STUDIES ON THE SUBUNIT VACCINES OF ESCHERICHIA COLI(SEROTYPE O2)PATHOGENIC TO CHICKENS

The pili of Escherichia coli(serotype O2)pathogenic to chicken were collected,roughly purified and observed under the transmission electron microscope(TEM).The polysaccharides of capsules and the soluble protein of E.coli werealso extracted,and the structural changes of E.coli which occurred during theextraction were observed under TEM.With propolis as adjuvant,the antigens(the collected pili,the extracted polysaccharides of capules and inactivatedwhole bacteria) were used to make three vaccines respectively.Throughchallenging 7-week-old broilers with the same serotype bacteria,the results ofthe protection index,bacteria isolation and lesion score showed that,the cap-sules polysaccharides vaccine was the best of the three,the inactivated wholebacteria vaccine came next,and the pili vaccine third.But 7-week-old broilerschallenged with the different serotype bacteria could not be protected.Theantibody levels of chickens induced by these three vaccines were measured bythe microplate agglutination test.