How does a Mycobacterium change its spots? Applying molecular tools to track diverse strains of Mycobacterium avium subspecies paratuberculosis

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, 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 genomewide 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 understand transmission of Johne's disease within dairy cattle herds as well as identify which strains predominate in wildlife.

Typing of Mycobacterium avium Subspecies paratuberculosis Isolates from Newfoundland Using Fragment Analysis

“…Therefore, Map with these unique SSR-types could be present in Atlantic Canada, although SSR analysis has not been reported so far for a majority of herds from NB or NS for comparison. Another explanation for the distinctive genotypes could be that all SSR-types have not been reported yet as there are only a few published Map epidemiology studies using SSR analysis [ 25 ]. In addition, mononucleotide repeats up to 21 bp could be measured using fragment analysis, but all previous studies could only resolve SSR repeats up to 15 bp [ 5 , 14 , 18 , 23 , 26 ], which could influence their results.…”

“…In addition, mononucleotide repeats up to 21 bp could be measured using fragment analysis, but all previous studies could only resolve SSR repeats up to 15 bp [ 5 , 14 , 18 , 23 , 26 ], which could influence their results. This critical limitation of previously used technologies could underestimate Map SSR diversity despite the inclusion of a large number of isolates, as it is possible that not all loci were accurately resolved [ 5 , 19 , 23 , 25 ]. The only other published report which used fragment analysis for typing Map SSRs did not include the lengths of the repeats that could be analyzed [ 16 ], but it is conceivable that resolution comparable to what was observed in the current study would have been possible.…”

Development of a hierarchical typing approach for Mycobacterium avium subsp. paratuberculosis (MAP) and characterization of MAP field cultures from Central Germany

“…Basically, two major genetic lineages were described for MAP isolates, namely Cattle (C) type and Sheep (S) type (Biet et al 2012). Typing of the involved pathogen is a prerequisite for understanding the epidemiology of MAP infection and to trace back the sources of infection with an ultimate goal of designing more efficient control programmes (Bannantine et al 2013). It is also an important element for basic microbiological research investigating essential bacterial traits such as pathogenicity, virulence and antibiotic resistance (Li et al 2009).…”

“…Researchers have developed and applied a variety of MAP genotyping methods (Bannantine et al 2013). Especially in the last decade, mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR) were among the most commonly used markers for MAP genotyping mainly due to its portability and reproducibility (Castellanos et al 2010;Oakey et al 2014;R onai et al 2015).…”

Genetic diversity of Mycobacterium avium subspecies paratuberculosis and the influence of strain type on infection and pathogenesis: a review

“…The existence of phenotypically distinct strains of Map has been known for more than eight decades but the genetic differentiation of Map strain types has been challenging and only recent technologies have proven sufficiently discriminative for strain comparisons, tracing the sources of infection and epidemiological studies. The history of Map typing and the techniques employed has been reviewed elsewhere and will not be covered in this review [ 9 , 10 ]. It is important to understand the differences that exist between Map strains and how they influence both development and transmission of disease.…”