Department of Food Science and Technology, University of Tennessee, Knoxville, Tennessee 37996-4591, USA.
Foodborne Pathog Dis. 2011 Apr;8(4):527-34. doi: 10.1089/fpd.2010.0721. Epub 2011 Mar 7.
Eggs and egg products have a high risk of Salmonella enterica serovar Enteritidis contamination leading to gastroenteritis outbreaks in humans. Thus, a rapid screening tool for viable Salmonella Enteritidis cells in the egg industry is needed. Our objective was to rapidly and sensitively detect viable Salmonella Enteritidis from spiked liquid whole eggs (LWEs) within 24 h using SYBR green I-based real-time reverse transcriptase-polymerase chain reaction (PCR) targeting the Salmonella specific invA gene along with an internal amplification control in a Bio-Rad iCycler. LWE was inoculated with Salmonella Enteritidis and mixed with tetrathionate broth, and 100 μL of serially diluted portions in phosphate-buffered saline was plated on Xylose Lysine Tergitol 4 agar or 5 mL were used for RNA extraction by the TRIzol method immediately or after enrichment of 6, 12, or 16 h at 37 °C. The real-time reverse transcriptase-PCR assay was carried out using previously described Salmonella invA gene primers. Melt temperature analysis of the PCR product was included to determine specific invA amplification. Without enrichment, the assay detection limit was 10(7) colony forming units (CFU)/25 mL LWE. After enrichment for 6 and 12 h, Salmonella Enteritidis could be detected from LWE up to 10(4) and 10(2) CFU/25 mL, respectively. Improved Salmonella Enteritidis detection up to 10(0) CFU/25 mL was obtained after 16-h enrichment. Even with 16-h enrichment, the results could be still be obtained within 24 h, which is much faster than by traditional cultural detection that takes several days. Therefore, this assay appears suitable for routine detection of Salmonella enterica contamination by the egg industry to help prevent the transmission of egg-associated Salmonella outbreaks and timely recall of contaminated products.
鸡蛋及其制品中含有大量的肠炎沙门氏菌血清型肠炎亚种,容易引发人类肠胃炎爆发。因此,需要一种能够快速检测鸡蛋制品中沙门氏菌的方法。本研究的目的是通过 SYBR Green I 实时荧光定量 RT-PCR 法检测食品中沙门氏菌。该方法针对沙门氏菌 invA 基因设计特异性引物,并通过内参基因校正,在 Bio-Rad iCycler 上 24 小时内对 10 倍稀释的液全蛋中添加的肠炎沙门氏菌进行检测,灵敏度为 107 CFU/25mL。样品经过增菌后,6、12、16 小时后,通过平板计数法或直接提取 RNA 后用实时荧光定量 RT-PCR 检测。未增菌时,检测限为 107 CFU/25mL。6 小时和 12 小时增菌后,该方法可分别检测到 104 和 102 CFU/25mL 的肠炎沙门氏菌。16 小时增菌后,检测限可达 100 CFU/25mL。即使经过 16 小时增菌,也能在 24 小时内得到结果,比传统的培养法快得多。因此,该方法适用于鸡蛋行业对沙门氏菌污染的常规检测,有助于防止鸡蛋相关沙门氏菌爆发和及时召回污染产品。