| Summary: | Population-based molecular epidemiologic studies of tuberculosis have been widely performed to assess the burden of ongoing TB transmission within a population. By genotyping M. tuberculosis isolates (M.TB), cases with matching DNA "fingerprints" are inferred to be due to ongoing transmission, and those with non-matching or "unique" fingerprints are inferred to represent re-activation disease. Two population-based molecular epidemiologic studies using three genotyping methods (IS6110 RFLP, spoligotyping and MIRU) are presented here. The first study examines all TB cases among the Inuit community if Nunavik, Quebec (1990-2000). Our analysis identified previously unrecognized inter-village transmission and estimated that at least 65% of TB cases were due to ongoing transmission. The second study is a case-control study that examines a pyrazinamide-resistant (PZA-R) M.TB strain present in the Canadian-born population (1990-2000). We observed that 77 PSA-R TB cases shared a common mutation conferring the PZA resistance. In this low-incidence setting, the cases were most likely due to reactivation from a common but old PZA-R M.TB strain in the absence of significant ongoing transmission. In contrast to the Inuit case-study where 76% of cases had matching genotypes across all three modalities, only 19% of PZA-R cases and 13% of Canadian-born controls were clustered by the same analysis. The utility of cluster analysis in the understanding of the transmission patterns of TB in these two different populations are compared and discussed.
|
|---|