Institute of Food Biotechnology, College of Food Science, South China Agricultural University, Guangzhou, Guangdong 510640, People's Republic of China.
Hygiena Singapore Pte Ltd., 80 Robinson Road #02-00, Singapore 068898.
J Food Prot. 2020 Mar 1;83(3):397-404. doi: 10.4315/0362-028X.JFP-19-280.
The BAX system for pathogen detection has been highly accurate in a variety of food products. However, false-negative results have been reported for the detection of pathogens in liquid egg products because of failed pathogen resuscitation and the existence of inhibitory components. In this study, a short-time enrichment step was used to simultaneously resuscitate the target cells to the detection level and to dilute the inhibitory components to reduce detection interference. The MP medium (BAX system) enabled faster multiplication of healthy Salmonella cells than did buffered peptone water (BPW) in tested liquid whole egg and egg yolk. However, MP failed to resuscitate heat-injured cells even after 24 h of incubation. Therefore, MP was replaced with BPW as the enrichment broth for the BAX system. However, the use of BPW for a one-step enrichment was not effective for removal of PCR inhibitors in egg yolk, and unstable detection results were obtained. To improve detection accuracy, a second step of enrichment with brain heart infusion was added. This two-step enrichment process shortened the enrichment time to 14 h and greatly increased the number of samples in which the pathogen was detected during the same enrichment time, especially in the liquid egg yolk samples. The validation study revealed 100% diagnostic accuracy of the two-step enrichment process plus the BAX system. These results indicate that a two-step enrichment process added to the BAX system can improve the detection of pathogenic Salmonella in liquid egg products.
BAX 病原体检测系统在多种食品中具有高度准确性。然而，由于病原体复苏失败和存在抑制成分，该系统在检测液体蛋制品中的病原体时会出现假阴性结果。在本研究中，采用短时间的富集步骤，同时将目标细胞复苏到检测水平，并稀释抑制成分，以减少检测干扰。在测试的液体全蛋和蛋黄中，MP 培养基（BAX 系统）比缓冲蛋白胨水（BPW）更能促进健康沙门氏菌细胞的增殖。然而，即使孵育 24 小时，MP 也未能复苏受热损伤的细胞。因此，BPW 被用作 BAX 系统的富集肉汤来替代 MP。然而，BPW 作为一步富集法并不能有效去除蛋黄中的 PCR 抑制剂，并且得到的检测结果不稳定。为了提高检测准确性，添加了脑心浸液的第二步富集。两步富集过程将富集时间缩短至 14 小时，并大大增加了在相同富集时间内检测到病原体的样本数量，特别是在液体蛋黄样本中。验证研究表明，两步富集加 BAX 系统的方法具有 100%的诊断准确性。这些结果表明，BAX 系统中添加两步富集过程可以提高液体蛋制品中致病性沙门氏菌的检测能力。
