食品标本处理方法对大肠埃希菌检出限影响

目的 研究快速、敏感、低成本的食品标本处理方法。方法 在牛肉馅中接种不同浓度的大肠埃希菌O157：H7，经离心、过滤，去除PCR抑制剂。浓缩菌株，用煮沸法和酶／冻融法裂解菌株，制备模板DNA。通过PCR检测大肠埃希菌O157：H7志贺毒素基因以评价该处理方法的可行性。结果 在未增菌条件下，PCR最低能检测到103CFU／g牛肉馅，增菌6h，最低能检测1CFU／g牛肉馅，整个检测过程只需要12h。结论 所采用的标本处理方法是一种灵敏、省时、低成本的方法，能显著地提高PCR检测食品标本中的大肠埃希菌O157：H7的灵敏度。

Sample preparation for PCR detection of Enterohaemorrhagic E.coli in food

Objective To develop a rapid,sensitive and cost-effective sample preparation for PCR detection of EHEC O157:H7 in ground beef.Methods Ground beef samples were inoculated with varying concentrations of E.coli O157:H7.PCR inhibitors were removed and bacterial cells were concentrated by filtration and centrifugation.DNA was purified and concentrated using enzymatic digestion and successive freeze/thaw cycles and the Shiga toxin gene was amplified using PCR to evaluate the sample preparation method.Results Without prior enrichment of cells in broth media,the detection limit was 10~3 CFU/g beef.When a 6 h enrichment step was incorporated,the detection limit was 1 CFU/g beef.The total time required from beginning to end of the procedure was 12 h.Conclusion The sample preparation method can substantially improved the sensitivity of E.coli O157:H7 by PCR detection.