Townsend D E, Irving R L, Naqui A
IDEXX Laboratories, Inc. Westbrook, ME 04092-2041, USA.
J Food Prot. 1998 Apr;61(4):444-9. doi: 10.4315/0362-028x-61.4.444.
SimPlate for coliforms and Escherichia coli (CEc) is a new method for the detection and quantification of coliforms and E. coli in food. Internal validation of the method was carried out at IDEXX Laboratories (Westbrook, ME) with 180 food samples representing a variety of different food matrices and compared against three-tube MPN (most probable number), VRBA (violet red bile agar) + MUG, and Petrifilm (E. coli count) methods. SimPlate CEc was highly correlated with each of these methods for the quantification of coliform bacteria (r > or = 0.90). An insignificant number of food samples were found to contain E. coli; therefore, no meaningful correlation data could be generated. Four hundred forty-four additional food samples were tested at five collaborating laboratories for the presence of coliforms E. coli using SimPlate CEc and either VRBA + MUG or Petrifilm (E. coli count). Regression analysis of data from SimPlate for CEc versus Petrifilm E. coli count plates generated correlation coefficients (r) of at least 0.89 for total coliforms and at least 0.90 for generic E. coli. Correlation coefficients between SimPlate for CEc and VRBA + MUG data were at least 0.90 for coliforms and at least 0.86 for E. coli. SimPlate for CEc demonstrated better recovery of E. coli than Petrifilm when high populations of bacteria were present. E. coli was not detected in 20 or 50 (40%) raw milk samples tested by the Petrifilm method due to the presence of interfering coliform and noncoliform bacteria. It is concluded that SimPlate for CEc is a suitable alternative for determining numbers of coliform bacteria and E. coli in food.
用于检测和定量食品中大肠菌群和大肠杆菌的SimPlate（CEc）是一种新方法。该方法在IDEXX实验室（缅因州韦斯特布鲁克）进行了内部验证，使用了180个代表各种不同食品基质的食品样本，并与三管MPN（最可能数）、VRBA（紫红胆盐琼脂）+MUG和Petrifilm（大肠杆菌计数）方法进行了比较。SimPlate CEc与这些方法中的每一种在定量大肠菌群方面都高度相关（r≥0.90）。发现少量食品样本含有大肠杆菌；因此，无法生成有意义的相关性数据。另外444个食品样本在五个合作实验室使用SimPlate CEc以及VRBA+MUG或Petrifilm（大肠杆菌计数）检测大肠菌群和大肠杆菌的存在情况。对CEc的SimPlate与Petrifilm大肠杆菌计数平板的数据进行回归分析，得出总大肠菌群的相关系数（r）至少为0.89，普通大肠杆菌的相关系数至少为0.90。CEc的SimPlate与VRBA+MUG数据之间的相关系数，大肠菌群至少为0.90，大肠杆菌至少为0.86。当存在大量细菌时，CEc的SimPlate对大肠杆菌的回收率比Petrifilm更好。用Petrifilm方法检测的20个或50个（40%）生牛奶样本中未检测到大肠杆菌，原因是存在干扰性的大肠菌群和非大肠菌群细菌。结论是，CEc的SimPlate是测定食品中大肠菌群和大肠杆菌数量的合适替代方法。
