Isolation, Bionomics Of Bdellovibrio From Broiler And Its Therapeutic Test To Pullomm Disease

The contents of caecum and rectum of 30 healthy broilers were collected by aseptic method. One kind of bacterium which could prey on other bacteria was isolated using E. coli O₈ as host. It was judged as Bdellovibrio by its morphological characteristics and bionomics and was named as BdSA12. Standard strain 109J was used in the following research. BdSA12 and 109J were treated with different pH acid liquor for 2 hours. Both the number of survival BdSA12 and 109J decreased very significantly when pH decreased. The lowest pH they could tolerate was 3.0 and 4.0 respectively. BdSA12 and 109J were cultivated with medium (including bile salt ranged in 0.10-0.60%). Both the number of survival BdSA12 and 109J decreased very significantly as the concentration of bile salt increased. The highest concentration of bile salt they could tolerate were 0.40% and 0.30% respectively. When BdSA12 was cultivated at different temperature, the survival number was 10⁵pfu/mL if temperature ranged from 28 ℃ to 39℃and decreased as the temperature increased beyond 39℃. The number of 109J was 10⁵pfu/mL when the cultivating temperature was 28 ℃. The highest temperature BdSA12 and 109J could tolerate was 42℃and 38℃ respectively. The result of antibiotic susceptibility test showed that 109J was sensitive to all the tested antibiotics and BdSA12 was sensitive to all the other tested antibiotics except carboxybenzyl penicillin during 48 hours. Using different bacteria as hosts, both BdSA12 and 109J could prey on all the Gram-negative bacteria and a minority of Gram-positive bacteria. They also could prey on the heated bacteria Such as E. coli O₈, E. coli O₁₄₉, E. coli O₁₅₇, E. coli ATCC 65922, S. pullorum C79-13 and S. typhimurium. Bdellovibrio formed plaques quickly.The safe test was carried out through drenching Kunming mice with 10⁵pfu/mL BdSA12. All the mice of test group and control group were healthy. This result showed BdSA12 was safe to mice. The mice artificial infected with S. typhimurium were cured by BdSA12, and the survival rate was 90%. The number of Bdellovibrio in the mice's dejecta increased as the drenching times increased. The maximum was 10⁴pfu/g. After the course of treatment, the number decreased to 10²pfu/g gradually.The broilers of 2-day-old were artificial infected with 10ncfu/mL S. pullorum by drenching for 4 days consecutively and almost all the broiler caught seak. The broilers were treated through drenching with 105pfu/mL BdSA12, 103pfu/mL BdSA12, and 60mg/mL neomycin. At the same time, a infected and non-cure group and a health group were settled. The death rates were 50%, 60%, 40%, 80% and 0 respectively. The result showed that BdSA12 played an important role in the treatment to Pullorum to some extent. The shift of S. pullorum were detected by isolating the bacterium from broilers's heart, liver, spleen and cholecyst. The results showed that 105pfu/mLBdSA12 group, neomycin group and the health group had no shift of S. pullorum, one broiler in 103pfu/mL BdSA12 group had S. pullorum's shift, all broilers of infected and non-cure group had S. pullorum's shift. Compared with the microbial population of intestinal tract of health group, the numbers of both E. coli and Lactobacillus of neomycin group were sharply decreased, the number of E. coli of 10 pfu/mLBdSA12 group was sharply decreased and the number of lactobacillus hadn't conspicuous changes, the number of E. coli of 103pfu/mLBdSA12 group hadn't conspicuous changes and the number of lactobacillus sharply decreased.From the result of the treatment for Pullorum, it is concluded that BdSA12 is effective to cure this disease and it might have widely-used prospective.