Establishment Of Predictive Model And Risk Assessment Of Vibiro Parahaemolytics In Prawn

Vibrio parahaemolyticus(V. parahaemolyticus) is a Gram-negative and halophilic bacteria that can cause watery diarrhea often with abdominal cramping, nausea, and vomiting, some cause sepsis or even death. Human infections are usually caused by consumption of raw or inadequately cooked aquatic products. China is the largest producer of prawn in the world, and prawn industry accounts for almost 90% of aquaculture in guangxi.Guangxi people love raw seafood such as sashimi, raw prawn.The positive rate of V. parahaemolyticus in prawn is so high that we need to perform the risk assessment of V. parahaemolyticus in prawn.In this paper, the growth and inactivation model of V. parahaemolyticus in prawn was established, the contamination and resistantance of V. parahaemolyticus in prawn in Nanning and the consumption of prawn was investigated. With the data obtained from this paper and other research, based on the microbiological quantitative risk assessment framework, we preliminary perform the quantitative risk assessment of V. parahaemolyticus in prawn from retail to. The main results are as follows:1. The optimum pH for V. parahaemolyticus was 7-9, the optimum salinity was 2%～4% and temperature was 30℃-40 ℃.The growth curve of V. parahaemolyticus was fitted by the modified Gompertz model, modified Logistic model, Baranyi model and Richards model, and demonstrated by the root-mean-squares error (RMSE), bias factor (Bf) and accuracy factor (Af). The results showed that the modified Gompertz model has a better goodness of fit. The Ratkowsky model and the Davey model can well predict the growth rate and the lag time, respectively.The inactivation model was fitted by Weibull model, Linear model and Logistic model. At 5℃, the Weibull model was applied to predict curves of inactive V. parahaemolyticus. At-18℃, the Logistic model can better describe the inactivation rate variation of V. parahaemolyticus.2. Of all the 91 prawn samples, there are 50 samples which have V. parahaemolyticus. And the detectable rate was 54.9%. The geometric mean concentration of V. parahaemolyticus in prawn was 135.3MPN/g. through the nonparametric test, different sampling locations have significant difference (P< 0.05), while the detectable rate have no signigicant difference (P>0.05). Different sampling seasons have significant difference (P<0.05), while the detectable rate have no signigicant difference (P>0.05).Most of the isolated V. parahaemolyticus were highly resistant to amoxicillin and ampicillin, some of them resistant to aminoglycoside, tetracycline, quinolone and other sensive to cephalosporins, chloramphenicol, sulfonamides. The resistant of V. parahaemolyticus is common, and two strains exhibited multidrug-resistance against four kinds of antibiotics. We should increase the regulation of drug use in the process of prawn breeding.3. Use of prediction model and monitoring data, based on the microbiological quantitative risk assessment framework, the incidence rate of illness is 2.432×10-5/person/year. The estimated illness per year was 176 people for Nanning.According to the correlation coefficient, the rank of sensitity of main factors is:the contamination distribution of V. parahaemolyticus in prawn>the temperature from tetail to household> the proportion of eating raw prawns> the transport time from tetail to household>the storage time at home. Thus control the original contamination and the transport temperature of prawns, reduce the proportion of eating raw prawns is the key to control the risk of V. parahaemolyticus.