Characterization Of Campylobacter Strains Isolated From Livestock And Poultry And Evaluation Of Inactivated Whole-cell Vaccine Of Campylobacter Jejuni

Campylobacter is one kind of Gram-negative bacteria with microaerobic,curved or spiral bacteria,mainly including Campylobacter jejuni and Campylobacter coli,in which C.jejuni accounts for more than 90%of human campylobacteriosis.C.jejuni mainly causes human diarrhea enteritis and is closely related to human autoimmune diseases such as Guillain Barre syndrome.Infected livestock show symptoms of abortion,infertility,mastitis and diarrhea of young animals.Infected poultry does not show any clinical symptoms.C.jejuni has become the main source of human infection.In view of the important role of poultry infection of C.jejuni in foodborne pathogen,reducing the load of C.jejuni in poultry is one of the key strategies to control the risk of human infection.For this reason,this experiment firstly identified the biological characteristics of Campylobacter strains isolated from livestock and poultry,and then prepared the inactivated whole-cell vaccine by using the C.jejuni reference strain NCTC 11168.The chickens were immunized to evaluate the effects of the vaccine on the colonization of C.jejuni in the chicken intestine through oral challenge,The results will be helpful for the prevention and control of C.jejuni in poultry.Firstly,112 Campylobacter strains were identified by multiplex PCR,including73 C.coli strains from pigs,33 C.jejuni strains from chicken,3 C.jejuni strains from duck,2 C.jejuni strains and one C.jejuni strain from bovine.The results of the antimicrobial resistance test showed that Campylobacter isolates had varying degrees of resistance to different types of antibiotics,mainly including the resistance rate of ciprofloxacin with 92.0%,naphthyridic acid 88.4%.The most sensitive antibiotic to Campylobacter strains was carbapenem antibiotic imipenem,and the resistance rate was only 2.6%.The results showed that 78 strains（69.6%）of Campylobacter coli had motility,and the proportion of Campylobacter coli from pigs was greater.The biofilm assay showed that 10 Campylobacter strains had strong biofilm forming ability（8.9%）;66 strains of Campylobacter had medium biofilm forming ability（59.0%）.Currently,no commercial vaccines were used to inhibit or reduce the colonization of C.jejuni in poultry.This study aims to develop a vaccine that can reduce C.jejuni colonization in chicken intestines.A novel inactivated agent of H₂O₂ and Cu Cl₂mixture was used to inactivate C.jejuni NCTC 11168 and prepare an oil adjuvant inactivated vaccine for SPF chickens immunization.The induced anti-Campylobacter specific antibody level was measured.The effect on C.jejuni colonization in the chicken ceca was evaluated by oral challenge.The transcriptional level of cecal cytokines and the cecal villus length and crypt depth were also determined.The results showed that the inactivated whole-cell vaccine could induce specific serum Ig G and bile Ig A,but could not inhibit or reduce the colonization level of C.jejuni in chicken ceca,and no significant effects were observed on the cecal villi and crypts with C.jejuni challenge.For the majority of cecal cytokines,there was no significant difference in the transcriptional level before challenge and 1 day post inoculation（DPI）,but increased significantly at 10 DPI.Comparison on the cecal samples at the same age showed that the transcriptional levels of some cytokines in the adjuvant immunization group and the whole-cell immunization group were significantly higher than those in the blank control group.Although the inactivated whole-cell vaccine could induce the production of high-level specific antibodies,it didn’t inhibit the colonization level of C.jejuni in chicken cecum.The colonization mechanism of C.jejuni in chicken cecum needs to be further explored.