Kim Hyochin, Bhunia Arun K
Department of Food Science, 745 Agriculture Mall Dr., Purdue University, West Lafayette, IN 47907-2009, USA.
Appl Environ Microbiol. 2008 Aug;74(15):4853-66. doi: 10.1128/AEM.02756-07. Epub 2008 Jun 6.
Multipathogen detection on a single-assay platform not only reduces the cost for testing but also provides data on the presence of pathogens in a single experiment. To achieve this detection, a multipathogen selective enrichment medium is essential to allow the concurrent growth of pathogens. SEL broth was formulated to allow the simultaneous growth of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes. The results were compared to those obtained with the respective individual selective enrichment broths, Rappaport-Vassiliadis (RV) for S. enterica, modified E. coli broth with 20 mg of novobiocin/liter for E. coli O157:H7, and Fraser broth for L. monocytogenes, and a currently used universal preenrichment broth (UPB). The growth of each pathogen in SEL inoculated at 10(1) or 10(3) CFU/ml was superior to that in the respective individual enrichment broth, except in the case of RV, in which Salmonella cells inoculated at both concentrations grew equally well. In mixed-culture experiments with cells of the three species present in equal concentrations or at a 1:10:1,000 ratio, the overall growth was proportional to the initial inoculation levels; however, the growth of L. monocytogenes was markedly suppressed when cells of this species were present at lower concentrations than those of the other two species. Further, SEL was able to resuscitate acid- and cold-stressed cells, and recovery was comparable to that in nonselective tryptic soy broth containing 6% yeast extract but superior to that in the respective individual selective broths. SEL promoted the growth of all three pathogens in a mixture in ready-to-eat salami and in turkey meat samples. Moreover, each pathogen was readily detected by a pathogen-specific immunochromatographic lateral-flow or multiplex PCR assay. Even though the growth of each pathogen in SEL was comparable to that in UPB, SEL inhibited greater numbers of nontarget organisms than did UPB. In summary, SEL was demonstrated to be a promising new multiplex selective enrichment broth for the detection of the three most prominent food-borne pathogens by antibody- or nucleic acid-based methods.
在单一检测平台上进行多病原体检测不仅能降低检测成本，还能在单个实验中提供病原体存在的数据。为实现这种检测，一种多病原体选择性富集培养基对于使病原体同时生长至关重要。SEL肉汤的配方旨在使肠炎沙门氏菌、大肠杆菌O157:H7和单核细胞增生李斯特菌同时生长。将结果与用各自单独的选择性富集肉汤（用于肠炎沙门氏菌的Rappaport-Vassiliadis（RV）肉汤、每升含20毫克新生霉素的改良大肠杆菌肉汤用于大肠杆菌O157:H7、用于单核细胞增生李斯特菌的Fraser肉汤）以及一种目前使用的通用预富集肉汤（UPB）所获得的结果进行比较。在接种浓度为10(1)或10(3) CFU/ml的SEL中，每种病原体的生长情况均优于各自单独的富集肉汤，但肠炎沙门氏菌在RV肉汤中的情况除外，在RV肉汤中，两种浓度接种的沙门氏菌细胞生长情况相同。在三种菌浓度相等或以1:10:1000比例存在的混合培养实验中，总体生长与初始接种水平成比例；然而，当单核细胞增生李斯特菌的细胞浓度低于其他两种菌时，其生长受到明显抑制。此外，SEL能够使酸应激和冷应激细胞复苏，复苏效果与含6%酵母提取物的非选择性胰蛋白胨大豆肉汤相当，但优于各自单独的选择性肉汤。SEL促进了即食香肠和火鸡肉样品中混合物中所有三种病原体的生长。此外，通过病原体特异性免疫层析侧向流动或多重PCR检测法可轻松检测到每种病原体。尽管每种病原体在SEL中的生长情况与在UPB中的相当，但SEL比UPB抑制了更多的非目标生物体。总之，SEL被证明是一种有前景的新型多重选择性富集肉汤，可通过基于抗体或核酸的方法检测三种最主要的食源性病原体。
