Phylogenesis of Relapsing Fever Borrelia spp.

Abstract

The phylogenetic relationships of 20 relapsing fever (RF) Borrelia spp. were estimated on the basis of the sequences of rrs genes. Complete sequences were aligned and compared with previously published sequences, and the similarity values were found to be 97.7 to 99.9%. Phylogenetic trees were constructed by using the three neighbor-joining, maximum-parsimony, and maximum-likelihood methods. The results of the comparative phylogenetic analysis divided the RF Borrelia spp. into three major clusters. One cluster included Borrelia crocidurae, Borrelia duttonii, Borrelia recurrentis, and Borrelia hispanica. Another cluster comprised tow main branches with Borrelia coriaceae, Borrelia lonestari, and Borrelia miyamotoi on one side and Borrelia parkeri, Borrelia turicatae, and Borrelia hermsii on the other side. Borrelia anserina constituted the third cluster. The phylogenetic position of Borrelia persica was more uncertain. These results suggested that the taxonomy of these spirochetes should be revised. To overcome the problems of culturing the spirochetes, RF Borrelia primers were defined. Following PCR amplification of the rrs gene, restriction length fragment polymorphism could be used to distinguish between RF Borrelia strains.

Typing African Relapsing Fever Spirochetes

“…duttonii and B . recurrentis ; this finding was also reported previously ( 12 ). Ras et al concluded that this small difference did not support these being single species but instead postulated that B .…”

“…recurrentis , and B. crocidurae ; however, a small number of nucleotides differentiated these clusters. Some Old World relapsing fever spirochetes show a high degree of similarity, both in using 16S RNA gene sequences ( 12 ) and in flagellin ( 20 , 24 ). Using the 16S RNA gene, we found that only 4 bases differed over the rr s gene between B .…”

“…recurrentis complex, however, would require the use of alternative targets, if they are indeed different species. This apparent paradox may reflect that these are clones derived from a common ancestral origin ( 12 ). This hypothesis is strengthened by the finding of a partial IGS sequence ( B .…”

“…Although conventional approaches, such as sequencing of 16SRNA gene, have provided useful information on population structure among the Borrelia spp., this gene only provides low discriminatory resolution among African relapsing fever spirochetes ( 2 , 12 ). Others have used the flagellin gene as a target for population structure ( 5 , 13 ); however, as with 16SRNA, these methods, although useful for interspecies comparisons, are of limited value for discrimination of African relapsing fever spirochetes and for intraspecies analysis.…”

Possibilities for Relapsing Fever Reemergence

“…Human infection with B. crocidurae appears to be more prevalent than previously described, however ( 14 ). This increase could be attributed to improved diagnostic capabilities and sample processing ( 15 ), but it is largely due to molecular techniques that can facilitate not only detection but also subsequent identification through sequencing the target gene ( 16 , 17 ). …”