Nontoxic shigella flexneri with lipopolysaccharide synthesis deficiency and construction method thereof

Abstract

The invention discloses a nontoxic shigella flexneri with lipopolysaccharide synthesis deficiency and a construction method thereof. The invention provides a recombinant bacterium A, which is a recombinant bacterium obtained by removing large virulence plasmid in shigella flexneri 2a and O-antigen ligase coding gene in genome of the shigella flexneri 2a. Experiments show that according to the method of the invention, large virulence plasmid in shigella flexneri 2a 301 is firstly removed based on a plasmid exclusion principle, and a large virulence plasmid traceless deletion mutant 301 delta pCP is constructed, which is the nontoxic shigella flexneri; a target gene is substituted by a resistance gene by using homologous recombination technology based on the action of lambda bacteriophage Red recombinase; then the resistance gene is removed from a host bacterium under the action of transposase, and thus a waaI deletion strain of the nontoxic shigella flexneri is obtained.

Description

technical field [0001] The invention relates to the field of biotechnology, in particular to a strain of avirulent Shigella flexneri deficient in lipopolysaccharide synthesis and a construction method thereof. Background technique [0002] Shigella spp., commonly known as Shigella spp., is a highly contagious Gram-negative enteropathogenic bacterium, which mainly invades human colonic epithelial cells and finally locates in the large intestine, causing typical bacillary dysentery (fever , abdominal pain, tenesmus, fecal pus and blood), and the large virulence plasmid is the most important factor of its pathogenicity, containing about 32 genes related to virulence, mainly including mxi- spa gene, ipaBCD closely related to bacterial invasion of epithelial cells, and virulence genes such as ipgC. [0003] The infection dose of Shigella is extremely low (10-100 bacteria). In the annual statutory report of infectious disease epidemics announced by the Ministry of Health of my co...

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Problems solved by technology

At present, the main way to treat dysentery is antibiotics. Although there is no cross-immunity between different bacterial groups and serotypes, there is cross-drug resistance. In addition, the number of clinically isolated multi-drug-resistant strains continues to increase, and conventional antibiotic treatment has encountered huge challenges. ; Due to untimely treatment in the acute phase, improper use of drug-resistant strains, and incomplete treatment, etc., acute bacillary dysentery can turn into chronic bacillary dysentery, so the treatment of bacillary dysentery is increasingly challenged

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