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Growth and Heat Resistance Kinetic Variation Among Various Isolates of Salmonella and its Application to Risk Assessment

机译：沙门氏菌不同菌株的生长和耐热动力学变化及其在风险评估中的应用

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摘要

The abilities of cells of a particular type of bacteria to leave lag phase and begin the process of dividing or surviving heat treatment can depend on the serotypes or strains of the bacteria. This article reports an investigation of serotype-specific differences in growth and heat resistance kinetics of clinical and food isolates of Salmonella. Growth kinetics at 19℃ and 37℃ were examined in brain heart infusion broth and heat resistance kinetics for 60℃ were examined in beef gravy using a submerged coil heating apparatus. Estimates of the parameters of the growth curves suggests a small between-serotype variance of the growth kinetics. However, for inactivation, the results suggest a significant between-serotype effect on the asymptotic D-values, with an estimated between-serotype CV of about 20%. In microbial risk assessment, predictive microbiology is used to estimate growth and inactivation of pathogens. Often the data used for estimating the growth or inactivation kinetics are based on measurements on a cocktail―a mixture of approximately equal proportions of several serotypes or strains of the pathogen being studied. The expected growth or inactivation rates derived from data using cocktails are biased, reflecting the characteristics of the fastest growing or most heat resistant serotype of the cocktail. In this article, an adjustment to decrease this possible bias in a risk assessment is offered. The article also presents discussion of the effect on estimating growth when stochastic assumptions are incorporated in the model. In particular, equations describing the variation of relative growth are derived, accounting for the stochastic variations of the division of cells. For small numbers of cells, the expected value of the relative growth is not an appropriate "representative" value for actual relative growths that might occur.
机译：特定类型细菌的细胞离开滞后阶段并开始分裂或存活热处理的过程的能力可能取决于细菌的血清型或菌株。本文报告了沙门氏菌临床和食品分离株生长和耐热动力学的血清型特异性差异调查。使用浸没式盘管加热装置在脑心浸液中检测了19℃和37℃下的生长动力学，并在牛肉肉汁中检测了60℃下的耐热动力学。生长曲线参数的估计表明，生长动力学的血清型之间存在很小的差异。但是，对于灭活，结果表明血清型之间对渐近D值有显着影响，估计血清型之间CV约为20％。在微生物风险评估中，预测微生物学用于估计病原体的生长和灭活。通常，用于估计生长或灭活动力学的数据是基于对鸡尾酒的测量，该鸡尾酒是大约等比例的几种血清型或所研究病原体菌株的混合物。从使用鸡尾酒的数据得出的预期增长或失活率有偏差，反映了鸡尾酒增长最快或最耐热的血清型的特征。在本文中，提供了一种减少这种可能的风险评估偏差的调整措施。本文还讨论了将随机假设纳入模型时对估计增长的影响。特别是，得出了描述相对生长变化的方程式，说明了细胞分裂的随机变化。对于少量细胞，相对生长的预期值对于可能发生的实际相对生长而言不是适当的“代表”值。

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