Inactivation of Escherichia Coli using the plasma needle

We present a parameter study on deactivation of Escherichia Coli (E. Coli) by means of a non-thermal atmospheric plasma needle. One of the intended applications of plasma needle is treatment of dental caries. We use E. Coli films as a model system and optimize the conditions for bacterial destruction. Plasma treatment of E. Coli films results in formation of a bacteria-free void with a size up to 12 mm. 104 - 105 colony forming units are destroyed after 10 s of treatment. Prolongation of treatment time and usage of high powers do not significantly improve the destruction efficiency: short exposure at low plasma power is sufficient. Furthermore, we study the effects of temperature increase on the survival of E. Coli and compare it with thermal effects of the plasma. The population of E. Coli heated in a warm water bath starts to decrease at temperatures above 40 °C. Sample temperature during plasma treatment has been monitored. Thermal effects cannot account for bacterial destruction at low-power conditions. For safe and efficient in vivo disinfection, plasma power and treatment time should not exceed 150 mW and 60 s, respectively.