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The Prevalence of Listeria Monocytogenes in Beef Cattle Processing Plants and Thermal Inactivation Model

Author: FengXiaoHui
Tutor: ZhuLiXian；LuoXin
School: Shandong Agricultural University
Course: Agricultural Products Processing and Storage
Keywords: Beef Listeria monocytogenes Serotype Resistance RAPD typing Thermal inactivation model
CLC: R155.5
Type: Master's thesis
Year: 2011
Downloads: 74
Quote: 1
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Abstract

Single increase Listeria monocytogenes (L.monocytogenes, Lm) Listeria (Listeria) is a zoonotic pathogen, is also an important foodborne pathogens one. Beef contaminated Listeria monocytogenes bacteria can cause serious food security problems, a serious threat to human health. In this thesis, a single increase in the popular distribution characteristics of Listeria monocytogenes in beef cattle slaughtering process, while the strains isolated drug sensitivity test, drug study serotypes major virulence genes and molecular typing Phenotypic and genotypic analysis clear genetic relationship of the strains of the different sources. The subject of research ideas to provide solutions for the source of the prevention and control of Listeria monocytogenes, and lay the foundation for our split beef safety. The research content of this paper is divided into three parts. Shandong province three beef cattle slaughter plant (A, B, C plant). Beef cattle slaughtering process in Listeria monocytogenes contamination characteristics in beef production process orders increase the popular features of the Listeria monocytogenes research, sampling The links including cattle feces, fur, peeled body, gutted carcass, carcass after spraying cooling carcass and meat division after seven sessions. According to ISO11290-1, were detected in 116 samples of Listeria monocytogenes Isolation and identification of three beef cattle slaughter plants collected 439 samples, 288 samples in the detection of Listeria monocytogenes, the detection rate was 65.6%; Listeria monocytogenes, the detection rate was 26.4%; plant B detection rate of total detection rate of 94.8%. 2 different factory, different segments of single growth phenotype and genotype studies of Listeria monocytogenes isolates using multiplex PCR method isolates serotypes, drug sensitivity testing using the Kirby-Bauer method, different sources of single PCR method Listeria monocytogenes virulence genes prfA the plcA hlyA, actA, iap carrying case, RAPD method for the study of molecular typing. Derived from three plants of L. monocytogenes is divided into two serotypes C Factory 1/2a, A, B two plants are 1/2c different slaughter plant sources of L. monocytogenes serotype significant regional differences. 55 randomly selected L. monocytogenes isolates for susceptibility testing, they are sensitive to penicillin G, norfloxacin, cotrimoxazole, the the resistance Cefalotin was 1.82%, polymyxin B cefotaxime, enoxacin resistance rates were 25.5%, 36.4%, 38.2%, at the same time there are varying degrees of multiple drug resistance. Single increase in Listeria virulence genes exist in varying degrees lack Overall, 55 single increased 3 missing in Listeria virulence gene, hly, iap and prfA gene were detected; actA genes were not detected in two; plcA genes were not detected in a 55 Listeria monocytogenes can be divided into 34 different RAPD type. 3 beef orders Listeria monocytogenes thermal mismatch live model microbial sterilization study to establish the the microbial prediction model can reduce or replace the routine tests to ensure food safety, has received more and more widely. In order to establish the beef orders increased mechanical model of the thermal inactivation of Listeria monocytogenes, inoculated with three different serotypes beef mixed bacterium Listeria monocytogenes, respectively, at 55 ° C, 57.5 ° C, 60 ° C, 63 ° C, 66 ℃ and 70 ℃ heat treatment under different temperature conditions, g-1 thermal inactivation curves were used Linear model and modified Gompertz model fitting single increase in the number of Listeria monocytogenes from 109CFU? g-1 be decreased to 103CFU? . With the rise of heating temperature, single increase inactivation rates of Listeria monocytogenes in beef gradually increasing D values ??decrease, the Z value of 6.25 ° C. Modified Gompertz model the growth of Listeria monocytogenes inactivation curve better than the Linear model single beef. The establish two model affected by the temperature of the modified Gompertz model parameters, namely lnM = 27.516-0.364T; lnμ = -27.358 0.366T. 59 ℃ and 64 ℃ actual Listeria monocytogenes bacteria survived two models built for validation, correction of the degree of deviation of the Gompertz model (Bf) and accuracy (Af) in the acceptable range, and the modified Gompertz model RMSE value was significantly lower than the Linear model, show that the modified Gompertz model better than the Linear model prediction of heat treatment on Listeria monocytogenes. The Gompertz model established in this study is capable of simulating different temperature (55-70 ℃) of Listeria monocytogenes in beef thermal inactivation.

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CLC: > Medicine, health > Preventive Medicine,Health > Nutrition, hygiene,food hygiene > Food hygiene and food inspection > Food hygiene and inspection
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