Abstract
ObjectivesCompare the molecular epidemiology of tuberculosis (TB) between two large Canadian provinces–Ontario and British Columbia (BC)–to identify genotypic clusters within and across both provinces, allowing for an improved understanding of genotype data and providing context to more accurately identify clusters representing local transmission.DesignWe compared 24-locus Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) genotyping for 3,314 Ontario and 1,602 BC clinical Mycobacterium tuberculosis isolates collected from 2008 through 2014. Laboratory data for each isolate was linked to case-level records to obtain clinical and demographic data.ResultsThe demographic characteristics of persons with TB varied between provinces, most notably in the proportion of persons born outside Canada, which was reflected in the large number of unique genotypes (n = 3,461). The proportion of clustered isolates was significantly higher in BC. Substantial clustering amongst non-Lineage 4 TB strains was observed within and across the provinces. Only two large clusters (≥10 cases/cluster) representing within province transmission had interprovincial genotype matches.ConclusionWe recommend expanding analysis of shared genotypes to include neighbouring jurisdictions, and implementing whole genome sequencing to improve identification of TB transmission, recognize outbreaks, and monitor changing trends in TB epidemiology.
Highlights
Tuberculosis (TB) remains a major public health issue in Canada
This study describes the first comprehensive interprovincial comparison of MIRU-VNTR genotyping in Canada using >4,900 Mycobacterium tuberculosis (Mtb) isolates collected in Ontario and British Columbia (BC) over a seven-year period
While there was minimal evidence of cross-jurisdictional transmission in the present study, the comparison of TB molecular epidemiology between Ontario and BC furthered our understanding of local transmission and latent TB infection (LTBI) reactivation by providing context to the genotypes observed in each province
Summary
Tuberculosis (TB) remains a major public health issue in Canada. Molecular techniques, such as 24-locus Mycobacterial Interspersed Repetitive Units–Variable Number Tandem Repeat (MIRU-VNTR) genotyping, have improved understanding of TB epidemiology, and many jurisdictions are adopting routine genotyping of all Mycobacterium tuberculosis (Mtb) isolates [1,2,3]. TB incidence rates in Ontario and BC are nearly identical, with 4.5 and 4.6 cases per 100,000 population respectively [7] Together, these two provinces represent a substantial burden of disease in Canada, accounting for >50% of the nation’s TB cases, with rates in both settings largely driven by reactivation of latent TB infection (LTBI) in persons born outside Canada [4]. These two provinces represent a substantial burden of disease in Canada, accounting for >50% of the nation’s TB cases, with rates in both settings largely driven by reactivation of latent TB infection (LTBI) in persons born outside Canada [4] Both provinces are popular destinations for immigrants, with the multi-cultural cities of Toronto and Vancouver attracting many newcomers [8]. This is true in BC, where under-housed migrants from other provinces–some of whom are experiencing mental illness, addictions, and/or chronic health conditions [10,11]–are thought to be attracted to Vancouver by the temperate climate
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