Plasma sterilization - Methods and mechanisms

Sterilization with a plasma (ionized gas) enables one to inactivate 106 B. subtilis spores in less than 10 minutes, when these are in direct contact w ith the plasma, or in approximately 40 minutes, when they are exposed to th e gas flow coming from the plasma source (spatial afterglow regime). The su rvivor curve. which is a plot of the logarithm of the number of living spor es as a function of the treatment time, is characterized. in the case of pl asma inactivation. by the presence of two or three linear segments. in cont rast to sterilization with an autoclave or dry heat, which yields just one straight curve. Plasma sterilization, which can be realized with an Ar-O-2 or N-2-O-2 mixture, is the result of a synergy between oxygen atoms (produc ed by the dissociation of O-2 in the plasma) and UV photons (emitted by ato ms or molecules excited by the plasma). such a synergy being responsible fo r the particular shape of the corresponding survivor curves.