恙蟲東方體

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恙蟲東方體
恙蟲東方體(Orientia tsutsugamushi)
恙蟲東方體(Orientia tsutsugamushi
科學分類
界: 細菌域 Bacteria
門: 變形菌門 Proteobacteria
綱: α-變形菌綱 Alpha Proteobacteria
目: 立克次體目 Rickettsiales
科: 立克次體科英语Rickettsiaceae Rickettsiaceae
屬: 東方體屬英语Orientia Orientia
種: 恙蟲東方體 O. tsutsugamushi
二名法
Orientia tsutsugamushi
(Hayashi 1920) Tamura et al. 1995

恙蟲東方體Orientia tsutsugamushi)是恙蟲病的病原體。其種小名「tsutsugamushi」源自於日语つつがむし」,為日本漢字「恙虫」兩字的發音[1]。恙蟲東方體的自然病媒及傳染窩為鉤恙蟎屬類的恙蟎[2][3]

恙蟲東方體為胞內病原體,需寄生於真核細胞內才能繁殖。其外膜結構類似革兰氏阴性菌,但並不容易以革蘭氏染色染色,必須採用Gimenez stain英语Gimenez stain。恙蟲東方體具有多種血清型,主要血清型包含 Karp(占總感染病例的半數)[3],另外還有Gilliam(25%)[3]、Kato(<10%)[3],以及Kawasaki等[4]。恙蟲東方體的血清型變化相當多樣[5][6][7] ,如馬來西亞同時就有八種血清型通報[8]。恙蟲病棘手的部分在於感染某一血清型之後,不代表對於其他血清型會具有免疫力。另外恙蟲東方體也可能在同一個體重複感染。

微生物學[编辑]

恙蟲東方體一開始被歸類於立克次體[1],但後來被重新分類於東方體屬英语Orienta,恙蟲東方體為該屬的唯一物種[9]

本種長約 1.2 至 3.0 µm,寬約 0.5 µm ,屬於絕對胞內寄生細菌。由於該物種毒力高,需於第三級以上防護實驗室才能操作[10]

抗生素療法[编辑]

恙蟲東方體在體外對於多西环素利福平,及阿奇霉素等抗生素敏感。但對β-内酰胺類藥物(如青黴素)則有抗藥性,因為本物種缺乏肽聚糖[11]。另外氨基糖苷类抗生素(如庆大霉素)在人體中也無效,因為該物種在活體內會寄生於細胞內,但此類抗生素無法穿越細胞膜。

疫苗[编辑]

目前恙蟲東方體尚無有效的疫苗,因為該物種具有許多血清型,且即使感染了一種血清型,也無法確保人體能對於另一種血清型產生免疫力。

參考文獻[编辑]

  1. ^ 1.0 1.1 Watt G, Parola P. Scrub typhus and tropical rickettsioses. Curr Opin Infect Dis. October 2003, 16 (5): 429–36. PMID 14501995. doi:10.1097/00001432-200310000-00009. 
  2. ^ Traub R, Wisseman CL Jr. The ecology of chigger-borne rickettsiosis (scrub typhus). J Med Entomol. 1974, 11 (3): 237–303. PMID 4212400. doi:10.1093/jmedent/11.3.237. 
  3. ^ 3.0 3.1 3.2 3.3 Kelly DJ, Fuerst PA, Ching W-M, Richards AL. Scrub typhus: The geographic distribution of phenotypic and genotypic variants of Orientia tsutsugamushi. Clin Infect Dis. 2009, 48 (s3): S203–30. PMID 19220144. doi:10.1086/596576. 
  4. ^ Yamamoto S, Kawabata N, Tamura A, 等. Immunological properties of Rickettsia tsutsugamushi, Kawasaki strain, isolated from a patient in Kyushu. Microbiol Immunol. 1986, 30 (7): 611–20. PMID 3095612. doi:10.1111/j.1348-0421.1986.tb02988.x. 
  5. ^ Kang JS, Chang WH. Antigenic relationship among the eight prototype and new serotype strains of Orientia tsutsugamushi revealed by monoclonal antibodies. Microbiol Immunol. 1999, 43 (3): 229–34. PMID 10338191. doi:10.1111/j.1348-0421.1999.tb02397.x. 
  6. ^ Bakshi D, Singhal P, Mahajan SK, Subramaniam P, Tuteja U, Batra HV. Development of a real-time PCR assay for the diagnosis of scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi. Acta Trop. 2007, 104 (1): 63–71. PMID 17870041. doi:10.1016/j.actatropica.2007.07.013. 
  7. ^ Parola P, Blacksell SD, Phetsouvanh R, 等. Genotyping of Orientia tsutsugamushi from Humans with Scrub Typhus, Laos. Emerg Infect Dis. 2008, 14 (9): 1483–1485. PMC 2603112. PMID 18760027. doi:10.3201/eid1409.071259. 
  8. ^ Shirai A, Tanskul PL, Andre, RG; 等. Rickettsia tsutsugamushi strains found in chiggers collected in Thailand. Southeast Asian J Trop Med Public Health. 1981, 12 (1): 1–6. PMID 6789455. 
  9. ^ Tamura A, Ohashi N, Urakami H, Miyamura S. Classification of Rickettsia tsutsugamushi in a new genus, Orientia gen. nov., as Orientia tsutsugamushi comb. nov. Int J Syst Bacteriol. 1995, 45 (3): 589–591. PMID 8590688. doi:10.1099/00207713-45-3-589. 
  10. ^ Centers for Disease Control and Prevention. Section VII-E: Rickettsial Agents. Biosafety in Microbiological and Biomedical Laboratories (BMBL) 4th. Washington DC: U.S. Government Printing Office. 1999: 149–53 [13 Mar 2009]. 
  11. ^ Amano K, Tamura A, Ohashi N, Urakami H, Kaya S, Fukushi K. Deficiency of peptidoglycan and lipopolysaccharide components in Rickettsia tsutsugamushi. Infect Immun. 1987, 55 (9): 2290–2. PMC 260693. PMID 3114150.