Ethanol shock changes the fatty acid profile and survival behavior of Vibrio parahaemolyticus in various stress conditions

Vibrio parahaemolyticus 690, a clinical strain, was subjected to ethanol shock in the presence of 5% ethanol for a period of 30 and 60 min. Survival behaviors of the ethanol shocked and control cells of V. parahaemolyticus in the presence of H2O2 (20 ppm), crystal violet (3 ppm), NaCl (20%), and low pH solution (pH 4.4) containing various organic acids including lactic acid, acetic acid, citric acid and tartaric acid (25 mM) were compared. In addition, the effects of ethanol shock on the fatty acid profile and recovery of V. parahaemolyticus on tryptic soy agar (TSA) plus various amounts of NaCl were also investigated. After ethanol shock, it was found that the proportion of vaccenic acid (18:1) increased, while the proportion of palmitic acid (16:0) and ratio of saturated fatty acid to unsaturated fatty acid decreased in cells of V. parahaemolyticus. The recovery of the ethanol-shocked cells on TSA plus 6.0% or 7.5% NaCl was significantly less than the control cells. Furthermore, ethanol shock increased the survival of V. parahaemolyticus in the presence of H2O2, while made the test organism less resistant to crystal violet, high NaCl and organic acids. The degree of decreased acid tolerance observed on the ethanol-shocked cells of test organism varied with the organic acid examined. Finally, ethanol shock for 60 min exhibited either a higher or similar degree of effect on the test organism (depending on the type of stress encountered) than did ethanol shock for 30 min. Data obtained from the present study does provide useful information that is indispensable when control measure of V. parahaemolyticus is to be performed efficiently and adequately.