Clustered tuberculosis in a low-burden country: nationwide genotyping through 15 years

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Molecular genotyping of Mycobacterium tuberculosis has proved to be a powerful tool in tuberculosis surveillance, epidemiology, and control. Based on results obtained through 15 years of nationwide IS6110 restriction fragment length polymorphism (RFLP) genotyping of M. tuberculosis cases in Denmark, a country on the way toward tuberculosis elimination, we discuss M. tuberculosis transmission dynamics and point to areas for control interventions. Cases with 100% identical genotypes (RFLP patterns) were defined as clustered, and a cluster was defined as cases with an identical genotype. Of 4,601 included cases, corresponding to 76% of reported and 97% of culture-verified tuberculosis cases in the country, 56% were clustered, of which 69% were Danes. Generally, Danes were more often in large clusters (= 50 persons), older (mean age, 45 years), and male (male/female ratio, 2.5). Also, Danes had a higher cluster frequency within a 2-year observation window (60.8%), and higher clustering rate of new patterns over time, compared to immigrants. A dominant genotype, cluster 2, constituted 44% of all clustered and 35% of all genotyped cases. This cluster was primarily found among Danish males, 30 to 59 years of age, often socially marginalized, and with records of alcohol abuse. In Danes, cluster 2 alone was responsible for the high cluster frequency level. Immigrants had a higher incidence of clustered tuberculosis at a younger age (0 to 39 years). To achieve tuberculosis elimination in Denmark, high-risk transmission environments, like the cluster 2 environment in Danes, and specific transmission chains in immigrants in the capital area, e.g., homeless/socially marginalized Somalis/Greenlanders, often with alcohol abuse, must be targeted, including groups with a high risk of reactivation.
Original languageEnglish
JournalJournal of Clinical Microbiology
Issue number8
Pages (from-to)2660-2667
Number of pages8
Publication statusPublished - 2012

    Research areas

  • Adolescent, Adult, Aged, Aged, 80 and over, Child, Child, Preschool, Cluster Analysis, DNA Transposable Elements, DNA, Bacterial, Denmark, Female, Genotype, Humans, Infant, Infant, Newborn, Male, Middle Aged, Molecular Epidemiology, Molecular Typing, Mycobacterium tuberculosis, Polymorphism, Restriction Fragment Length, Retrospective Studies, Tuberculosis, Young Adult

ID: 44258367