Abstract:

The sterilization effect of pulsed magnetic field treatment on Staphylococcus aureus was examined under different levels of field intensity, pulse number and bacterial suspension temperature. As field intensity increased, the residual survival rate of Staphylococcus aureus generally tended to decrease and the best sterilization effect was observed at a filed intensity of 3.5 T. The effect of pulse number on the residual survival rate of this strain was similar to that of field intensity, and the residual survival rate of this strain reached its minimum after 20 pulses were completed, and then tended to be unchanged with increasing pulse number. Additionally, environmental temperature had a synergistic promoting effect on the inactivation of Staphylococcus aureus. The above results demonstrate that the optimal levels of field intensity, pulse number and bacterial suspension temperature for sterilizing Staphylococcus aureus were 3.5 T, 20 and 30℃, respectively. The percentage of residual viable cells was 7.29% under these conditions. The sterilization of pulsed magnetic field on Staphylococcus aureus displayed a biological window effect. The window value of field intensity under 20 pulse number and 20 window value of pulse number accorded with the following recurrence formula: IW(n) = n(9－n)/4－1 (n is appearing sequence of the window value of field intensity, n = 1, 2 and 3). The comparative analysis of correlation coefficients (R2) of the Gelow, the Weibull and the Hulsheger models indicates that the Gelow model is the best model describing the dynamic change of percentage of residual viable Staphylococcus aureus cells during pulsed magnetic field treatment.

Key words: pulsed magnetic field, Staphylococcus aureus, sterilization, biological window effect, dynamics model