Application of MALDI-TOF MS in the study of bacterial contamination of worn masks
Objective To analyze the bacterial contamination of masks with different wearing times by the matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS),and to provide a basis for the relevant departments to propose a reasonable wearing time of masks.Methods In July 2022,volunteers were recruited to wear masks in their daily work environments for wearing times of 0.5h,1.0h,2.0h,4.0h and 5.0h,respectively.The total bacterial count on the inner and outer surfaces of the masks at different wearing times was determined by the pour plate method;the bacterial abundance on the inner and outer surfaces of the masks was identified and analyzed by the MALDI-TOF MS method.Statistical analyses were performed using the adjusted F-test method.Results There was a statistically significant difference in the total bacterial counts between the inner surface and the outer surface of the mask worn for 5.0h[mean deviation(MD)=380.9,P＜0.001].There was no statistically significant difference in the total bacterial counts between the inner surface and the outer surface of the masks worn for 0.5h,1.0h,2.0h and 4.Oh(MD=9.2,P=0.704;MD=9.3,P=0.701;MD=40.2,P=0.099;MD=19.O,P=0.433).A total of 320 single colonies were isolated throughout the study.The number of bacterial genera detected simultaneously on the inner and outer surfaces of masks worn for 4.0h was 2,with a top penetration rate of 33.3％.The number of bacterial genera detected simultaneously on the inner and outer surfaces of masks worn for 5.0h was 5,with the penetration rate of 25.0％to 100.0％.Conclusion The total bacterial count on both the inner and outer surfaces of the masks increases with longer wearing times.The number of bacteria on the inner surface of the mask is higher than that on the outer surface of the mask for the same wearing time,and the bacterial species on the inner surface of the mask is lower than that on the outer surface.It is recommended to replace the mask when wearing it for more than 4.0h.
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