Application of modified vacuum freeze-drying technology in the preparation of bacterial slices for sterilization test of disinfectants
Objective To study a method of improving the preparation of bacteria tablet in disinfectant sterilization test by vacuum freeze-drying technology.Methods The improved vacuum freeze-drying technology was used to prepare the vacuum freeze-dried bacteria tablets by fixation of Escherichia coli and Candida albicans on the carrier.The storage period monitoring test,stability simulation test and carrier quantitative sterilization test were used to evaluate the storage period and stability of the vacuum freeze-dried bacteria tablets and whether they affected the disinfection effect.Results Under the storage condition of-20 ℃,the validity period of Escherichia coli and Candida albicans bacterial tablets was 3 months when the carrier type was cloth and steel tablets.Cloth tablets of Escherichia coli and Candida albicans were stored for 4 months at-80 ℃,while steel tablets had the best stability and were stored for 6 months.With the transportation tempera-ture not higher than 25 ℃ and transportation time not more than 4 h as well as the neutralizer immersion temperature not higher than 25 ℃ and immersion time not more than 4 h,the recovered bacterial amount of vacuum lyophilized bacterial tablets could still meet the test requirements.The bacteria tablets were prepared by conventional drying method and vacu-um freeze-drying method,respectively.When 84 disinfectant with an effective chlorine content of 150 g/L was used for 3 min,the logarithm of killing of Escherichia coli in the 2 methods was more than 3.00.When 84 disinfectant with an effec-tive chlorine content of 150 g/L was used for 5 min,the logarithm of killing value of Candida albicans in the 2 preparation methods was more than 3.00.When 100 g/L peracetic acid disinfectant was used for 1min,the logarithm of Escherichia coli killing was more than 3.00 in the two preparation methods.Using 100 g/L peracetic acid disinfectant for 3 minutes,the logarithm of killing Candida albicans in the 2 preparation methods was more than 3.00.Conclusion The improved vacuum freeze-drying technology can obviously prolong the storage time of vacuum freeze-drying bacteria tablets and main-tain good stability.
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