Czechowicz S M, Santos O, Zottola E A
Department of Food Science and Nutrition, St. Paul, MN 55108 USA.
Int J Food Microbiol. 1996 Dec;33(2-3):275-84. doi: 10.1016/0168-1605(96)01116-6.
Unheated and heat-stressed (57 degrees C, 50 min and 60 min) cells of Escherichia coli O157:H7, were enumerated using three media supplemented with 1% sodium pyruvate (NaPyr): plate count agar (PCA), tryptic soy agar (TSA) and phenol red sorbitol agar (PhRSA) using the spread plate method. The medium recovering the greatest numbers of severely heated E. coli O157:H7 was PCA with 1% NaPyr. Recovery of heat stressed E. coli O157:H7 on this medium was significantly higher (P < 0.05) than the two other media with pyruvate: 16.3% (50 min heating) and 0.55% (60 min heating) of the total population was recovered with TSA + 1% NaPyr when compared to those numbers found on PCA + 1% NaPyr. The ability of PhRSA + 1% NaPyr to recover heat-stressed E. coli O157:H7 was similar to that of TSA + 1% NaPyr. Using PhRSA + 1% NaPyr media. 12.9% (50 min heating) and 0.61% (60 min heating) of the total population were recovered when compared with the cells enumerated on PCA + 1% NaPyr. Recovery of the heat-stressed cells using the spread plate method was greater than using pour plate method. Recovery was significantly higher (P < 0.05) on the spread plates for highly stressed E. coli O157:H7(1.2 log) heated for 60 min than on the pour plates. Overall, the populations on the TSA spread and pour plates were low compared with the same heat-stressed cells recovered on media containing pyruvate. The
使用三种添加1%丙酮酸钠（NaPyr）的培养基，即平板计数琼脂（PCA）、胰蛋白胨大豆琼脂（TSA）和酚红山梨醇琼脂（PhRSA），通过涂布平板法对未加热以及热应激（57摄氏度，50分钟和60分钟）的大肠杆菌O157:H7细胞进行计数。能回收最多数量严重加热的大肠杆菌O157:H7的培养基是添加1% NaPyr的PCA。在这种培养基上热应激大肠杆菌O157:H7的回收率显著高于另外两种含丙酮酸钠的培养基（P < 0.05）：与PCA + 1% NaPyr上的回收数量相比，TSA + 1% NaPyr回收了总菌数的16.3%（加热50分钟）和0.55%（加热60分钟）。PhRSA + 1% NaPyr回收热应激大肠杆菌O157:H7的能力与TSA + 1% NaPyr相似。使用PhRSA + 1% NaPyr培养基，与PCA + 1% NaPyr上计数的细胞相比，回收了总菌数的12.9%（加热50分钟）和0.61%（加热60分钟）。使用涂布平板法回收热应激细胞的数量多于倾注平板法。对于加热60分钟的高度应激大肠杆菌O157:H7，涂布平板上的回收率显著高于倾注平板（P < 0.05）（高1.2个对数）。总体而言，与在含丙酮酸钠的培养基上回收的相同热应激细胞相比，TSA涂布平板和倾注平板上的菌数较低。
