Author(s): Hideharu Shintani
Many papers published and conducted so far by physical researchers on sterilization using gas plasma exposure. I as microbiologist consider that they overlooked the important points to avoid clumps (overlay of microorganisms, they called clumps as stacking, which is incorrect) in biological indicator (BI) and the importance considering statistical analysis. As a characteristic, microorganisms have themselves significant variation, so number of samples utilized must be necessary to be able to conduct statistical analysis, which concept differed from concept of physical science. The aim of gas plasma sterilization is the death of bioburden and the distribution of bioburden is not seen any clumps in exact status. The penetration depth of gas plasma is around 10 nm, so if BI has clumps (the thickness of BI is around 1 μm) death of inner layer may be hard to attain or delayed, resulting in tailing phenomenon of survival curve or failure of sterility assurance. Physical researchers so often prepare BI by themselves and the prepared BI has significant so-called stacking. As microbiologist calls physical researcher’s attention the importance to conduct experiment using BI free from clumps to attain correct and reproducible sterility result. Furthermore, it is necessary to attain sterility assurance together with material and functional compatibility, otherwise GMP requirement is not achieved.
