Krascsenicsová Klára, Kaclíková Eva, Kuchta Tomás
Department of Microbiology and Molecular Biology, Food Research Institute, Bratislava, Slovakia.
New Microbiol. 2006 Oct;29(4):261-7.
Growth of Salmonella enterica was studied in model mixed cultures with Citrobacter freundii or Escherichia coli in buffered peptone water (BPW) and in Rappaport-Vassiliadis medium with soya (RVS) with modified concentrations of MgCl2 and malachite green, and at modified incubation temperatures. Selected S. enterica strains were inoculated in BPW (10(0) cfu/ml) together with selected strains of Citrobacter freundii (up to 10(8) cfu/ml) or selected strains of Escherichia coli (up to 10(8) cfu/ml), incubated overnight and then subcultured (1: 100) in RVS variants. Growth of individual bacterial species was followed by the quantitative real-time polymerase chain reaction (PCR). Optimal culture conditions during the second selective step were: MgCl2.6 H2O concentration of 29 g/l, malachite green concentration of 36 mg/1l, and the incubation temperature of 41.5 degrees C. Citr. freundii was found to be a potent competitor and E. coli was a weaker competitor. At optimal culture conditions, competition was reduced and the density of S. enterica cultures reached the level of 10(4) cfu/ml after not later than 2 h of selective enrichment. The results obtained provide a basis for the development of a short two-step enrichment to be used in rapid real-time PCR-based methods for the detection of S. enterica in food and other matrices.
在含有弗氏柠檬酸杆菌或大肠杆菌的模型混合培养物中，于缓冲蛋白胨水（BPW）以及含有不同浓度氯化镁和孔雀石绿的改良拉帕波特 - 瓦西里亚迪斯大豆培养基（RVS）中，在不同培养温度下研究了肠炎沙门氏菌的生长情况。将选定的肠炎沙门氏菌菌株接种于BPW（10⁰ cfu/ml）中，并与选定的弗氏柠檬酸杆菌菌株（最高达10⁸ cfu/ml）或选定的大肠杆菌菌株（最高达10⁸ cfu/ml）共同培养，过夜培养后再以1:100的比例转接至不同变体的RVS中。通过定量实时聚合酶链反应（PCR）跟踪各细菌种类的生长情况。第二步选择性培养的最佳条件为：MgCl₂·6H₂O浓度为29 g/l，孔雀石绿浓度为36 mg/1l，培养温度为41.5℃。结果发现弗氏柠檬酸杆菌是一种强大的竞争者，而大肠杆菌是较弱的竞争者。在最佳培养条件下，竞争减弱，肠炎沙门氏菌培养物的密度在不超过2小时的选择性富集后达到10⁴ cfu/ml的水平。所获得的结果为开发一种用于基于实时PCR快速检测食品及其他基质中肠炎沙门氏菌的短两步富集方法提供了依据。
