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Troels Lillebaek

Publications and source records attributed to Troels Lillebaek.

16 recordsLinked to original sources
PubMed2006

Mycobacterium tuberculosis complex genetic diversity: mining the fourth international spoligotyping database (SpolDB4) for classification, population genetics and epidemiology.

BACKGROUND: The Direct Repeat locus of the Mycobacterium tuberculosis complex (MTC) is a member of the CRISPR (Clustered regularly interspaced short palindromic repeats) sequences family. Spoligotyping is the widely used PCR-based reverse-hybridization blotting technique that assays the genetic diversity of this locus and is useful both for clinical laboratory, molecular epidemiology, evolutionary and population genetics. It is easy, robust, cheap, and produces highly diverse portable numerical results, as the result of the combination of (1) Unique Events Polymorphism (UEP) (2) Insertion-Sequence-mediated genetic recombination. Genetic convergence, although rare, was also previously demonstrated. Three previous international spoligotype databases had partly revealed the global and local geographical structures of MTC bacilli populations, however, there was a need for the release of a new, more representative and extended, international spoligotyping database. RESULTS: The fourth international spoligotyping database, SpolDB4, describes 1939 shared-types (STs) representative of a total of 39,295 strains from 122 countries, which are tentatively classified into 62 clades/lineages using a mixed expert-based and bioinformatical approach. The SpolDB4 update adds 26 new potentially phylogeographically-specific MTC genotype families. It provides a clearer picture of the current MTC genomes diversity as well as on the relationships between the genetic attributes investigated (spoligotypes) and the infra-species classification and evolutionary history of the species. Indeed, an independent Naïve-Bayes mixture-model analysis has validated main of the previous supervised SpolDB3 classification results, confirming the usefulness of both supervised and unsupervised models as an approach to understand MTC population structure. Updated results on the epidemiological status of spoligotypes, as well as genetic prevalence maps on six main lineages are also shown. Our results suggests the existence of fine geographical genetic clines within MTC populations, that could mirror the passed and present Homo sapiens sapiens demographical and mycobacterial co-evolutionary history whose structure could be further reconstructed and modelled, thereby providing a large-scale conceptual framework of the global TB Epidemiologic Network. CONCLUSION: Our results broaden the knowledge of the global phylogeography of the MTC complex. SpolDB4 should be a very useful tool to better define the identity of a given MTC clinical isolate, and to better analyze the links between its current spreading and previous evolutionary history. The building and mining of extended MTC polymorphic genetic databases is in progress.

Computational Biology↗
PubMed2006

Evidence for local transmission and reactivation of tuberculosis in the Toronto Somali community.

To further understand the molecular and clinical epidemiology of tuberculosis in the Toronto Somali community, molecular fingerprinting using IS6110 restriction fragment length polymorphism typing or spoligotyping was performed on M. tuberculosis isolates obtained from Somali-Canadians who developed active disease from 1997 to 2001. Molecular fingerprints were further compared with those obtained from Somalis residing in Denmark. 142 Somali TB patients were reported, for whom, 80 isolates were fingerprinted. 25% of isolates were clustered. Three clusters involving 2 patients each were identified out of the17 isolates that underwent spoligotyping. Of the 63 isolates typed by the IS6110 method, 6 clusters (4 of 2 patients and 2 of 3 patients) were identified. 57% of these isolates were found to be identical to Danish isolates. Our study suggests that a combination of reactivation and recent transmission are responsible for the high incidence rates of tuberculosis in this community. We recommend that ongoing surveillance and treatment programmes be directed towards this community.

Adult↗
PubMed2006

Routes of M. tuberculosis transmission among merchant seafarers.

For centuries, tuberculosis has been identified as a burden to seafarers. In this study, we assessed the magnitude of tuberculosis among merchant seafarers today. Furthermore, we identified the most likely routes of M. tuberculosis transmission by the use of DNA fingerprinting. A database containing all culture-positive tuberculosis cases in Denmark in 1992-2003 was combined with a register on all seafarers and their employment periods aboard Danish ships. All strains of M. tuberculosis were analysed using DNA-subtyping. 64 cases of culture positive tuberculosis among seafarers were identified. The risk of tuberculosis among males was 1.51 (1.10-2.01) compared with the general population. Two of the 64 cases were likely to be shipping-related, 5 were possibly shipping-related, and 10 were less likely to be shipping-related. The remaining 47 cases were very unlikely to be shipping related. Including the 2 first categories, the incidence was 0.09 cases per 1000 y at sea. The excess risk of tuberculosis among active and former Danish seafarers is most probably due to infections acquired in Denmark. Despite multi-cultural crews aboard, including many from high-incidence countries, our study indicates that only limited transmission of M. tuberculosis takes place among crew aboard modern ships or during shore leaves.

Adolescent↗
PubMed2006

Demographics of tuberculosis in an emerging EU region in southern Scandinavia.

To describe demographics of tuberculosis (TB) in the Øresund region, southern Scandinavia, a retrospective analysis of epidemiological data from TB registers and population databases, from 1995 to 2002, was performed. A total of 2678 TB cases were reported with an overall incidence of 6.3 per 100,000 person-y of observation. There were major differences in notification rates among immigrants depending on their country of origin and their residence in the Øresund region. In the Danish part, 37% of all cases among immigrants came from the Horn of Africa compared to 28% in the Swedish areas. Older age and residence in Denmark were independent risk factors for TB. Comparisons of TB rates within the group of immigrants from the Horn of Africa showed higher rates in the Danish areas compared to the Swedish areas. The discrepancies in notification rates could be explained by different socioeconomic circumstances in the 2 countries or by a greater immigration from highly endemic countries into Denmark during the study period; however, ongoing transmission in specific population groups at high risk of tuberculosis cannot be excluded. This highlights the need for continued and improved surveillance for TB, especially among newly arrived immigrants from highly endemic countries.

Adult↗
PubMed2004

Comparison of tuberculin skin test and new specific blood test in tuberculosis contacts.

The tuberculin skin test used to detect latent Mycobacterium tuberculosis infection has many drawbacks, and a new diagnostic test for latent tuberculosis (QuantiFERON-TB [QTF-TB]) has recently been introduced. This test measures the production of IFN-gamma in whole blood upon stimulation with purified protein derivative (PPD). The QTF-TB test addresses the operational problems with the tuberculin skin test, but, as the test is based on PPD, it still has a low specificity in populations vaccinated with the Bacille Calmette-Guérin (BCG) vaccine. We have modified the test to include the antigens ESAT-6 and CFP-10, which are not present in BCG vaccine strains or the vast majority of nontuberculous mycobacteria. This test was used to detect infection in contacts in a tuberculosis outbreak at a Danish high school. The majority of the contacts were BCG-unvaccinated, which allowed a direct comparison of the skin test and the novel blood test in individuals whose skin test was not confounded by vaccination. An excellent agreement between the two tests was found (94%, kappa value 0.866), and in contrast to the blood test based on PPD, the novel blood test was not influenced by the vaccination status of the subjects tested.

Adolescent↗
PubMed2004

Reactivation of tuberculosis during immunosuppressive treatment in a patient with a positive QuantiFERON-RD1 test.

A patient with polymyositis developed tuberculosis during immunosuppressive treatment. Tuberculin Skin Test and chest X-ray failed to demonstrate latent tuberculosis, whereas a blood sample that was tested with a modified QuantiFERON-TB-assay, using the recombinant ESAT-6 and CFP-10, was positive indicating that this patient was latently infected before immunosuppressive therapy. This case indicates the risk of progressing from latent to active tuberculosis given that the subject is RD1 responsive, and we believe that preventive anti-tuberculous treatment could have prevented this case of tuberculosis. We suggest that RD1 based tests are evaluated further in immunocompromised patients.

Antigens, Bacterial↗
PubMed2004

Definition of the Beijing/W lineage of Mycobacterium tuberculosis on the basis of genetic markers.

Mycobacterium tuberculosis Beijing genotype strains are highly prevalent in Asian countries and in the territory of the former Soviet Union. They are increasingly reported in other areas of the world and are frequently associated with tuberculosis outbreaks and drug resistance. Beijing genotype strains, including W strains, have been characterized by their highly similar multicopy IS6110 restriction fragment length polymorphism (RFLP) patterns, deletion of spacers 1 to 34 in the direct repeat region (Beijing spoligotype), and insertion of IS6110 in the genomic dnaA-dnaN locus. In this study the suitability and comparability of these three genetic markers to identify members of the Beijing lineage were evaluated. In a well-characterized collection of 1,020 M. tuberculosis isolates representative of the IS6110 RFLP genotypes found in The Netherlands, strains of two clades had spoligotypes characteristic of the Beijing lineage. A set of 19 Beijing reference RFLP patterns was selected to retrieve all Beijing strains from the Dutch database. These reference patterns gave a sensitivity of 98.1% and a specificity of 99.7% for identifying Beijing strains (defined by spoligotyping) in an international database of 1,084 strains. The usefulness of the reference patterns was also assessed with large DNA fingerprint databases in two other European countries and for identification strains from the W lineage found in the United States. A standardized definition for the identification of M. tuberculosis strains belonging to the Beijing/W lineage, as described in this work, will facilitate further studies on the spread and characterization of this widespread genotype family of M. tuberculosis strains.

China↗
PubMed2003

Stability of DNA patterns and evidence of Mycobacterium tuberculosis reactivation occurring decades after the initial infection.

Two hundred three freeze-dried strains of Mycobacterium tuberculosis collected during the 1960s were compared with 4102 strains collected during the 1990s, and 14 DNA patterns identified among the "historical strains" were 100% identical to patterns identified among the "recent strains." They were isolated from 41 and 40 patients who had tuberculosis during the 1960s and 1990s, respectively. The patients' mean age differed by >30 years, a finding strongly suggesting that the patients from the 1990s experienced reactivation of M. tuberculosis infection acquired during the 1960s. The half-life of IS6110 DNA patterns during latency was estimated to be 36 years (95% confidence interval, 25-54 years). Thus, this comparison of historical and recent strains yields molecular epidemiologic evidence of M. tuberculosis reactivation spanning decades and suggests that the rate of change of DNA patterns during latency is much longer than that during active disease. This has important implications for the interpretation of clustering, especially for the extent of recent transmission.

Adult↗
PubMed2003

Mannose-binding lectin polymorphisms in clinical tuberculosis.

Mannose-binding lectin (MBL) mediates protection against infections by using the complement system, but certain microorganisms may increase infectivity by exploiting this host defense system. Thus, it has been speculated whether genetically determined low MBL levels may confer partial protection against certain intracellular microorganisms, such as Mycobacterium tuberculosis. We investigated MBL alleles in 109 culture-positive human immunodeficiency virus-uninfected patients with tuberculosis living in Denmark and 250 white control subjects. Patients and control subjects were divided into 3 different groups defined by undetectable, low, and high serum MBL concentrations, which correlates to deficient, low, and high expressing MBL genotypes. A significantly decreased frequency of patients with the low-expressing MBL genotype was observed in white patients compared to control subjects. The same tendency also was observed in patients of other ethnic origin. It may be hypothesized that heterozygosity for MBL variant alleles, which encodes low serum MBL levels, is associated with protection against clinical tuberculosis.

Adult↗
PubMed2003

[Tuberculosis and molecular biology].

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB) hunting millions worldwide, is a challenge to work with in the laboratory. Modern molecular biology has provided extremely useful tools which have changed conventional diagnostic procedures in the TB laboratories. Research in molecular epidemiology is currently expanding our knowledge of the natural history of TB. Access to the genome sequence has opened new avenues for research in drug development and new vaccines. However, we are still awaiting the impact of these efforts in the resource-poor TB endemic countries.

Genetic Techniques↗
PubMed2003

Mycobacterium tuberculosis Beijing genotype.

Molecular epidemiologic studies of strains of Mycobacterium tuberculosis are currently conducted worldwide. The genetically distinct Beijing family of strains has been associated with large outbreaks of tuberculosis, increased virulence, and multidrug resistance. However, in this first population-based search for Beijing strains in the Danish DNA fingerprint database, analysis of 97% of all culture-positive tuberculosis patients in 1992 to 2001 showed that 2.5% of 3,844 patients, 1.0% of Danish-born patients, and 3.6% of immigrants (from 85 countries) had Beijing strains. No Beijing strains were found among 201 strains from Danish-born patients sampled in the 1960s, and no evidence of an increase in Beijing strains was found over time. The true prevalence of Beijing strains worldwide is unknown because only a fraction of global strains have been analyzed.

Adult↗
PubMed2002

Molecular evidence of endogenous reactivation of Mycobacterium tuberculosis after 33 years of latent infection.

Since Robert Koch described the cause of tuberculosis in 1882, the natural history of the disease after primary infection has been subject to debate. Only approximately 10% of infected individuals develop active disease, which may appear years to decades after infection. Late onset has been attributed to the endogenous reactivation of dormant bacteria. However, this has not been documented by molecular means for latencies of more than a few years. In Denmark, we have recently recultured 205 freeze-dried Mycobacterium tuberculosis strains obtained from 1961 through 1967. These "historical" strains are analyzed by DNA restriction fragment-length polymorphism testing, and their DNA patterns are compared with those of 4008 recently obtained clinical specimens. This has, surprisingly, yielded molecular evidence of M. tuberculosis reactivation after 33 years of latent infection. A father and son who developed tuberculosis in 1961 and in 1994, respectively, were the only patients infected with strains that share an identical DNA pattern.

Adult↗
PubMed2002

Bacillarity at autopsy in pulmonary tuberculosis. Mycobacterium tuberculosis is often disseminated.

The aim of this investigation was to quantify dissemination of Mycobacterium tuberculosis infection in patients with pulmonary tuberculosis and to show the pattern of eradication during treatment. The study is based on 98 out of the 113 patients with pulmonary tuberculosis who died during their admission to hospital in the Municipality of Copenhagen from 1963 to 1971. These patients had cultures for M. tuberculosis performed from different organs at autopsy: 78% treated <=100 days had dissemination of bacteria, cultured with decreasing frequency in the lungs, spleen, liver, and kidneys, respectively. In comparison, 23% treated >100 days had dissemination of bacteria, among which 50% occurred in patients with records of poor treatment compliance, 14% in patients with good treatment compliance. 81% of all patients had at least one chest x-ray judged to be without a miliary pattern. This study emphasizes that M. tuberculosis is often disseminated to organs other than the lungs in severe pulmonary tuberculosis. Eradication of bacteria in these organs can take several months. This observation adds to our understanding of the natural history of tuberculosis: M. tuberculosis is a resilient organism that can adapt to a wide variety of environmental conditions.

Adult↗
PubMed2002

Persistent high incidence of tuberculosis in immigrants in a low-incidence country.

Immigration from areas of high incidence is thought to have fueled the resurgence of tuberculosis (TB) in areas of low incidence. To reduce the risk of disease in low-incidence areas, the main countermeasure has been the screening of immigrants on arrival. This measure is based on the assumption of a prompt decline in the incidence of TB in immigrants during their first few years of residence in a country with low overall incidence. We have documented that this assumption is not true for 619 Somali immigrants reported in Denmark as having TB. The annual incidence of TB declined only gradually during the first 7 years of residence, from an initial 2,000 per 100,000 to 700 per 100,000. The decline was described by an exponential function with a half-time of 5.7 (95% confidence interval 4.0 to 9.7) years. This finding seriously challenges the adequacy of the customary practice of screening solely on arrival.

Denmark↗