• Clinical and Experimental Pediatrics
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• 제46권7호
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• pp.710-713
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• 2003

목 적 : 쯔쯔가무시병의 치료제로는 클로람페니콜 또는 독시싸이클린이 사용되고 있으나 소아에서는 재생불량성 빈혈의 위험성, 치아 착색 등의 합병증으로 연령에 따라 치료제의 선택에 어려움을 겪을 수 있다. 새로운 마크로라이드계 항생제의 하나인 록시쓰로마이신의 쯔쯔가무시병 환아에 대한 치료 효과을 알아보고자 하였다. 방 법 : 쯔쯔가무시병으로 치료받은 환아 39명을 대상으로 치료 약제에 따라 독시싸이클린으로 치료받은 16명(DC군), 클로람페니콜로 치료받은 14명(CM군)과 록시쓰로마이신으로 치료받은 9명(RM군)으로 나눈 후 각군의 평균 나이, 입원 전 발열일, 백혈구 수, 비정상 간효소치를 포함한 합병증 및 치료 시작 후 해열 시간을 후향적으로 비교하였다. 결 과 : 환아의 평균 연령은 $6.1{\pm}3.4$세이었고, 5세 이하의 환아가 20명(51%)을 차지하였으며, 남녀비에서 2.9 : 1를 보였다. 거의 모든 환아가 10, 11월에 발병하였으며 10월에 24명(62%), 11월에 14명(36%)이 발생하였다. 임상 증상으로 발열과 발진은 39명 모두에서 나타났으며, 가피(eschar)는 36명(92%)에서 발견되었다. 평균 나이는 DC군 $7.1{\pm}3.7$세, CM군 $5.8{\pm}3.1$세, RM군 $4.2{\pm}2.4$세로 DC군이 높았으나 통계학적으로 차이는 없었다. 입원 전 발열일, 백혈구수, CRP 및 비정상 간효소치를 보인 비율은 3군간의 통계학적 차이를 볼 수 없었다. 대부분의 환아는 24시간 안에 해열되었으며(35명, 89.7%), 24-48시간 사이에 해열된 환아는 DC군에서 2명, CM군에서 1명, RM군에서 2명이었으며 통계학적으로는 차이를 보이지 않았다. 결 론: 소아의 쯔쯔가무시 병의 치료에서 록시쓰로마이신이 기존의 독시싸이클린이나 클로람페니콜과 같은 효과를 보였으며, 두 약제에서 볼 수 있는 합병증이 없어 사용하기 더 안전할 것으로 사료된다.

• Parasites, Hosts and Diseases
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• 제61권3호
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• pp.272-281
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• 2023

Chigger mites are the vector of scrub typhus. This study estimates the infestation status and ecological characteristics of chiggers on the chestnut white-bellied rat Niviventer fulvescens in Southwest China between 2001 and 2019. Chiggers were identified under the microscope, and infestation indices were calculated. The Preston's log-normal model was used to fit the curve of species abundance distribution. A total of 6,557 chiggers were collected in 136 of 342 N. fulvescens rats, showing high overall infestation indices (prevalence=39.8%, mean abundance=19.2, mean intensity=48.2) and high species diversity (S=100, H'=3.0). Leptotrombidium cangjiangense, Neotrombicula japonica, and Ascoschoengastia sifanga were the three dominant chigger species (constituent ratio=42.9%; 2,736/6,384) and exhibited an aggregated distribution among different rat individuals. We identified 100 chigger species, with 3 of them (Leptotrombidium scutellare, Leptotrombidium wenense, and Leptotrombidium deliense) as the main vectors of scrub typhus in China and nine species as potential vectors of this disease. Disease vector occurrence on N. fulvescens may increase the risk of spreading scrub typhus from rats to humans. Chigger infestation on N. fulvescens varied significantly in different environments. The species abundance distribution showed a log-normal distribution pattern. The estimated number of chigger species on N. fulvescens was 126 species.

• 미생물학회지
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• 제41권3호
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• pp.232-235
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• 2005

Scrub typhus의 원인병원체인 Orientia tsutsugamushi에 감염된 인간 피부 미세혈관 내피세포(HMEC-1)에서 superoxide dismutase 유전자의 발현이 증가하였다. O. tsutsugamushi 접촉 후 5 시간 이내에 감염된 세포에서 세포내 peroxide 존재를 유세포 분석을 통하여 관찰할 수 있었다. 또한 감염된 세포는 세포 내 glutathione이 심하게 고갈됨을 관찰하였다. 이 결과들은 이 절대세포내 기생세균에 감염된 숙주세포가 산화-매개 손상 받음을 시사한다.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 2005년도 제57차 추계 학술대회 연제집
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• pp.481-481
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• 2005

• Journal of Microbiology
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• 제39권2호
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• pp.142-145
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• 2001

Changes in the Activities of several antioxidant enzymes in transformed human dermal microvascular endothelial Cells (HMEC-1) by infection with the obligate intracellular bacterium Orientia tsutsugamushi, the causative agent of scrub typhus, were investigated. The activities of glucose-6-phosphate dehydrogenase, catalase, and glutathione peroxidase were significantly decreased in HMEC-1 cells infected with Ο. tsutsugamushi. However, the level of superoxide dismutase increased slightly. Furthermore, Increased levels of intracellular peroxide was observed in HMEC-1 during infection. These results support the hypothesis that cells infected by this intracellular bacterium experience oxidant-mediated injury that may eventually contribute to cell death.

• 대한미생물학회지
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• 제35권2호
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• pp.159-169
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• 2000

Scrub typhus is caused by Orientia tsutsugamushi characterized by fever, headache, lymphadenopathy and eschar formation. Infiltration of inflammatory cells around blood vessels and within the affected organs isS known to be pathologic hallmark of the scrub typhus. Recently, expression of adhesion molecules on vascular endothelial cells was implicated as an important pathogenic mechanism in rickettsial disease. This study was performed to examine the expression of adhesion molecules and to investigate its role in the pathogenesis of O. tsutsugamushi infection. The expression of adhesion molecules on human umbilical vein endothelial cells (HUVEC) was measured by flow cytometry and indirect immunofluorescence. Expression of E-selectin, ICAM-1 and VCAM-1 was significantly increased 4 hours after the infection and persisted at least for 24 hours. Expression of those molecules was not induced by killed O. tsutsugamushi. Adhesion of polymorphonuclear cells and mononuclear cells to HUVEC was increased after the infection with O. tsutsugamushi. In conclusion, adhesion molecules are expressed on HUVEC during the infection of live O. tsutsugamushi and those molecules can contribute to the infiltration of inflammatory cells during the infection.

• IMMUNE NETWORK
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• 제23권6호
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• pp.47.1-47.16
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• 2023

Scrub typhus, a mite-borne infectious disease, is caused by Orientia tsutsugamushi. Despite many attempts to develop a protective strategy, an effective preventive vaccine has not been developed. The identification of appropriate Ags that cover diverse antigenic strains and provide long-lasting immunity is a fundamental challenge in the development of a scrub typhus vaccine. We investigated whether this limitation could be overcome by harnessing the nanoparticle-forming polysorbitol transporter (PST) for an O. tsutsugamushi vaccine strategy. Two target proteins, 56-kDa type-specific Ag (TSA56) and surface cell Ag A (ScaA) were used as vaccine candidates. PST formed stable nano-size complexes with TSA56 (TSA56-PST) and ScaA (ScaA-PST); neither exhibited cytotoxicity. The formation of Ag-specific IgG2a, IgG2b, and IgA in mice was enhanced by intranasal vaccination with TSA56-PST or ScaA-PST. The vaccines containing PST induced Ag-specific proliferation of CD8⁺ and CD4⁺ T cells. Furthermore, the vaccines containing PST improved the mouse survival against O. tsutsugamushi infection. Collectively, the present study indicated that PST could enhance both Ag-specific humoral immunity and T cell response, which are essential to effectively confer protective immunity against O. tsutsugamushi infection. These findings suggest that PST has potential for use in an intranasal vaccination strategy.

• Parasites, Hosts and Diseases
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• 제58권2호
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• pp.153-159
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• 2020

The chigger mite Leptotrombidium sialkotense is one of the 6 main vectors of scrub typhus in China. Before present study, L. sialkotense was found in some parts of Hunan province, China with a narrow geographical distribution. During field investigation 2016-2017, we found L. sialkotense in Jingha, southern Yunnan, China. Of 15 small mammal host species, L. sialkotense were collected from 6 species of the hosts. Rattus brunneusculus was a dominant host of L. sialkotense, from which 98.3% of the mites were collected. The chigger mite showed a relatively high infestation prevalence (P_M =11.7%) and mean abundance (MA=0.5) in comparison with the rest 5 host species. These results reveal a certain host specificity of L. sialkotense to a rat R. brunneusculus. The mite L. sialkotense showed an aggregated distribution on the host (P<0.05). A positive correlation observed between L. sialkotense and the body length of hosts. There was a positive interspecific association between L. sialkotense and 2 other dominant vectors, L. deliense and L. scutellare.

• Journal of Microbiology
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• 제40권2호
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• pp.151-155
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• 2002

A Superoxide Dismutase (SOD) gene from the obligate intracellular bacterium Orientia tsutsugamushi has been cloned by using the polymerase chain reaction with degenerate oligonucleotide primers corresponding to conserved regions of known SODs. Nucleotide sequencing revealed that the predicted amino acid sequence was significantly more homologous to known iron-containing SODs (FeSOD) than to manganese-containing SODs (MnSOD). Conserved regions in bacterial FeSOD could also be seen. Isolation of the oriential SOD gene may provide an opportunity to examine its role in the intracellular survival of this bacterium.

• Parasites, Hosts and Diseases
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• 제58권4호
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• pp.445-450
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• 2020

Trombiculid "chigger" mites (Acari) are ectoparasites that feed blood on rodents and another animals. A crosssectional survey was conducted in 7 ecosystems of southern Vietnam from 2015 to 2016. Chigger mites were identified with morphological characteristics and assayed by polymerase chain reaction for detection of rickettsiaceae. Overall chigger infestation among rodents was 23.38%. The chigger index among infested rodents was 19.37 and a mean abundance of 4.61. A total of 2,770 chigger mites were identified belonging to 6 species, 3 genera, and 1 family, and pooled into 141 pools (10-20 chiggers per pool). Two pools (1.4%) of the chiggers were positive for Orientia tsutsugamushi. Ricketsia spp. was not detected in any pools of chiggers. Further studies are needed including a larger number and diverse hosts, and environmental factors to assess scrub typhus.