接种量对单增李斯特菌生长/非生长界面的影响

The Effect of Inoculum Levels on Growth/No Growth Interface of Listeria monocytogenes

在4个水平（10~1,10~3,10~5,10~7 CFU/m L）接种浓度下,通过肉眼观察培养基浊度结合涂布TSA-YE平板,对TSB-YE肉汤中培养的单增李斯特菌在温度（0~30℃）、盐度（0.5%~8.5%）、pH（4.0~7.5）条件下的生长/非生长响应进行测定,结果表明：接种量影响单增李斯特菌生长/非生长界面的位置。通过对各种生长条件下单增李斯特菌生长/非生长数据的分析,用多项式逻辑回归模型,建立单增李斯特菌生长/非生长的界面模型,模型拟合的一致性为83.8%到89.6%,拟合结果较好。接种量对微生物生长的起点有重要影响,为微生物生长受初菌数的影响提供定量分析数据,也为建立实际产品中微生物的生长/非生长界面模型提供参考依据。

The growth/no growth responses of Listeria monocytogenes inoculated at four levels（101,103,105,107CFU/m L） into tryptic soy broth added with 0.6% yeast extract（TSB-YE） were monitored at different combinations of temperature（0-30 ℃）, NaCl concentration（0.5%-8.5%） and pH（4.0-7.5）. The study was carried out on tryptic soy agar added with 0.6% yeast extract（TSA-YE） plates and growth was monitored visually by observing the turbidity of the medium combined with plate counts. The growth limits of the pathogen and hence the position of the growth boundary were found to be affected by the inoculums size, the difference in the growth limits between the tested inoculum levels was higher in environments where a single factor（pH or aw） was inhibitory than in environments where pH and aw together were inhibitory. The data were used to develop a growth/no growth interface model for each inoculum level tested, using logistic polynomial regression. The concordance indices of the models ranged from 83.8% to 89.6% and showed a good fit to the observed data in all models. This study indicates the importance of inoculum size for microbial growth initiation and provides quantitative data that show how the combinations of hurdles which prevent growth vary with inoculum size, and provide inferences for further modeling growth/no growth interface of microbial population in practice.