Preservation experiment on frozen-dried Salmonella Pullorum strains

[Objective]The survival rate and biological characteristics of different aged frozen-tried Salmonella pullorum strains were determined in order to provide basic references for the conservation and utilization of Salmonella pullorum strain resources. [Method]For Salmonella pullorum frozen-dried bacteria strains preserved under -20℃ for 15-34 years, the survival rate was determined, the morphology and biochemical characteristics were identified, and the serotype, virulence, and antigenicity of the colony type were detected, respectively. [Result]The results showed that froze-dried strains stored at -20℃ for 15-34 years still have a relatively high survival rates, and the culture characteristics, morphology and biochemical characteristics, and antigenicity between the initial strains and froze-dried strains were not significant. The mutational rate of colony types and serotypes was 8.3%-14.9% and 4.2%-8.7%, respectively. The froze-dried strains could recover its original virulence by rejuvenation through susceptible animals.[Conclusion]Using the freeze-drying method for Salmonella pullorum strains preservation produced high survival rate, and there were no significant biological activity differences between the initial strains and the frozen-dried strains. These findings showed that freeze-drying storage method was suitable for long-term preservation of Salmonella Pullorum.