Dominant Mycobacterium tuberculosis Lineages in Elderly Patients Born in Norway

Abstract

BackgroundDuring the previous century Norway had a high incidence of tuberculosis, but no molecular epidemiological studies could be performed and these previously epidemic strains have been disappearing during the last decades. Currently, tuberculosis among native Norwegians is in the elimination phase, and it is still not known what type of M. tuberculosis was so efficiently controlled during the second half of the 20th century. However, many elderly Norwegian-born people still develop TB that cannot be clustered to imported or recently transmitted strains of M. tuberculosis. Thus, the majority of these cases are results of reactivation of disease that was transmitted many decades ago.Methodology/Principal FindingsA total of 213 strains of M. tuberculosis isolated during 1998–2005, from patients born in Norway before 1950 were genotyped in the current study. The findings demonstrated a highly homogenous M. tuberculosis population among the patients. A total of 40% belonged to the T-family, were 35% were assigned to T1 sub- family (T2 = 0, 93%, T3 = 1, 4% and T4 = 2, 3%). As many as 35% of the isolates belonged to the Haarlem family, were 15% were assigned to Haarlem1 and 19% to Haarlem3. The remaining 25% belonged to 15 different other families. The RFLP-patterns indicated that the isolates were not a result of recent transmission, but rather represented well established strains that apparently dominated in Norway many decades ago.Conclusions/SignificanceThe T 1, Haarlem 1, and Haarlem 3 families of M. tuberculosis were abundant among patients born in Norway before 1950. The M. tuberculosis cases represented reactivated disease that had been acquired before 1994 and were likely to have been latent for several decades. Thus, the current study indicated that the T 1, Haarlem 1, and Haarlem 3 families may have been common in Norway, when tuberculosis represented a serious public health threat during the first half of the 20th century.

Mycobacterium tuberculosis Strains Potentially Involved in the TB Epidemic in Sweden a Century Ago

“…This high prevalence of modern H, T and LAM strains is similar to the prevalence among isolates from patients born before 1950 in Norway, where a total of 40% of 213 isolates belonged to the T family and 35% to the H family [23]. As the Norwegian study, our study only included isolates displaying RFLP patterns not previously present in our database indicating an unlikely recent transmission.…”

Molecular Epidemiology of Tuberculosis in Finland, 2008-2011

“…Additionally, Finland – and other Nordic countries- had endured a very high tuberculosis incidence before the second world war [1]. As reported from Sweden and Norway, certain lineages (Haarlem and T) were predominately found among elderly cases, suggesting that these lineages were most likely associated with the epidemic during the first half of the 20 th century [15,16]. As found in this study, Haarlem and T were also the most common lineages found among Finnish born TB cases.…”

Clustering of Tuberculosis Cases Based on Variable-Number Tandem-Repeat Typing in Relation to the Population Structure of Mycobacterium tuberculosis in the Netherlands

“…Among nonclustered native Dutch TB cases, Euro-American lineages were most frequently isolated. Domination of these lineages among native TB cases has also been shown in other European populations (19,20), suggesting that these lineages have been circulating in Europe for centuries (21). In contrast, recentimmigrant cases caused by nonclustered non-Euro-American strains originated from distant geographical areas.…”