Detection of new genotypes of Orientia tsutsugamushi infecting humans in Thailand

Abstract

PCR screening of blood specimens taken from 195 patients with serologically confirmed scrub typhus in three Thai provinces detected the 56-kDa protein-encoding gene from Orientia tsutsugamushi in ten (5%) patients. Significant genetic diversity was found among the ten amplicons, with nine new genotypes identified that were different from those found previously in Thailand. Phylogenetically, the ten sequences obtained in the present study and sequences from 71 strains characterised previously were distributed into several clusters that included the Karp, Gilliam, Kuroki, Saitama, Kawasaki and Kato clusters. Two of the new genotypes found in the present study clearly belonged to the Karp cluster. However, the other new genotypes formed three different clusters, including one cluster that appeared to be distant from all previously known clusters, and which may therefore be representative of a previously undescribed serotype. Other genotypes formed two other clusters that may also be associated with undescribed serotypes.

Antigenic Drift of Orientia tsutsugamushi in South Korea as Identified by the Sequence Analysis of a 56-kDa Protein-Encoding Gene

“…In endemic regions with low eschar prevalence, the buffy coat would be an alternative source of O. tsutsugamushi genetic material, but this would only be successful during the early phase of infection or within 1 week of antibiotic therapy. 1,26,27 The PHA method is widely used in South Korea because of its availability. 28 The indirect fluorescent antibody assay (IFA) has greater diagnostic sensitivity than PHA, but the overall diagnostic performance is also unsatisfactory.…”

Intrinsic fluoroquinolone resistance in Orientia tsutsugamushi

“…After 2 h of inoculation, the inoculum was removed and replaced by new media containing 0.4 g/mL daunorubicin (BIOMOL, Lausen, Switzerland), which partially inhibits the growth of host cells [20]. After 2 days of incubation, cells were collected and stained by indirect immunofluorescence assay using pooled human sera from Thai patients [2] with scrub typhus at a dilution A c c e p t e d M a n u s c r i p t 7…”

“…The disease is a public health concern for a population of over a billion humans in a geographical triangle extending from northern Japan and far eastern Russia in the north, to northern Australia in the south and Pakistan and Afghanistan in the west [1][2][3]. The estimated incidence of the disease in endemic areas is one million cases/year.…”

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

“…The clusters of genotypes in the strain pedigree were grouped by a modification of the method described by Tamura and others 15 and Fournier and others. 21 …”