Bacterial deactivation using a low temperature argon atmospheric plasma brush with oxygen addition

This study investigated the bacterial deactivation effects of a low temperature atmospheric argon plasma brush with oxygen addition. Two types of bacteria, Escherichia coli (E. coli) and Micrococcus luteus (M. luteus) seeded in various media were exposed to the oxygen enriched gas plasma and their survivability were thoroughly examined under various plasma conditions. It was found that the bacterial deactivation capability of the plasmas was highly dependent on the amount of oxygen addition and the type of supporting medium. With filter paper as the supporting medium, the addition of oxygen into the argon plasma system led to significant improvement in the bacterial killing efficacy, compared with an argon only plasma discharge. With oxygen addition, the plasma treatment time for a complete kill of the bacteria was 2 min for E. coli and 1 min for M. luteus. These are much shorter than the times required with argon only plasmas. When a nutrient broth or standard methods agar were used as the supporting medium, however, a longer plasma treatment time was necessary when using plasmas with the oxygen addition. The changes in bacterial cell structure after plasma exposure were examined using scanning electron microscopy. The change in plasma characteristics with oxygen addition was investigated using optical emission spectroscopy. The possible mechanism for bacterial inactivation of the plasmas is also discussed here.