Strain to strain differences in the growth, survival and adaptation of Vibrio vulnificus and Vibrio parahaemolyticus in broth

Vibrio vulnificus and Vibrio parahaemolyticus are natural inhabitants of estuarine environments of the Gulf of Mexico. V. vulnificus is the leading cause of death, while V. parahaemolyticus is a leading cause of foodborne gastroenteritis from the consumption of seafood in the United States. Refrigeration is commonly used as a preservation method to control the growth of microorganisms in food. The ability of some microorganisms to adapt, as a survival response when exposed to a downshift in temperature, could compromised efforts to use low temperature storage to reduce the risk of foodborne illnesses. Limited research is available on the growth characteristics of different strains of V. vulnificus and V. parahaemolyticus, or on the adaptation response to cold shock on their survival. This study was conducted to determine if strain-to-strain differences exist in the growth and survival of V. vulnificus and V. parahaemolyticus at refrigeration temperatures, and to determine if these strains exhibit a cold temperature adaptation response. Results obtained from this study show that various V. vulnificus and V. parahaemolyticus strains grown in tryptic soy broth have significant differences in growth and survival when stored at 5, 8 or 10°C over 10 days. V. vulnificus strains were able to survive but not grow when shifted from 37°C to storage at 5 or 8°C, while most of these strains were able to grow at 10°C. V. parahaemolyticus strains survived but did not grow when shifted from 37°C to 5°C. During storage at 8 or 10°C however, V. parahaemolyticus strains were able to grow. When these strains were adapted at an intermediate temperature of 15°C for 4 hours, this resulted in an enhanced survival of V. vulnificus strains. This adaptation response however varied between strains. Not all of the V. parahaemolyticus strains had an enhanced survival when exposed to an intermediate temperature of 15°C. The cold adaptation response was more sustained for the V. vulnificus strains at some temperatures tested, while for the V. parahaemolyticus strains that had an adaptation response, this response was generally short lived.