Clustered tuberculosis in a low-burden country: nationwide genotyping through 15 years.
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.
International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark. Kamper-Jørgensen, zazakj@me.com
Z
Z
Kamper-Jørgensen
A B
AB
Andersen
A
A
Kok-Jensen
I C
IC
Bygbjerg
P H
PH
Andersen
V O
VO
Thomsen
M
M
Kamper-Jørgensen
T
T
Lillebaek
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D012150:Polymorphism, Restriction Fragment Length; D012189:Retrospective Studies; D014376:Tuberculosis / Q000453:epidemiology* / Q000382:microbiology*; D055815:Young Adult
D004251:DNA Transposable Elements; D004269:DNA, Bacterial