Genetic diversity of Borrelia burgdorferi and detection of B. bissettii-like DNA in serum of north-coastal California residents

Abstract

In North America, Lyme borreliosis (LB) is a tick-borne disease caused by infection with the spirochete Borrelia burgdorferi. We studied the genetic diversity of LB spirochetes in north-coastal California residents. Spirochete DNA was detected in 23.7% (27/114) of the study subjects using a PCR protocol optimized for increased sensitivity in human sera. Californians were most commonly infected with B. burgdorferi ospC genotype A, a globally widespread spirochete associated with high virulence in LB patients. Sequence analysis of rrf-rrl and p66 loci in 11% (3/27) of the PCR-positive study subjects revealed evidence of infection with an organism closely related to B. bissettii. This spirochete, heretofore associated with LB only in Europe, is widely distributed among ticks and wildlife in North America. Further molecular testing of sera from residents in areas where LB is endemic is warranted to enhance our understanding of the geographic distribution and frequency of occurrence of B. bissettii-like infections.

Fig. 1.

Unrooted 50% majority rule consensus tree for B. burgdorferi sensu lato rrf-rrl alignment (204 bp) determined by Bayesian analysis using the nucleotide substitution model HKY + Γ (5,000,000 generations; burn-in, 0.5; sample frequency, 1,000; four chains). Values at nodes refer to Bayesian posterior probabilities (the proportion of sampled trees containing the taxon bipartition). The scale bar corresponds to branch length, expressed as the number of substitutions per site. Taxon names given to CHR serum specimens are in bold. GenBank accession numbers for sequences generated during this study also are in bold.

Fig. 2.

Unrooted 50% majority rule consensus tree for B. burgdorferi sensu lato p66 alignment (207 bp) determined by Bayesian analysis using a codon-based model of nucleotide substitution (1,000,000 generations; burn-in, 0.5; sample frequency, 1,000; four chains). Taxon names given to CHR serum specimens are in bold. GenBank accession numbers for sequences generated during this study also are in bold. Values at nodes and branch lengths are defined in the legend to Fig. 1.

Fig. 3.

Unrooted 50% majority rule consensus tree for concatenated alignments of B. burgdorferi sensu lato rrf-rrl and p66 loci (395 bp) determined by Bayesian analysis using partitioned nucleotide substitution models: HKY + Γ and codon based (1,000,000 generations; burn-in, 0.5; sample frequency, 1,000; four chains). Taxon names given to CHR serum specimens are in bold. Values at nodes and branch lengths are defined in the legend to Fig. 1.