Abstract: The purpose of this experiment was to evaluate the germicidal efficacy of chlorine dioxide disinfectant developed by our laboratory for dairy teat disinfectant,and to preliminarily study the germicidal mechanism of chlorine dioxide.The germicidal efficacy of chlorine dioxide dairy teat disinfectant was evaluated by quantitative sterilization test.The ultrastructural changes of Staphylococcus aureus after chlorine dioxide treatment were observed by transmission electron microscope (TEM).The changes of cell membrane permeability of Staphylococcus aureus after chlorine dioxide treatment were determined by flow cytometry.The results of quantitative germicidal test showed that when the content of chlorine dioxide in the disinfectant was higher than 1.2 mg/L,the logarithm value of killing Streptococcus agalactiae and Pseudomonas aeruginosa was higher than 3.00,that was,the germicidal rate was higher than 99.9%.When the chlorine dioxide content was higher than 0.6 mg/L,the logarithm of killing Staphylococcus aureus,Escherichia coli and Candida albicans was higher than 3.00,that was,the killing rate was higher than 99.9%.When the content of chlorine dioxide was 0.3 mg/L,it could still effectively kill Staphylococcus epidermidis and Streptococcus dyslactiae.When the chlorine dioxide content was higher than 28 mg/L,the bactericidal rate of Bacillus subtilis could reach 100%.The results of TEM showed that the cell membrane of Staphylococcus aureus treated with 100 mg/L chlorine dioxide for 5 min showed slight shrinkage,and there was a slight gap between the cell wall and the cell membrane,and most of the cells still maintained their original morphology.After treated for 15 min,the morphology of Staphylococcus aureus changed obviously,the cell membrane collapsed obviously,the cell wall completely separated from the cell membrane,and the cytoplasm also agglutinated.Flow cytometry detection results showed that the membrane permeability of Staphylococcus aureus was changed after treated with chlorine dioxide,and the change of membrane permeability was the most obvious after treated with 50 mg/L chlorine dioxide for 15 min.Combined with the results of laboratory evaluation of germicidal efficacy,it was found that the change of cell membrane permeability was only of the causes of killing bacteria.The killing mechanism of chlorine dioxide on bacteria was more complex,and it still needed to be further explored.

Key words: chlorine dioxide; teat disinfectant; evaluation of germicidal efficacy; bactericidal mechanism