RESUMO
We have identified a clonal complex of Mycobacterium bovis isolated at high frequency from cattle in Uganda, Burundi, Tanzania, and Ethiopia. We have named this related group of M. bovis strains the African 2 (Af2) clonal complex of M. bovis. Af2 strains are defined by a specific chromosomal deletion (RDAf2) and can be identified by the absence of spacers 3 to 7 in their spoligotype patterns. Deletion analysis of M. bovis isolates from Algeria, Mali, Chad, Nigeria, Cameroon, South Africa, and Mozambique did not identify any strains of the Af2 clonal complex, suggesting that this clonal complex of M. bovis is localized in East Africa. The specific spoligotype pattern of the Af2 clonal complex was rarely identified among isolates from outside Africa, and the few isolates that were found and tested were intact at the RDAf2 locus. We conclude that the Af2 clonal complex is localized to cattle in East Africa. We found that strains of the Af2 clonal complex of M. bovis have, in general, four or more copies of the insertion sequence IS6110, in contrast to the majority of M. bovis strains isolated from cattle, which are thought to carry only one or a few copies.
Assuntos
Mycobacterium bovis/classificação , Mycobacterium bovis/isolamento & purificação , Tuberculose Bovina/epidemiologia , Tuberculose Bovina/microbiologia , África Oriental/epidemiologia , Animais , Técnicas de Tipagem Bacteriana , Bovinos , Análise por Conglomerados , Impressões Digitais de DNA , Elementos de DNA Transponíveis , DNA Bacteriano/química , DNA Bacteriano/genética , Dosagem de Genes , Genótipo , Dados de Sequência Molecular , Mycobacterium bovis/genética , Análise de Sequência de DNA , Deleção de SequênciaRESUMO
To further unravel the mechanisms responsible for attenuation of the tuberculosis vaccine Mycobacterium bovis BCG, comparative genomics was used to identify single nucleotide polymorphisms (SNPs) that differed between sequenced strains of Mycobacterium bovis and M. bovis BCG. SNPs were assayed in M. bovis isolates from France and the United Kingdom and from different BCG vaccines in order to identify those that arose during the attenuation process which gave rise to BCG. Informative data sets were obtained for 658 SNPs from 21 virulent M. bovis strains and 13 BCG strains; these SNPs showed phylogenetic clustering that was consistent with the geographical origin of the strains and previous schemes for BCG genealogies. The data revealed a closer relationship between BCG Tice and BCG Pasteur than was previously appreciated, while we were able to position BCG Beijing within a grouping of BCG Denmark-derived strains. Only 186 SNPs were identified between virulent M. bovis strains and all BCG strains, with 115 nonsynonymous SNPs affecting important functions such as global regulators, transcriptional factors, and central metabolism, which might impact on virulence. We therefore refine previous genealogies of BCG vaccines and define a minimal set of SNPs between virulent M. bovis strains and the attenuated BCG strain that will underpin future functional analyses.