Orientia tsutsugamushi is the etiological agent of scrub typhus, a mite-borne, febrile illness that occurs in the Asia-Pacific region. We conducted strain characterization of O. tsutsugamushi isolates from chiggers obtained from rodents based the nucleotide sequence of the 56-kDa outer membrane protein gene. With the use of PCR, a total of 68 DNA sequences of 56-kDa antigen genes were amplified. Phylogenetic analysis revealed that there were at least six definable clusters among the 68 isolates: 37% Karp-related strains (25/68), 27% TA763 strains (18/68), 12% JG-related strains (8/68), 19% Kato-related strains (13/68), 4% divergent strains (3/68), and 1% representing a Gilliam prototype strain (1/68). Overall, the O. tsutsugamushi genotypes exhibited a high degree of diversity, similar to that seen in strains from the rest of the areas where scrub typhus is endemic. Orientia tsutsugamushi is an obligate intracellular, Gramnegative bacterium that causes scrub typhus, an acute febrile illness characterized by a typical primary lesion (eschar), lymphadenopathy, and nonspecific symptoms such as chills, headache, and malaise (10, 24). The disease is endemic in Asian countries, including Japan, South Korea, China, Thailand, and Taiwan (6, 13). An estimated 1 million cases occur annually (22). However, the precise incidence of this disease is unknown, as the available diagnostic facilities in most of the region of endemicity are limited (32). In nature, the bacterial agent is maintained within a life cycle involving wild mammals and a mite vector, primarily of the Leptotrombidium genus (14). Humans are accidentally infected by the bites of a larval mite, known as a chigger, during feeding (30).The 56-kDa type-specific antigen (TSA) gene encodes a dominant membrane protein, which accounts for 10% to 15% of the total protein of O. tsutsugamushi (17). The deduced size of the 56-kDa protein varies from 516 to 541 amino acids, according to gene sequences deposited in the GenBank (11). It is highly immunogenic, and the sera of most patients with scrub typhus are reactive. Serological analyses show that the antigenicity of the 56-kDa protein is diverse and includes variants such as the representative Karp-, Gilliam-, and Kato-type strains and other isolates (2,8,18). The immune responses to the 56-kDa protein provide protection against Scrub typhus, suggesting that it is a potential candidate for vaccine development (3,16,33). No commercially licensed vaccine for scrub typhus is currently available.In the present study, we cloned and sequenced the 56-kDa TSA gene of O. tsutsugamushi isolated from the chigger mite obtained from a rodent in order to understand the genetic types as well as the relationships with other known strains. Our results demonstrated that the genotypes of O. tsutsugamushi isolates appeared highly diverse and widely and geographically distributed in Taiwan. MATERIALS AND METHODSStudy site and arthropod collection. All the arthropods used in this study were collected from rodents captured by randomly settin...

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a b s t r a c tThis study investigates the microstretch continuum modeling of granular assemblies while accounting for both the dilatant and rotational degrees of freedom of a macroelement. By introducing the solid volume fraction and the gyration radius of a granular system, the balance equations of the microstretch continuum are transformed into a new formulation of evolution equations comprising six variables: the solid volume fraction, the gyration radius, the velocity field, the averaged angular velocity, the rate of gyration radius, and the internal energy. The bulk microinertia density, the averaged angular velocity, and the microgyration tensor at a macroscopic point are obtained in terms of discrete physical quantities. The bulk part and the rotational part of the microgyration tensor are proposed as the two indices to measure the local dilatancy and local rotation of granular assemblies. It is demonstrated in the numerical simulation that the two indices can be used to identify the shear band evolution in a granular system under a biaxial compression.