Acquisition of pulsed electric fields resistance in Staphylococcus aureus after exposure to heat and alkaline shocks

作者：Cebrian G; Raso J; Condon S; Manas P^*

来源：Food Control, 2012, 25(1): 407-414.

DOI：10.1016/j.foodcont.2011.10.048

• Pulsed Electric Fields
• Staphylococcus aureus
• stress responses
• cross-resistance
• sublethal damage

Staphylococcus aureus cells were exposed to acid (4.5) and alkaline (9.5) pH, hydrogen peroxide (50 mu M), sodium chloride (10%), heat (45 degrees C) and to a cold shock (4 degrees C) for 2 h and then treated by pulsed electric fields (PEE). Exposing S. aureus cells to acidic, oxidative, hyperosmotic or cold shock conditions resulted in no protection to PEE. By contrast, heat and alkaline shocks increased the resistance of S. aureus cells to PEE, regardless the electric field strength applied, the pH and a, of the treatment medium and the strain and growth phase investigated. A Delta sigB deletion mutant was also able to develop these cross-resistance responses demonstrating that the sigma(B) factor is not necessary for the acquisition of resistance to PEF after exposure to heat and alkaline shocks. When cells were recovered in selective medium (with NaCl added) alkaline-shocked, but not heat-shocked cells, also showed higher PEE resistance than control cells. This investigation contributes to increase the knowledge on the factors determining bacterial PEE resistance and may help in the design of new preservation methods involving PEF.

• 出版日期2012-5