Flores Rolando A, Tamplin Mark L
Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
J Food Prot. 2002 Dec;65(12):1894-902. doi: 10.4315/0362-028x-65.12.1894.
This study determined the distribution patterns of Escherichia coli O157:1H7 in ground beef when a contaminated beef trim was introduced into a batch of uncontaminated beef trims prior to grinding in a small-scale laboratory grinder. A beef trim (15.3 +/- 2 g) was inoculated with a rifampicin-resistant strain of E. coli O157:H7 (E. coli O157:H7rif) and introduced into a stream of noncontaminated beef (322 +/- 33 g) prior to grinding. Seven inoculum levels (6, 5, and 4 total log CFU [high]; and 3, 2, 1, and 0 total log CFU [low]) were studied in triplicate. E. coli O157:H7rif was not detected in 3.1 to 43% of the ground beef inoculated with the high levels or in 3.4 to 96.9% of the ground beef inoculated with the low levels. For all inoculum levels studied, the five ground beef fractions (each 7.8 +/- 0.6 g) with the highest pathogen levels accounted for 59 to 100% of the total pathogens detected. For all inoculum levels, there was a linear relationship between the quantity of ground beef containing E. coli O157:H7rif and the inoculum level. The quantity of E. coli O157:H7rif in the beef remaining in the grinder was proportional to the inoculum level and was related to the location in the grinder. Different components of the grinder accumulated E. coli O157:H7rif in different quantities, with the most significant accumulation being in the nut (collar) that attaches the die to the blade. This study determined specific distribution patterns of E. coli O157:H7rif after the grinding of a contaminated beef trim along with uncontaminated trims, and the results indicate that the grinding operation should be regarded as a means of distribution of microbial contamination in risk analyses of ground beef operations.
本研究确定了在小型实验室研磨机研磨前，将受污染的牛肉切块引入一批未受污染的牛肉切块中时，大肠杆菌O157:H7在绞碎牛肉中的分布模式。取一块牛肉切块（15.3±2克），接种耐利福平的大肠杆菌O157:H7菌株（大肠杆菌O157:H7rif），并在研磨前引入一股未受污染的牛肉流（322±33克）中。研究了七个接种水平（6、5和4个对数CFU总数[高]；以及3、2、1和0个对数CFU总数[低]），每个水平重复三次。在接种高水平的绞碎牛肉中，3.1%至43%未检测到大肠杆菌O157:H7rif；在接种低水平的绞碎牛肉中，3.4%至96.9%未检测到。对于所有研究的接种水平，病原体水平最高的五个绞碎牛肉部分（每个7.8±0.6克）占检测到的病原体总数的59%至100%。对于所有接种水平，含有大肠杆菌O157:H7rif的绞碎牛肉数量与接种水平之间存在线性关系。研磨机中剩余牛肉中的大肠杆菌O157:H7rif数量与接种水平成正比，且与研磨机中的位置有关。研磨机的不同部件积累的大肠杆菌O157:H7rif数量不同，积累最显著的是将模具固定到刀片上的螺母（套环）。本研究确定了受污染的牛肉切块与未受污染的切块一起研磨后大肠杆菌O157:H7rif的具体分布模式，结果表明，在绞碎牛肉操作的风险分析中，研磨操作应被视为微生物污染的一种传播方式。
