Behavior of Vibrio parahemolyticus cocktail including pathogenic and nonpathogenic strains on cooked shrimp

• Vibrio parahaemolyticus cocktail inactivate firstly and then grew rapidly at 10 °C.
• V. parahaemolyticus cocktail decrease λ and increase μmax values from 15 to 30 °C.
• V. parahaemolyticus cocktail decrease |K| values from 4 to 7 °C.
• V. parahaemolyticus cocktail have strong ability to survival at 4–30 °C.
• The strain variability of V. parahaemolyticus was affected to high temperature, 15–30 °C.

Pathogenic Vibrio parahaemolyticus, an important foodborne bacterium, coexists with nonpathogenic strains of V. parahaemolyticus in the environment. However, current predictive models for V. parahaemolyticus usually focused on single strain without considering the pathogenic and nonpathogenic bacteria cocktail coexist situation. In this study, the behavior of four V. parahaemolyticus strains (F18: tlh+/trh+/tdh−, ATCC 17802: tlh+/trh+/tdh−, F36: tlh+/trh−/tdh−, ATCC 33847: tlh+/trh−/tdh+) and their cocktails on cooked shrimp were investigated at different temperatures (4, 7, 10, 15, 20, 25 and 30 °C). Total bacteria counts were enumerated by traditional plate count method, periodically. Results showed both V. parahaemolyticus cocktails and four single strains grew in a temperature range of 15–30 °C and died at 4–7 °C. At 10 °C, for the cocktails, it inactivated at initial 100 h and then grew rapidly; but for single strain, only one strain F18 displayed the similar growth tendency, while the others grew all the time. Compared with single strains, the primary and secondary model analysis showed that the cocktails displayed a better growth activity with higher maximum growth rate and shorter lag time. The above results indicated that modeling bacterial growth by using a cocktail of V. parahaemolyticus strains may be a better option for simulating growth in the real environment. This study will fill in the gap of predictive microbiology and improve significantly the accuracy of microbial risk assessment.