Kase Julie A, Maounounen-Laasri Anna, Lin Andrew
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Microbiology, College Park, Maryland 20740.
Oak Ridge Research Institute for Science and Education, Oak Ridge, Tennessee 37830.
J Food Prot. 2016 Sep;79(9):1623-1629. doi: 10.4315/0362-028X.JFP-16-070.
The U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) Chapter 4a describes a Luminex microbead-based suspension array used to screen colonies for 11 clinically relevant Shiga toxin-producing Escherichia coli (STEC) serogroups: O26, O45, O91, O103, O104, O111, O113, O121, O128, O145, and O157. We evaluated the usefulness of this method to identify STEC-positive enrichment samples before agar plating. Twelve E. coli strains were added to three types of fresh produce (bagged baby spinach, alfalfa sprouts, and cilantro) at levels near the detection limit of the test. A subset of these strains (six O serogroups) was similarly evaluated in raw milk. For comparison, portions of each of the 168 enrichment cultures were analyzed for serogroup by a real-time PCR assay and a Bio-Plex 200 assay with the bead-based suspensions. No false-positive results were obtained. Of the 112 samples with a reported cycle threshold (C) value, 101 undiluted, diluted, or extracted enrichment cultures also produced ratios above 5.0 in the Bio-Plex assay. When PCR C values approached or were greater than 35, Bio-Plex detection became less reliable. Using undiluted or extracted enrichment cultures resulted in a significantly larger number of positive results. With the same enrichment material prepared for real-time PCR analysis as described in the BAM Chapter 4a, the STEC microbead-based suspension array can accurately screen food enrichment cultures.
美国食品药品监督管理局的《细菌学分析手册》（BAM）第4a章介绍了一种基于Luminex微珠的悬浮阵列，用于筛查11种临床相关的产志贺毒素大肠杆菌（STEC）血清型菌落：O26、O45、O91、O103、O104、O111、O113、O121、O128、O145和O157。我们评估了该方法在琼脂平板接种前鉴定STEC阳性富集样品的实用性。将12株大肠杆菌以接近检测限的水平添加到三种新鲜农产品（袋装嫩菠菜、苜蓿芽和香菜）中。这些菌株的一个子集（6种O血清型）也在原料奶中进行了类似评估。为作比较，通过实时PCR检测和基于微珠悬浮液的Bio-Plex 200检测对168份富集培养物中的每一份进行血清型分析。未获得假阳性结果。在报告了循环阈值（C）值的112个样品中，101份未稀释、稀释或提取的富集培养物在Bio-Plex检测中的比率也高于5.0。当PCR C值接近或大于35时，Bio-Plex检测变得不太可靠。使用未稀释或提取的富集培养物可得到显著更多的阳性结果。使用与BAM第4a章所述相同的富集材料进行实时PCR分析，基于STEC微珠的悬浮阵列能够准确筛查食品富集培养物。
