Genetic diversity of Borrelia burgdorferi sensu stricto: Novel strains from Mexican wild rodents.

Abstract

Borrelia burgdorferi s.s. is a Gram-negative spirochaete, the aetiological agent of Lyme disease, the most common vector-borne disease in the Northern hemisphere. Reports on the presence of B.burgdorferi in central Mexico have been strongly criticized, since these were based only on unspecific serological methods. Furthermore, the worldwide genetic diversity of B.burgdorferi s.s. has not been evaluated. For this reason, the aim of the present study was to confirm the presence of B.burgdorferi in the central area of Mexico and to evaluate its relationship with regard to the global genetic diversity of B.burgdorferi s.s. To achieve this, fragments of the flagellin and the outer surface protein A genes were amplified from ear biopsies of the arboreal wild endemic mice Habromys schmidlyi. With these sequences, a concatenated Bayesian analysis was performed to confirm the identity of B.burgdorferi s.s. Afterwards, the global genetic diversity of this bacterial species was evaluated using our sequences and those available in GenBank. A prevalence of 10.4% (5/48) of H.schmidlyi infected with Borrelia sp. was detected, and the phylogenetic analyses confirmed the identity of B.burgdorferi s.s. Using both genes, the genetic diversity was low. However, genetic structuring analyses revealed that populations of western United States and those from Mexico formed slightly different genetic groups, separated from the populations of the rest of the world. Our study not only confirms the presence of this bacterium in central Mexico, but also shows the most southern record of this bacterium so far. It also highlights the importance of H.schmidlyi as a new potential host of this bacterial species. Our study also provides first genetic data on an incipient process of divergence in B.burgdorferi s.s. populations of eastern United States and central Mexico.