Identification of rickettsial isolates at the species level using multi-spacer typing

Background: In order to estimate whether multi- spacer typing ( MST), based on the sequencing of variable intergenic spacers, could serve for the identification of Rickettsia at the species level, we applied it to 108 rickettsial isolates or arthropod amplicons that include representatives of 23 valid Rickettsia species. Results: MST combining the dksA- xerC, mppA- purC, and rpmE- tRNA(fMet) spacer sequences identified 61 genotypes, allowing the differentiation of each species by at least one distinct genotype. In addition, MST was discriminatory at the strain level in six species for which several isolates or arthropod amplicons were available. Conclusion: MST proved to be a reproducible and high- resolution genotyping method allowing clear identification of rickettsial isolates at the species level and further additional differentiation of strains within some species.