugs
This represents 78% of all TB cases reported during the study period
Summary
Multidrug-resistant tuberculosis (MDR-TB), defined as TB resistant to both isoniazid (INH) and rifampicin (RIF), complicates TB control efforts by requiring prolonged treatment with drugs that are less potent, more costly and more toxic than standard INH and RIF-based regimens [1,2]. In countries performing second-line drug susceptibility testing on MDR-TB isolates, 5.4% of MDR-TB cases were found to be XDR-TB [3]. In Canada, each province and territory has local and/or reference laboratory capacity for isolation of Mycobacterium tuberculosis complex and performance of first- and second-line drug susceptibility tests (DSTs). Rather than use standardized treatment regimens based on population surveys of local DSTs patterns, TB control programs in Canada use second-line drug susceptibility testing to design individualized treatment regimens, minimizing the amplification of resistance and sparing patients from potentially unnecessary toxic drugs
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