Arocha Marlene M, McVey Melinda, Loder Susan D, Rupnow John H, Bullerman Lloyd
Centro de Investigaciones, Facultad de Farmacia, Universidad Santa Maria, Av. Paez El Paraiso, Caracas, Venezuela.
Department of Food Science and Technology, University of Nebraska, 143 Filley Hall, Lincoln, Nebraska 68583-0919.
J Food Prot. 1992 May;55(5):379-381. doi: 10.4315/0362-028X-55.5.379.
The ability of enterohemorrhagic Escherichia coli O157:H7 to grow and survive during the manufacture of Cottage cheese was determined. Pasteurized skim milk artificially contaminated with E. coli O157:H7 was used to make Cottage cheese by the washed curd method. E. coli O157:H7 was enumerated by surface plating samples on MacConkey sorbitol agar with 5-bromo-4-chloro-3-indoxyl-β-D-glucuronic acid cyclohexylammonium salt (MSA-BCIG) and incubating at 42°C for 24 h. The heat treated samples were previously inoculated into a modified EC broth with novobiocin and incubated static at 35°C for 24 h. Sorbitol and β-glucuronidase negative colonies were picked from MSA-BCIG, spread on Levine eosin methylene blue agar plates and phenol red sorbitol agar plates with 4-methylumbelliferyl-β-D-glucuronide (PRS-MUG) added for confirmation. E. coli O157:H7 increased 100-fold in numbers during the manufacturing process, but death occurred during cooking of the curd and whey. The pH and acidity did not halt the growth of this pathogen during the manufacture of the cheese; furthermore, the values of these parameters were the same between the contaminated and control samples.
测定了肠出血性大肠杆菌O157:H7在农家干酪制作过程中的生长和存活能力。用人工感染O157:H7大肠杆菌的巴氏杀菌脱脂乳，通过洗凝乳法制作农家干酪。通过将样品表面接种于含5-溴-4-氯-3-吲哚基-β-D-葡糖醛酸环己铵盐的麦康凯山梨醇琼脂（MSA-BCIG）上，并在42°C孵育24小时来计数O157:H7大肠杆菌。将热处理后的样品预先接种到含新生霉素的改良EC肉汤中，在35°C静态孵育24小时。从MSA-BCIG上挑取山梨醇和β-葡糖醛酸酶阴性菌落，涂布于添加了4-甲基伞形酮基-β-D-葡糖醛酸（PRS-MUG）的莱文伊红美蓝琼脂平板和酚红山梨醇琼脂平板上进行确证。在制作过程中，O157:H7大肠杆菌数量增加了100倍，但在凝乳和乳清烹饪过程中出现死亡。在奶酪制作过程中，pH值和酸度并未阻止这种病原体的生长；此外，污染样品和对照样品之间这些参数的值相同。
