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''Francisella tularensis'' is a pathogenic species of Gram-negative, rod-shaped coccobacillus, an aerobe bacterium. It is non-spore forming, non-motile and the causative agent of tularemia, the pneumonic form of which is often lethal without treatment. It is a fastidious, facultative intracellular bacterium which requires cysteine for growth. Due to its low infectious dose, ease of spread by aerosol, and high virulence, ''F. tularensis'' is classified as a Tier 1 Select Agent by the U.S. government, along with other potential agents of bioterrorism such as ''Yersinia pestis, Bacillus anthracis'' and Ebola virus. == Subspecies == This species was discovered in ground squirrels in Tulare County, California, in 1911; ''Bacterium tularense'' was soon isolated by George Walter McCoy of the US Plague Lab in San Francisco and reported in 1912.〔(A. Tärnvik1 and L. Berglund, ''Tularaemia''. Eur Respir J 2003; 21:361-373. )〕〔McCoy GW, Chapin CW. Bacterium tularense, the cause of a plaguelike disease of rodents. Public Health Bull 1912;53:17–23.〕〔(Jeanette Barry, ''Notable Contributions to Medical Research by Public Health Service Scientists''. National Institute of Health, Public Health Service Publication No. 752, 1960, p. 36. )〕 Four subspecies (biovars) of ''F. tularensis'' have been classified. # The subspecies ''F. t. tularensis'' (or type A) is found predominantly in North America, is the most virulent of the four known subspecies, and is associated with lethal pulmonary infections. This includes the primary type A laboratory strain, SCHUS4. # Subspecies ''F. t. holarctica'' (also known as biovar ''F. t. palearctica'' or type B) is found predominantly in Europe and Asia, but rarely leads to fatal disease. An attenuated live vaccine strain of subspecies ''F. t. holarctica'' has been described, though it is not yet fully licensed by the FDA as a vaccine. This subspecies lacks the citrulline ureidase activity and ability to produce acid from glucose of biovar ''F. t. palearctica''. # Subspecies ''F. t. novicida'' (previously classified as ''F. novicida'') was characterized as a relatively nonvirulent strain; only two tularemia cases in North America have been attributed to ''F. t. novicida'' and these were only in severely immunocompromised individuals. # Subspecies ''F. t. mediasiatica'', is found primarily in central Asia; little is currently known about this subspecies or its ability to infect humans. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Francisella tularensis」の詳細全文を読む スポンサード リンク
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