Method for the detection of injured Vibrio parahaemolyticus in seafoods

The sensitivity of Vibrio parahaemolyticus cells to refrigeration and frozen storage and the development of a method for detecting injured and uninjured V. parahaemolyticus cells were studied. Cell suspensions in different kinds of seafood homogenates were either regrigerated (4 degrees C) or frozen (-20 degrees C), stored, and examined for cell survival during storage. V. parahaemolyticus cells were sensitive to both storage temperatures. Many cells died, and many survivors were sublethally injured. In general, refrigeration storage appeared to be more injurious than frozen storage. The initial recovery of the sublethally injured cells was highest in a nutritionally rich, nonselective liquid medium such as Trypticase soy broth, whereas maximum cell multiplication was observed in Trypticase soy broth containing 3% NaCl. The sublethally injured V. parahaemolyticus cells demonstrated sensitivity to the selective enrichment medium, glucose salt teepol broth. From these findings, a new method (designated as the "repair-detection" method) was developed for the isolation and enumeration of V. parahaemolyticus. Comparative studies between the recommended and the repair-detection methods showed that injured V. parahaemolyticus cells were present in commercial seafoods and that the repair-detection method was definitely more effective for the detection of total numbers of V. parahaemolyticus cells.