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Evaluation of the discriminatory power of variable number tandem repeat (VNTR) typing of Mycobacterium bovis strains
Hilty, Markus
The discriminatory power of variable number tandem repeat (VNTR) typing based on 16 known loci (12 MIRUs, 3 ETRs and VNTR 3232) was assessed for Mycobacterium bovis strains collected sequentially at the slaughterhouse of N’Djaména, Chad. Of 67 M. bovis strains analyzed, 67% were clustered. In this study, VNTR typing was highly discriminative with an overall allelic diversity (hoa) of 0.922. We defined five loci (ETR A, B, C and MIRU 26, 27) as highly (h > 0.25), two loci (MIRU 4, and VNTR 3232) as moderately (0.11 < h < 0.25) and three loci (MIRU 16, 20, 31) as poorly (0.01 < h < 0.11) discriminative. Six loci (MIRU 2, 10, 23, 24, 39, and 40) showed no polymorphism at all. VNTR typing of the five highly discriminative loci (h = 0.917) proved to be most appropriate for first line typing of M. bovis strains of Chad and superior than spoligotyping (hsp = 0.789). In contrast to Mycobacterium tuberculosis strains, a consensus on VNTR loci needs to be found for M. bovis strains. The selection of a generally agreed set of VNTR loci for molecular discrimination of M. bovis in different geographical settings is discussed. Veterinary Microbiology 2005, Vol. 109, Issues 3-4, pp. 217-222 Available from: ScienceDirect
Mycobacterium bovis Isolates from Tuberculous Lesions in Chadian Zebu Carcasses
Diguimbaye, Colette
"This slaughterhouse study in Chad shows higher proportions of Mycobacterium bovis isolates among Mbororo than Arabe zebu cattle. Spoligotyping shows a homogenetic population structure for M. bovis and lack of spacer 30, as were found in neighboring Cameroon and Nigeria. This finding suggests transborder and ongoing transmission between cattle." Emerging Infectious Diseases 2006, Vol. 12, No. 5, pp. Available online from: Emerging Infectious Diseases Download PDF from: Emerging Infectious Diseases
Epidémiologie moléculaire des premiers isolements de mycobactéries chez l'animal au Tchad
Schelling, Esther
"The first laboratory to culture mycobacteria was established in Chad to confirm the presence of bovine tuberculosis and to describe the distribution of M. tuberculosis complex strains in livestock and humans. Specimens were collected on condemned animal carcasses due to tuberculosis. Spoligotyping and analysis of Variable Numbers Tandem Repeats (VNTRs) have been used on 67 M. bovis strains. The prevalence of tuberculosis-like lesions at the slaughterhouse was 7.3%. More M’bororo than Arab zebus were condemned (p = 0.04), M’bororo carcasses were more often entirely condemned in comparison to a partial condemnation (p ≤ 0.001) and M. bovis was more often isolated from Mbororo carcasses than from Arab zebu (p = 0.004). [...]" "Le premier laboratoire de culture des mycobactéries a été établi au Tchad pour confirmer la présence de la tuberculose bovine chez le bétail et pour évaluer la répartition des souches du complexe Mycobacterium tuberculosis. Les prélèvements ont été réalisés sur des carcasses d’animaux saisis pour cause de tuberculose. Le typage moléculaie par spoligotypie et le typage des VNTR (séquences répétées en nombre variable) ont été réalisés avec 67 souches M. bovis du Tchad. La prévalence de lésions tuberculeuses à l’abattoir était de 7,3%. Davantage de carcasse de zébus M’bororos ont été saisies par rapport aux zébus Arabes (p = 0,04); une saisie totale en comparaison à une saisie partielle a été plus souvent effectuée chez les Mbororos (p ≤ 0,001) et M. bovis a été plus fréquemment isolé chez les zébus Mbororos que chez les Arabes (p = 0,004). [...]" Épidémiologie et Santé Animale 2005, No. 48, pp. 81-91 Available for download from: L'Association pour l'Étude de l'Épidémiologie des Maladies Animales
Genetic Diversity in Mycobacterium ulcerans Isolates from Ghana Revealed by a Newly Identified Locus Containing a Variable Number of Tandem Repeats
Hilty, Markus
"The molecular typing methods used so far for Mycobacterium ulcerans isolates have not been able to identify genetic differences among isolates from Africa. This apparent lack of genetic diversity among M. ulcerans isolates is indicative of a clonal population structure. We analyzed the genetic diversity of 72 African isolates, including 57 strains from Ghana, by variable number of tandem repeat (VNTR) typing based on a newly identified polymorphic locus designated ST1 and the previously described locus MIRU 1. Three different genotypes were found in Ghana, demonstrating for the first time the genetic diversity of M. ulcerans in an African country. While the ST1/MIRU 1 allele combination BD/BAA seems to dominate in Africa, it was only rarely found in isolates from Ghana, where the combination BD/B was dominant and observed in all districts studied. A third variant genotype (C/BAA) was found only in the Amansie-West district. The results indicate that new genetic variants of M. ulcerans emerged and spread within Ghana and support the potential of VNTR-based typing for genotyping of M. ulcerans." Journal of Bacteriology 2006, Vol. 188, No. 4, p. 1462-1465 Available from: Journal of Bacteriology
Molecular epidemiology of mycobacteria
Hilty, Markus
PhD Thesis, University of Basel, Switzerland "One approach of molecular epidemiology of mycobacteria is the genotyping and comparison of DNA of infectious strains in order to monitor the transmission pathways of diseases. It is based on the assumption that patients infected with clustered strains are epidemiologically linked. Such results may help in understanding the modes of transmission and therefore in putting in place an adapted control strategy. [...] Therefore the overall aim of this study was to contribute to the development and refinement of innovative molecular typing tools in order to study Mycobacterium tuberculosis, bovis and ulcerans infections." Download
Bovine tuberculosis: an old disease but a new threat to Africa
Ayele, Wuhib Y.
"Bovine tuberculosis (TB) is a disease characterised by progressive development of specific granulomatous le-sions or tubercles in lung tissue, lymph nodes or other organs. Mycobacterium bovis is the causative agent of the disease. Bovine species, including bison and buffaloes, are susceptible to the disease, but nearly all warm-blooded animals can be affected. All species are not equally susceptible to the disease; some are spill-over (end) hosts and others maintenance hosts. In Africa, bovine TB primarily affects cattle; however, infection in other farm and domestic animals, such as sheep, goats, pigs, dogs and cats, is not uncommon. Wild ruminants and carnivores are also affected and are the natural reservoirs of the infectious agent in the wild. Man is also susceptible to the disease, the highest risk groups being individuals with concomitant HIV/AIDS infection. In Africa, human TB is widely known to be caused by M. tuberculosis; however, an unknown proportion of cases are due to M. bovis. This infection in humans is underreported as a result of the diagnostic limitations of many laboratories in distinguishing M. bovis from M. tuberculosis. None of the national reports submitted to the OIE and WHO by African member states mention the importance of M. bovis in human TB cases. Consumption of unpasteurised milk and poorly heat-treated meat and close contact with infected animals represent the main sources of infection for humans. This review attempts to examine the impact of bovine TB on the health of animals and humans." The International Journal of Tuberculosis and Lung Disease 2004, Vol. 8, No. 8, pp. 924-937(14) Freely available from: Ingentaconnect
Species identification of non-tuberculous mycobacteria from humans and cattle of Chad
Diguimbaye, Colette
"In Chad, during a study on tuberculosis in humans and cattle, 52 non-tuberculous mycobacteria (NTM) strains were isolated. By means of INNO-LiPA, PRA-hsp65 amplification and sequencing of 16S rDNA, NTM species of 25/52 isolates were identified. M. fortuitum complex (8) was the most frequent species, followed by M. nonchromogenicum (4) and M. avium complex (4). PRA method could identify M. fortuitum 3rd variant among isolates derived from cattle specimens. This finding could confirm the existence of farcy in the Chadian cattle population as M. fortuitum 3rd variant and putitative pathogen M. farcinogenes can't be distinguished by the methods used in this study. Half of the NTM isolates could not be specified and we considered them as contaminants from the environment." Schweizer Archiv für Tierheilkunde 2006, Vol. 148, No. 5, pp. 251-256 Available to purchase from: Verlag Hans Huber
Molecular Characterization and Drug Resistance Testing of Mycobacterium tuberculosis Isolates from Chad
Diguimbaye, Colette
"The molecular characterizations of the first 40 Mycobacterium tuberculosis isolates from Chad revealed a high proportion of isolates of the Cameroon family (33%), of which one isolate showed a monodrug resistance. In total, 9/33 (27%) isolates were resistant to isoniazid. The implications of these findings are discussed." Journal of Clinical Microbiology 2006, Vol. 44, No. 4, pp. 1575-1577 Available from: Journal of Clinical Microbiology