Pierson C J, Emswiler B S, Kotula A W
Meat Science Research Laboratory, Federal Research, United States Department of Agriculture, Beltsville, Maryland 20705.
J Food Prot. 1978 Apr;41(4):263-266. doi: 10.4315/0362-028X-41.4.263.
Seven recommended methods for estimation of coliforms, three for fecal coliforms and four for enterococci were tested on 30 retail ground beef samples. Lauryl sulfate tryptose broth gave higher coliform counts than did MacConkey's broth or brilliant green lactose bile broth 2% in 3-tube Most Probable Number (MPN) methods. With all MPN broths, coliforms counts were significantly (P ⩽0.05) higher after 48 than after 24 h of incubation. Presumptive coliform counts were higher with surface-overlay plating on violet red bile agar than with pour plating on the same agar or with the MPN broths. However, presence of Escherichia coli Type I was not confirmed as often from the agar medium as the broths. For estimation of fecal coliforms, counts did not differ significantly (P ⩽0.05) between EC broth (45.5 C) and brilliant green lactose bile broth 2% (44 C). Enterococci counts varied significantly (P ⩽0.05) among the four methods.
对30份零售绞碎牛肉样本测试了7种推荐的大肠菌群估算方法、3种粪大肠菌群估算方法和4种肠球菌估算方法。在3管最大可能数（MPN）法中，月桂基硫酸盐胰蛋白胨肉汤培养出的大肠菌群数高于麦康凯肉汤或2%煌绿乳糖胆盐肉汤。使用所有MPN肉汤时，培养48小时后的大肠菌群数显著（P⩽0.05）高于培养24小时后的数量。在紫红胆盐琼脂上进行表面覆盖平板接种时，推定大肠菌群数高于在相同琼脂上进行倾注平板接种或使用MPN肉汤时的数量。然而，从琼脂培养基中确认I型大肠杆菌存在的情况不如从肉汤中常见。对于粪大肠菌群的估算，EC肉汤（45.5℃）和2%煌绿乳糖胆盐肉汤（44℃）之间的计数差异不显著（P⩽0.05）。四种方法之间的肠球菌计数差异显著（P⩽0.05）。
