Attenuated Live Fowl Cholera Vaccine II. Some Biological Properties of Strain M-3-G

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Abstract
The attenuated strain M-3-G of Pasteurella multocida was tested for its effect on chicks, turkey poults and Japanese quail of various ages. One day old poults developed no clinical signs when inoculated i.m. with up to 107 colony-forming units (cfu) of this microorganism. Injection i.m. of M-3-G did not affect chicks 5 days old or older although a dry exudate was detected at the inoculation site. No side effects were noted when M-3-G was administered orally to turkeys or chickens. The parental field strain FS-3 of P. multocida kills chicks and poults at 103 cfu and quail at 1-10 cfu. M-3-G was stable for 1 h in tap water and for 4 h in tap water with 5% pasteurized low-fat cow milk added. The minimal immunizing dose was 5 .times. 109-1010 cfu. Low pH rapidly destroyed the microorganism. Neutralizing the gastric acidity did not affect the minimal dose. Survival of the vaccinal strain in the gastrointestinal tract may not be essential to the immunizing process. Antibacterial drugs can apparently be administered parenterally 96 h after vaccination without harming the immunization process. Prevaccination therapy can be performed only after checking the time during which the active antibacterial is present in the bloodstream and tissues at effective levels.