The Development Of Clostridium Perfringens Type-A Infection Model In Rabbit

In recent years, many rabbit warrens frequently outbreak diarrhoea enteritis in our country, which mainly caused by Clostridium perfringens(Cl. Perfringens)type-A. It is a bowel disease which caused great economic losses in rabbit warrens. The process of the disease is very quick. The mortality is so high that the rabbits do not have time to be treated.So it is very important to prevent the disease. This test is to develope the rabbit infection model of Cl. Perfringens type A, which is not only good for the inspection of Clostridium perfringens vaccine and the evaluation of antitoxin therapeutic effect, also good for evaluating the virulence of strains, for the study of pathogenesis and treatment of Cl.perfringens.By isolating bacteria, staining and microscopic examination, separation and purification,biochemical experiment and multiple PCR genotype identification the strains isolated in the clinical cases is preliminarily diagnosed of Cl. perfringens type-A. Fore strains which are isolated from rabbit liver in the clinical cases are identified of Cl. perfringens type-A. Strains of Cl. peringens type-A from clinical cases and standard strain NCTC 528 drew a comparison in the lecithin enzyme hydrolysis activity experiments and the injection of mice LD50 experiments afer recovery strains, propagation of bacteria and toxin producing. Strains NCTC528 and isolates 3 is in the same better toxin-producing conditions to establish the rabbit infection model of Cl. perfringens type-A.NCTC 528 and separation strains 3 after recovery, enrichment and toxin producing,whose cultures are used for infecting the rabbits. Cultures administered by different processing methods, different infection ways to infect 2kg-healthy rabbits. The result shows that the intraperitoneal injection of exotoxin NCTC528( LD50:24.25; lecithin enzyme hydrolysis activity:24)can lethal the rabbit at 6-8 hours whose minimum rabbit lethal dose is3ml; Intramuscular injection of exotoxin NCTC528(LD50:24.25; lecithin enzyme hydrolysis activity:24)whose minimum lethal dose is 4ml. And intramuscular injection of the bacterium liquid( bacterium liquid concentration:1.3x109cfu/ml; LD50:25.25; toxins lecithin enzymehydrolysis activity:25)minimal lethal dose is 3ml. The dead rabbits which are infected of exotoxin by abdominal cavity injection and muscle injection are autopside and observed of histopathological lesions. Lesions mainly characterized by: intraperitoneal and intramuscular sterilization toxins have emerged gastric mucosal shedding and intestinal diffuse bleeding.But the gastric mucosal ulceration and cecum serosal surface have rare bleeding lesions.Culture medium whose bacterium liquid concentration is 1.3x109cfu/ml and lecithin enzyme hydrolysis activity titer is 25 respectively gavages 2kg-healthy rabbit in different dose(30ml, 40 ml, 50ml)using different feed formula. Results only have short-term diarrhea, not producing deaths. 2kg-healthy rabbits are infected bacteria through ways of ileum injection(bacterium liquid concentration: 1.6 x 108cfu/ml; lecithin enzyme hydrolysis activity: 24)resulting of part of the rabbits appeared diarrhea and didn’t copy lesions stably. Blood routine examination found that the total lymphocyte ratio, the platelet and white blood cells are significantly higher than normal after one week, that demonstrated inflammation reaction in the body. The toxin antibody titer of rabbits’ serum three weeks after infection messured1:200-1:400. It is found that Cl. perfringens is not a dominant strains in the intestinalcolony analysis(jejunum、ileum、cecum).