The Serial Subcultivation Of GN52 And The Research Of Drug Resistance Of Riemerella Anatipestifer Isolates

Riemerella anatipestifer (RA) infection is a serious worldwide problem of natural waterfowl and domestic turkey, duck and goose populations. The infection typically exacts a severe economic cost, especially when poultry is also infected with other microorganisms. Mortality and morbidity rates are usually between 10 and 30%, but mortality of as high as 75% has been recorded in infected duck farms. Once the disease invades duck and goose flocks, it can become endemic. Eradication can be difficult, with repeated infectious episodes possible. Till now, at least 21 serotypes of R. anatipestifer have been isolated in the world and there's no cross protection among each serotypes.Usually, using antibiotics correctly is an effective way to cure this disease, but it became failed because RA came into being resistance to various antibiotics easily. So immunization becomes the best way in proventing the disease. It is important to make sure the super serotype because there's no cross protection among serotypes.GN52 whose serotype was 10 isolated from GuangDong was studied in this experiment. Serotype 10 is super serotype of GuangDong. GN52 was passaged on the Martin Medium successively according to its optimum condition. Had been done experiments included Gram staining, biochemical test, drug sensitivity test and animal experiments on the bacteria of different generation. It was indicated that the characters of the bacteria was stably. And then GN52 was inactivated and mixed with propolis and oil. The antigen quantity is 50×108CFU/ml. The 7-day-old cherry valley ducks were immuned the two inactivated vaccines after vaccined and determined the conservancy rate respectively. The results showed that the vaccined effect of oil-emulsion vaccine was the best, it achieved the biggest protective efficacy in the 14th day after vaccined. The 7-day-old cherry valley ducks were immuned with oil-emulsion vaccine, the dosages were 0.05ml one duck, 0.1ml one duck and 0.3ml one duck. It was challenged in the 14th day after vaccined. It showed that the minimum immunizing dose≤0.1ml one duck.FQNS has been used in the treatment during these years, so drug resistence became seriously. In order to approach the drug fast mechanism, the 31 RA strains'MIC were determined using broth dilution method and gyrA QDRD area of 31strains was sequenced in order to look for mutational hot spot and law. It was discovered that 26 strains were midranging drug ones, even 19 strains were serious drug fast ones to ciprofloxacin. 27 strains were serious drug fast ones, 3 strains were midranging drug ones and only 1 strain was sensitive to norfloxacin. 25 strains were above midranging drug ones to the two drugs among 31 strains which was amount to 80.6%. The gyrA gene of all of the 31 strains of norfloxacin drug fast ones were mutated and the amino acids also changed (Ser83→Ile83/Arg83,Gly87→Asp87), and the gene mutation of drug resistant strain of ciprofloxacin drug fast ones had no obviously regularity.