te Giffel M C, Beumer R R
Departement Levensmiddelentechnologie en Voedingswetenschappen, Afdeling Levensmiddelenleer.
Tijdschr Diergeneeskd. 1998 Nov 1;123(21):628-32.
In order to determine the major contamination sources of milk with (psychrotrophic) Bacillus cereus, the incidence of vegetative cells and spores of B. cereus on dairy farms, at two dairy processing plants and in pasteurized milk in household refrigerators was investigated. On dairy farms the major contamination sources were soil and faeces. In winter, when the cows were housed, used bedding probably also participates in this contamination route. The udder will be contaminated, finally resulting in the presence of B. cereus in raw milk. The organism could be detected in 35% of the raw milk samples analyzed. During processing, an increase in the percentage of positive samples was observed. These results suggest that B. cereus can be introduced via sources other than raw milk; equipment may play an important role in this. Biochemical and molecular typing showed that selection of strains takes place in the milk production chain. It was demonstrated that some types were found in the raw milk, during processing and in the end products, indicating that raw milk is an important source of contamination. Other types could only be detected after the pasteurization step in the production process supporting the assumption that additional contamination occurs during processing. If stored under proper conditions, maximum storage temperature 7 degrees C, and consumed within the expiration date, the levels of B. cereus in pasteurized milk will, in general, not exceed 10(5) per ml and cause no problems for healthy adults.
为了确定蜡样芽孢杆菌（嗜冷菌）污染牛奶的主要来源，对奶牛场、两家乳制品加工厂以及家用冰箱中巴氏杀菌牛奶中的蜡样芽孢杆菌营养细胞和芽孢的发生率进行了调查。在奶牛场，主要污染源是土壤和粪便。在冬季，当奶牛圈养时，用过的垫料可能也参与了这一污染途径。乳房会受到污染，最终导致生牛奶中出现蜡样芽孢杆菌。在所分析的35%的生牛奶样本中能检测到该菌。在加工过程中，阳性样本的百分比有所增加。这些结果表明，蜡样芽孢杆菌可通过生牛奶以外的来源引入；设备可能在其中起重要作用。生化和分子分型表明，菌株在牛奶生产链中会发生选择。结果表明，在生牛奶、加工过程和最终产品中发现了一些类型，这表明生牛奶是重要的污染源。其他类型只能在生产过程中的巴氏杀菌步骤之后检测到，这支持了在加工过程中发生额外污染的假设。如果在适当条件下储存，最高储存温度为7摄氏度，并在保质期内食用，巴氏杀菌牛奶中的蜡样芽孢杆菌水平通常不会超过每毫升10(5)个，对健康成年人不会造成问题。
