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

AIMS: Development of a novel hierarchical MAP typing approach and characteristion of MAP field cultures in Central Germany. METHODS AND RESULTS: By combining single nucleotide polymorphisms (SNPs) and mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR), we developed a highly discriminating and phylogenetically accurate hierarchical MAP typing approach. Moreover, a novel stepwise workflow was employed to reduce the number of SNP reactions required making the typing approach more affordable. MAP field cultures (n=142) from dairy herds in Central Germany were classified as cattle type and showed a high level of heterogeneity. Intra-herd multiple genotypes were evident in (13-25%) of the investigated herds. CONCLUSIONS: The hierarchical MAP typing approach proved to be useful in fine discrimination between MAP cultures within limited geographical regions. This could potentially be used in unravelling MAP transmission chains in the respective regions. The observed heterogeneity in some herds is assumed to be due to either multiple introductions through inter-herd trade or intra-herd evolution over time. SIGNIFICANCE AND IMPACT OF THE STUDY: Future MAP epidemiological studies will benefit from the advantages of the novel hierarchical typing approach. The SNP number reduction approach employed here could be extrapolated for other analogous pathogens.