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远在1901年,Nocard 从牛乳中分离到一株牛型结核分枝杆菌。后来 Calmette 和 Gueriu把它接种在胆汁马铃薯培养基上孵育,每隔二、三星期传代一次,至15代时,该菌株已不能使豚鼠得病——静脉注射100毫克,动物不死。传至第33代时,不仅小牛不发病,反使小牛对有毒结核菌产生了抵抗力。1907年卡介二氏发表了研究论文,报道该菌株毒力减低。1920年,经过235代培育后,证明了该菌株对马、牛、羊、猴、家兔及豚鼠等完全失去了致病性,
As far back as 1901, Nocard isolated a bovine Mycobacterium tuberculosis from milk. Later, Calmette and Gueriu inoculated it in bile potato medium and inoculated every two or three weeks. By the 15th generation, the strain was unable to make guinea pigs sick—intravenous injection of 100 mg did not cause death. When it was passed to the 33rd generation, not only did the calf not develop disease, but it also caused the calf to become resistant to TB. In 1907, Kasei Ershi published a research paper that reported that the virulence of the strain was reduced. In 1920, after 235 generations of breeding, it proved that the strain completely lost pathogenicity to horses, cattle, sheep, monkeys, rabbits and guinea pigs.