Isolation And Identification Of Avian Escherichia Coli And Studies On Trivalent Inactivated Vaccine

Avian colibacillosis is a general term of a class of infectious diseases caused by certain strains of Escherichia coli(E.coli) serotypes. The disease can spread through either breeding eggs vertically,or the digestive tract and respiratory tract by feed,water and air contaminated by the E. coli. Due to the different routes of infection,many diseases on clinic can be caused such as acute septicemia,airsacculitis,pericarditis,perihepatitis,salpingitis,vitelline peritonitis,arthritis,,granulomatous,Dead embryo,enteritis,encephalitis,ophthalmia and so on. In recent years,as the rapid development of the intensive poultry industry in China,the avian colibacillosis is growing worse,and it has become one of the major diseases of poultry industry in China. Effective prevention and treatment of avian colibacillosis have become the key to poultry industry.E. coli bacteria develops resistance to drugs easily,so the effect of the drug treatment to colibacillosis becomes worse and worse with the widespread use of a large number of effective antimicrobial agents and the development of drug resistance. Therefore the development of effective vaccine to prevent avian colibacillosis is taken more and more seriously and have been widely adopted. The antigen of avian pathogenic E. coli is complex,the serotypes are numerous,different serotype strains are lack of complete cross protection and there are great differences among the dominant serotypes of different parts. For the reason that,it is difficult to develop a kind of vaccine which can prevent avian colibacillosis all over the country. The widely adopted method currently is to develop and apply multivalent vaccines in situ,and the practice has proved that application of this method has received very good immune effect.We have surveyed the epidemiology of avian E. coli and successfully isolated 130 strains of E.coli from Liaocheng,Heze,Zhucheng,Weifang,Yantai,Jining regions and so on of Shandong province. Serological results show that the isolated E.coli belong to 13 serotypes,they are O78、O1、O2、O38、O88、O9、O24、O127、O15、O82、O35、O18、O114,accounted for 92.3% of the total number of E. coli strains;10 strains were not identified the serotype, accounted for 7.7% of the total number of E. coli strains.The advantages types are O78、O1、O2,and O78 are 40 strains,O1 are 21 strains,O2 are 15 strains, accounted for 30.8% 、 16.2% 、 11.5% of the total number of E. coli strains respectively.We conducted the animal regression experiment,and picked out the O1、O2、O78 strains of strong virulence to conduct the virulence experiment,screening the QL-003 strain of O1 type、 QL-035 strain of O2 type 、QL-057 strain of O78 type as the system seedlings strains to develop the trivalent vaccine.We have experimented from the aspects of production process, toxicity and immunogenicity on the serotype O1 strain QL-003,serotype O2 strain QL-035,serotype O78 strain QL-057 of avian E. coli,on this basis,we prepared the E.coli trivalent inactivated vaccine 。the vaccine traits, sterile, safety, efficacy, formaldehyde, mercury determination of preservatives residues of inspection, the results are qualified. 3 batches of vaccine after 2months, 4 months, 6 months against poison, type of O1 O78 QL- 057 type strains, O2 QL-035 type strains and O78 QL- 057 strains of tapping the poison of protection are not less than80%(8/10), and controlled chickens were 100%(10/10), shows that our developed 3 price inactivated vaccine immune period for at least six months.