[Cloning and expression of Shiga-toxin gene from Shigella dysenteriae type I].

The chromosomal DNA of S. dysenteriae type I W30864 was isolated and digested by EcoRI. The 3-7 kb DNA fragments were recovered and ligated with vector pUC-19. After transformation, the recombinants were screened by SLT gene probe. The positive clones were obtained. The cloned EcoRI fragment containing both ST-A and ST-B subunit gene was about 4.5 kb. The cloned ST strain was also detected by Hela-S3 cell for cytotoxicity, and detected by rabbit ileal loop test for enterotoxicity. Besides, the cloned strain showed the neurotoxic activity when experimented with mouse. The production of shiga toxin in the cloned strain was 16 times of that of its parent strain S. dysenteriae W30864. The production differences between ST producing stains and SLT producing strain was also tested in our experiment.