Trans-Atlantic exchanges have shaped the population structure of the Lyme disease agent Borrelia burgdorferi sensu stricto

Abstract

The origin and population structure of Borrelia burgdorferi sensu stricto (s.s.), the agent of Lyme disease, remain obscure. This tick-transmitted bacterial species occurs in both North America and Europe. We sequenced 17 European isolates (representing the most frequently found sequence types in Europe) and compared these with 17 North American strains. We show that trans-Atlantic exchanges have occurred in the evolutionary history of this species and that a European origin of B. burgdorferi s.s. is marginally more likely than a USA origin. The data further suggest that some European human patients may have acquired their infection in North America. We found three distinct genetically differentiated groups: i) the outgroup species Borrelia bissettii, ii) two divergent strains from Europe, and iii) a group composed of strains from both the USA and Europe. Phylogenetic analysis indicated that different genotypes were likely to have been introduced several times into the same area. Our results demonstrate that irrespective of whether B. burgdorferi s.s. originated in Europe or the USA, later trans-Atlantic exchange(s) have occurred and have shaped the population structure of this genospecies. This study clearly shows the utility of next generation sequencing to obtain a better understanding of the phylogeography of this bacterial species.

Nested coevolutionary networks shape the ecological relationships of ticks, hosts, and the Lyme disease bacteria of the Borrelia burgdorferi (s.l.) complex

“…The constructed network of pathogens , their vertebrate hosts and their vectors formed a structure of redundant interconnections. Some species of BBG linked a few otherwise isolated clusters, suggesting invasion events and further spread; these have been described previously [ 10 ]. However, undetermined BBG genospecies were included in the network in order to use data obtained before modern molecular techniques became available, and this could result in bias in terms of the structure of the clusters.…”

Primordial origin and diversification of plasmids in Lyme disease agent bacteria

“…Plasmids similar to the fused lp56 present in the New York isolate B31 were identified by Palmer et al [ 114 ] in two (Connecticut) isolates out of eleven New England B. burgdorferi isolates tested. In addition, lp56 plasmids that are essentially identical to B31 lp56 are present in the sequenced genomes of two B. burgdorferi type A isolates PAbe and PAli isolated from two German patients that likely were infected in North America [ 55 , 115 ]. The fact that these three plasmids are almost certainly all the result of a single past fusion event [ 20 , 30 ], suggests that reversal of this fusion is not rapid.…”

Rapid Gene Turnover as a Significant Source of Genetic Variation in a Recently Seeded Population of a Healthcare-Associated Pathogen

“…Over the last two decades genome sequencing has allowed us to better understand not only the microevolution but also the epidemiology of many bacterial pathogens. For instance, this tool has been used to study the phylogeography and population structure of several human and animal bacterial pathogens (Brynildsrud et al, 2014 ; Ezewudo et al, 2015 ; Joseph et al, 2015 ; Castillo-Ramirez et al, 2016 ). It has also been employed to study the impact of recombination on bacterial clones (Castillo-Ramirez et al, 2011 , 2012 ) and even to analyse the intra-host evolution of several human pathogens (Diaz Caballero et al, 2015 ; Azarian et al, 2016 ).…”