New Genotypes of Orientia tsutsugamushi Isolated from Humans in Eastern Taiwan

Abstract

Scrub typhus, an acute febrile illness, is caused by the obligate intracellular bacterium Orientia tsutsugamushi. In our study, O. tsutsugamushi was rapidly detected and typed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis of the 56-kDa type-specific antigen (TSA) gene. To investigate the genotypes of clinical variants of O. tsutsugamushi, we collected 3223 blood samples from eastern Taiwanese patients with suspected scrub typhus from 2002 to 2008. In total, 505 samples were found to be positive for scrub typhus infection by PCR, and bacteria were isolated from 282 of them. Four prototype genotype strains (Karp, Kato, Kawasaki and Gilliam) and eleven different Taiwanese genotype isolates (Taiwan-A, -B, -C, -D, -E, -G, -H, -J, -N, -O and -P) were identified by RPLF analysis. Taiwan-H, the major genotype in eastern Taiwan, exhibited prevalence and isolation rates of 47.3% (239/505) and 42.6% (120/282), respectively. We also assessed the genetic relatedness of the 56-kDa TSA gene among eight Taiwan-H isolates, thirteen other Taiwanese isolates and 104 DNA sequences deposited in the GenBank database using MEGA version 5.0 and PHYLIP version 3.66. We found that the Taiwan-H isolates formed into a new cluster, which was designated the Taiwan Gilliam-variant (TG-v) cluster to distinguish it from the Japanese Gilliam-variant (JG-v) cluster. According to Simplot analysis, TG-v is a new recombinant strain among Gilliam, Ikeda and Kato. Moreover, the Gilliam-Kawasaki cluster had the highest percentage of RFLP cases and was the most frequently isolated type in eastern Taiwan (50.1%, 253/505; 44.0%, 124/282). These findings shed light on the genetic evolution of O. tsutsugamushi into different strains and may be useful in vaccine development and epidemic disease control in the future.

Rapid Increase in Scrub Typhus Incidence in Mainland China, 2006–2014

“…7 Though largely sensitive to doxycycline, rifampicin, and azithromycin, O. tsutsugamushi is inherently resistant to treatment with β-lactam antibiotics and aminoglycosides, and an effective vaccine is currently not available. 8 Scrub typhus remains a serious public health problem in China. The first case of human infection with O. tsutsugamushi in China was identified in 1948 in Guangzhou, Guangdong Province.…”

Scrub Typhus Leading to Acute Encephalitis Syndrome, Assam, India

“…An optical density of > 0.5 was considered positive ( 5 ). We extracted DNA from the blood samples by using the QIAamp DNA blood mini kit (QIAGEN, Hilden, Germany) and performed nested PCR for amplification of a 56-kDa gene of Orientia, targeting a 483-bp fragment ( 6 ). We compared the sequences obtained with reference strains of Orientia .…”

Occurrence of Orientia Tsutsugamushi Genotypes in Areas of Union Territory of Puducherry and Tamil Nadu State, India

“…Two new genotypes have been reported from Himalayan region of India in an earlier study [31,32]. Yang et al reported 4 prototype/genotype strains (Karp, Kato, Kawasaki and Gilliam) and eleven different Taiwanese genotypes (Taiwan-A, B, C, D, E, G, H, J, N, O and P) based on RFLP analysis of the 56-kDa type-specific antigen (TSA) gene [33]. Taiwan-H was the major genotype in eastern Taiwan and it was designated as the Taiwan Gilliam-variant (TG-v) cluster.…”