Effects of heat, acid, and freeze-thaw challenges on survival of starved Vibrio parahaemolyticus in minimal salt medium, tryptic soy broth, and filtered oyster homogenate medium

Vibrio parahaemolyticus is a ubiquitous gram-negative enteropathogenic bacterium. To evaluate the risk of stress-adapted V. parahaemolyticus cells in food, we investigated the survivability of starvation-adapted and starvation-low salinity-adapted cells of this pathogen in different media against different stresses. Logarithmically grown bacterial cells were starved at 25 degrees C in a minimal salt medium with 0.5 or 3.0% NaCl for 24 h. Resistances against challenges of heat, acid, and freeze-thaw treatment exhibited by the starvation-adapted cells were similar to those exhibited by the starvation-low salinity-adapted cells but substantially higher than those of the unadapted control cells. The increased stress resistance of the adapted cells against freeze-thaw challenge was lower in tryptic soy broth than in the starving medium. Resistance of the adapted bacteria against heat and freeze-thaw treatment was completely eliminated in filter-sterilized oyster homogenate medium. Practically, these results help to assess the risk of stress-adapted V. parahaemolyticus in food.