Location: Infectious Bacterial Diseases ResearchTitle: How does a Mycobacterium change its spots? Applying molecular tools to track diverse strains of Mycobacterium avium subspecies paratuberculosis Author
Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2013
Publication Date: 8/12/2013
Publication URL: http://handle.nal.usda.gov/10113/57404
Citation: Bannantine, J.P., Li, L., Sreevatsan, S., Kapur, V. 2013. How does a Mycobacterium change its spots? Applying molecular tools to track diverse strains of Mycobacterium avium subspecies paratuberculosis. Letters in Applied Microbiology. 57(3):165-173. Interpretive Summary: Johne’s disease in livestock such as dairy cattle and sheep is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). A major knowledge gap in Johne’s disease research involves the movement of this bacterium on the farm, but until recently, there was no way to track strains of MAP. With the genome sequences of MAP and molecular tools to distinguish strains, researchers can now ask the questions about if herd infections are polyclonal (contain multiple strains) or if a single strain predominates on the farm. Also, we can determine which strains are the most successful (virulent). Using the technique called single sequence repeat analysis, researchers have found that polyclonal infections occur in dairy cattle herds in the US. Furthermore, in Germany the single sequence repeat strain that predominates is designated 7_4. These represent solid beginnings in the molecular epidemiology of MAP. This review article is of primary interest to veterinarians, stakeholders and other researchers in the field.
Technical Abstract: Defining genetic diversity in the wake of the release of several Mycobacterium avium subsp. paratuberculosis (MAP) genome sequences has become a major emphasis in the molecular biology and epidemiology of Johne’s disease research. These data can now be used to define the extent of strain diversity on the farm. However, in order to perform these important tasks, researchers must have a way to distinguish the many MAP isolates/strains that are present in the environment or host to enable tracking over time. Recent studies have described genetic diversity of the Mycobacterium avium complex (MAC), of which MAP is a member, through pulsed-field gel electrophoresis, single sequence repeats, variable number tandem repeats, genome rearrangements, single nucleotide polymorphisms, and genomic comparisons to identify insertions and deletions. Combinations of these methods can now provide discrimination sufficient for dependable strain tracking. These molecular epidemiology techniques are being applied to understanding transmission of Johne’s disease within dairy cattle herds as well as identify which strains predominate in wildlife.