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作者将伤寒杆菌Ty_2株为母株，采用克隆法使其缺失phoP／phoQ毒力调节基因，得到新的减毒株Ty800，制成口服伤寒减毒活菌苗。
The typhimurium Ty_2 strain as the parent strain, the cloning method to make it lacking phoP / phoQ virulence regulatory genes, get a new attenuated strain Ty800, made of oral attenuated live vaccine.