Phylogenetic position of Rickettsia tsutsugamushi and the relationship among its antigenic variants by analyses of 16S rRNA gene sequences

Abstract

The 16S rRNA gene sequences of Rickettsia tsutsugamushi and Rickettsia sibirica were determined by PCR and DNA sequencing. Phylogenetic analysis revealed that R. sibirica is positioned in a cluster of the genus Rickettsia with a similarity value of 98.1-99.6%, whereas R. tsutsugamushi is located apart from the cluster with a similarity value of 90.2-90.6%. This evidence suggests that R. tsutsugamushi should be excluded taxonomically from the genus Rickettsia. The phylogenetic classification of six antigenic variants in R. tsutsugamushi moderately reflected their antigenic relationship known in closely and distantly related strains.

Phylogenetic Analysis of the 56 kDa Protein Genes of Orientia tsutsugamushi in Southwest Area of Korea

“…Because the 16s rRNA genes of the Gilliam, Karp, Kato, and Kuroki strains are ≥ 98.4% homologous, 29 this gene is useful for differentiating between Orientia and other genera/species, but not between O. tsutsugamushi strains. It has been reported that the 56-kDa protein gene is more useful for differentiating between O. tsutsugamushi strains than the 16s rRNA gene.…”

Isolation and Characterization of Orientia tsutsugamushi from Rodents Captured following a Scrub Typhus Outbreak at a Military Training Base, Bothong District, Chonburi Province, Central Thailand

“…Many previous studies have also shown that O. tsutsugamushi is closely related to but separate from Rickettsia spp. 2 The phylogenetic trees generated using the 16s rRNA gene did not show good resolution of O. tsutsugamushi phylogeny for characterizing evolutionary relationships between different O. tsutsugamushi strains or types caused by the low mutation rate of the 16s rRNA gene, therefore, the DNA variation within the gene could not resolve and characterize O. tsutsugamushi isolates variation. 41 However, the hyper variable region of the 56-kDa TSA gene of O. tsutsugamushi evolves faster and carries a higher mutation rate and therefore was chosen and used for resolving and characterizing evolutionary relationships of each isolate.…”

“…[1][2][3] Orientia tsutsugamushi is a member of the family Rickettsiaseae in the Proteobacteria α-subdivision based on 16s ribosomal RNA (rRNA) gene homology classification. 2,4 The bacterium size is ~0.5 μm wide and 1.2-3.0 μm long.…”

“…[1][2][3] Orientia tsutsugamushi is a member of the family Rickettsiaseae in the Proteobacteria α-subdivision based on 16s ribosomal RNA (rRNA) gene homology classification. 2,4 The bacterium size is ~0.5 μm wide and 1.2-3.0 μm long. 2,5,6 The pathogen is transmitted to humans by the bite of infected larval stage trombiculid mites, Leptotrombidium spp., commonly called chiggers.…”

“…2,4 The bacterium size is ~0.5 μm wide and 1.2-3.0 μm long. 2,5,6 The pathogen is transmitted to humans by the bite of infected larval stage trombiculid mites, Leptotrombidium spp., commonly called chiggers. 3,6,7 This mite-borne disease distributes across the Asia-Pacific region and causes substantial morbidity in an area stretching from Pakistan 8 in the west and Australia, 9,10 Japan, 11 Korea, 12,13 and Thailand, 14,15 in the east.…”