Toxin Production by Isolates of Corynebacterium pseudotuberculosis and Development of A Protective Product

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Mohamed Bakri Abdel Wahab Mohamed, Mohamed
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A total of 43 isolates of Corynebacterium pseudotuberculosis were obtained from specimens collected at Nyala slaughterhouse. Eleven of these were selected for further study to determine their potentiality for high cell yield (cfu) and good haemolytic activity. One isolate (CP41N) was found to give the best cell yield and the highest haemolytic titre. It was used for preparation of cell wall (CW), cell wall lysate immunogen, toxoid and challenge. Following preparation of CW lysate and toxoid, protein content was determined for both. The CW lysate vaccine contained 8 mg protein per dose. The other vaccine was composed of CW lysate (8 mg protein) plus toxoid (1 mg/ml) which was used as adjuvant. Three doses of each vaccine with one-month interval were injected s/c in two groups of goats of (9-16 kg weight), five animals in each. The third group was left as unvaccinated control. The immunological response was monitored by using bacterial agglutination and haemolysis inhibition tests. The primary response peak was observed after two weeks from the first dose of both CW lysate and CW lysate +toxoid in vaccinated animals. After the second and third doses, the corresponding peaks were observed after one week following vaccination. Three weeks after the last vaccine dose, all animals were challenged i/v by 1.2X105 CFU/ml of C. pseudotuberculosis CP41N. Then, one month after challenge all animals were slaughtered and examined for CLA lesions. There was a significant reduction (P < 0.01) in lesions in animals vaccinated with CW lysate and CW lysate +toxoid compared with the controls. On the other hand, there was a significant reduction (P < 0.05) in the number of lesions in animals vaccinated with CW lysate+toxoid compared with animals vaccinated with CW lysate alone. After challenge, two animals died from both CW lysate vaccinated group and control group (40%). Whereas in the CW lysate vaccinated and control animals lesions were found in all animals (100%). The percentage of lesions in internal organs (lungs, livers, spleens, kidneys, pericardia, omenta, mediastinal and mesenteric lymph nodes) was 20%, 30%, and 57.5% for CW lysate + toxoid, CW lysate vaccinated animals and controls, respectively. It is concluded that CW lysate + toxoid vaccine is a very promising product for protection against caseous lymphadenitis taking into consideration the high challenge dose and the route of administration.
Toxin Production by Isolates of Corynebacterium pseudotuberculosis and Development of A Protective Product