Effect of Low-temperature Stock on the Growth of Bacteria.

It is necessary to know the appropriate bacterial culture temperature and stock temperature to carry out high-precision preservative efficacy tests. In this study, we investigated whether the temperature conditions within the culture or stock affect the survivability or growth activity of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. We found that the cold stocking condition affected the survivability of P. aeruginosa, but not that of E. coli and S. aureus. Furthermore, stocking temperature affects the growth activity of E. coli, P. aeruginosa and S. aureus, and the effect on P. aeruginosa was greater than that on the others. However, the attenuating effect on P. aeruginosa was reversed by culturing into fresh medium for up to six weeks after stocking. These results suggest that cold stress during stocking may affect the growth activity of P. aeruginosa. The results of this study should provide knowledge for the precise evaluation of preservative efficacy in cosmetics.