U.S. Food and Drug Administration, Pacific Regional Laboratory Northwest, 23rd Drive S.E., Bothell, Washington 98021, USA.
J Food Prot. 2005 Aug;68(8):1593-9. doi: 10.4315/0362-028x-68.8.1593.
A new procedure for enrichment of Escherichia coli O157:H7 and other Shiga toxin-producing E. coli was compared to five standard methods: the British Public Health Laboratory Service, International Standard Method, U.S. Department of Agriculture, Canadian Health Products and Food Branch, and U.S. Food and Drug Administration. The new procedure was comparable to the standard methods in its ability to detect target cells inoculated into foods at approximately 1 CFU g(-1). Comparisons were also made of the ability of the six enrichment procedures to detect E. coli O157:H7 against a large background of competitor microorganisms. In these experiments the new procedure yielded more target cells than the other five enrichments by two to three orders of magnitude as determined by enumeration on sorbitol MacConkey agar with tellurite and cefixime and Rainbow agar with tellurite and novobiocin and by verification of presumptive colonies by real-time PCR. For example, the population of enterohemorrhagic E. coli strain 6341 recovered on sorbitol MacConkey agar with tellurite and cefixime after enrichment with the experimental method was 2.42 x 10(8) CFU ml(-1) and 1.80 x 10(6) CFU ml(-1) after enrichment with the Canadian Health Products and Food Branch method, the second most effective in this experiment. In addition, broth cultures resulting from each of the six enrichment procedures were used to prepare templates for real-time PCR detection of stx1/stx2. Resulting threshold cycle (Ct) values after the experimental enrichment were similar to positive control values, whereas the five standard methods produced delayed Ct values or were not detected.
一种新的富集大肠杆菌 O157:H7 和其他产志贺毒素大肠杆菌的方法与五种标准方法进行了比较：英国公共卫生实验室服务处、国际标准方法、美国农业部、加拿大卫生产品和食品处以及美国食品和药物管理局。该新方法在检测接种到食品中的目标细胞（约 1 CFU g(-1)）的能力方面与标准方法相当。还比较了六种富集方法在大量竞争微生物背景下检测大肠杆菌 O157:H7 的能力。在这些实验中，新方法通过在含有碲酸盐和头孢克肟的山梨醇麦康凯琼脂以及含有碲酸盐和新生霉素的彩虹琼脂上计数和通过实时 PCR 验证推定菌落，比其他五种富集方法多检测到两到三个数量级的目标细胞。例如，在用实验方法富集后，在含有碲酸盐和头孢克肟的山梨醇麦康凯琼脂上回收的肠出血性大肠杆菌菌株 6341 的种群为 2.42 x 10(8) CFU ml(-1)，而在用加拿大卫生产品和食品处方法（本实验中第二有效的方法）富集后的种群为 1.80 x 10(6) CFU ml(-1)。此外，还使用这六种富集方法中的每一种的肉汤培养物来制备用于实时 PCR 检测 stx1/stx2 的模板。实验富集后的结果循环阈值 (Ct) 值与阳性对照值相似，而五种标准方法产生延迟的 Ct 值或未检测到。
