In vitro and in vivo survivality of gdhA derivative Pasteurella multocida B:2

Aims: This study was carried out to determine the in vitro and in vivo survival pattern and period for the newly created gdhA derivative Pasteurella multocida B:2. Methodology and results: For the in vitro study, the gdhA derivative Pasteurella multocida B:2 was cultured in BHI and stored at 4 °C and at room temperature (27 °C). This was followed by determination of the colony-forming unit (CFU)/ mL at weekly intervals. When kept at 4 °C, the bacterial concentration (CFU/mL) showed insignificant (p 0.05) weekly reduction until week 3. By week 4, the concentration was less than 10^2 CFU/mL. In the in vivo study, the derivative was injected intraperitoneal into a group of mice and compared with the group injected intraperitoneal with wild-type P. multocida B:2 and another control group injected with PBS. It was found that the gdhA derivative P. multocida B:2 remained intact for a period of 8 h, lost its kanamycin casette after the 8-h period but remained avirulent throughout the 96 h study period when none of the mice died. On the other hand, all mice that were exposed to the wild-type P. multocida B:2 were dead within 24 h post-injection. Conclusion, significance and impact study: The gdhA derivative P. multocida B:2 seemed to survive better when kept at 4 °C and survived in the host for at least 4 days without returning the virulency. These are important since this strain can be used as live vaccine in animals with minimal possibility of returning back to virulent strain while the l ive vaccine can be stored at 4 °C for at least 4 weeks.