动物造模,药效评价,大肠杆菌 z-bio 2024-08-19 347

　　Normally, mice are not sensitive to wild-type EHEC O157: H7 infection. Adult mice of IQI, BALB/c, KM and other strains are not susceptible to O157. Vaccination with live EHEC O157 EDL933W (NalR) at a dose of 10 ^ 10 to the power of 10 did not cause significant infection symptoms in weaned mice. Therefore, in addition to bacterial infection, drug assistance should also be used to increase animal sensitivity in order to replicate some of the symptoms of human EHEC infection, which can be used for preliminary screening of anti-O157: H7 vaccines.

　　(1) Method: Oral inoculation of bacteria (this strain is resistant to nalidixic acid), fasting for 12 hours before gavage. Resume diet 12 hours after inoculation. At the same time as vaccination, intraperitoneal injection of mitomycin C (2.5mg/kg) was administered, and naphthonic acid (50 μ g/ml) was added to drinking water.

　　(2) Infection dose: 10 ^ 9 to 4 × 10 ^ 9 live bacteria per individual.

　　(3) Result: Infected mice developed symptoms and died within 3-4 days. This model can replicate the classic histopathological changes of O157: H7 infection, including bleeding and edema in the lamina propria, neutrophil infiltration in colon biopsy specimens, but the lesions are not severe, there is no A/E injury, and no diarrhea or colitis is caused. It should not be the direct cause of mouse death. EDL933W can cause damage to mouse renal parenchymal cells in the experiment; Liver cells exhibit severe granular degeneration and vesicular degeneration, with liver cell degeneration around the central vein of the liver lobule being more severe; The lesions in lung tissue are the most obvious, with highly tortuous and dilated capillaries in the alveolar walls, containing a large number of red blood cells. The alveolar cavity contains pink fluid and a small amount of red blood cells. Local lung tissue bleeding occurs, and some alveoli show compensatory emphysema changes. Typical E. coli granulomas can be seen around the bronchi, with a large number of epithelioid cells and inflammatory cells infiltrating. The possible reason is that there are more Stx receptors Gb3 in the lungs of mice.

　　Inject mitomycin C (2.5mg/kg) intraperitoneally while inoculating with bacteria, and add nalidixic acid to drinking water. The action of mitomycin C is similar to that of cyclophosphamide, which can cause a decrease in white blood cells and platelets. EHEC O157 is a lysogenic bacterium, and mitomycin C can increase the release of Stx2 bacteriophage, thereby increasing the production of Shiga toxin Stx, a characteristic virulence factor of EHEC. The function of naphthonic acid is to inhibit the normal gut microbiota, making EHEC O157 EDL933 W (NalR) the dominant microbiota in the intestine. If EHEC is transmitted orally or through the stomach, it is usually necessary to use streptomycin to eliminate the normal flora in the animal's intestine in advance, allowing streptomycin resistant strains of EHEC to colonize in the intestine. Mice infected with EHEC in this way showed renal tubular necrosis damage. In addition, mouse models have been used to study the oral and non oral EHEC infections of Stx. Intraperitoneal injection of Stx1 or Stx2 can cause colonic mucosal necrosis and bleeding, lymphatic necrosis in various tissues, and nephrotoxic tubular necrosis.