Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland.
Int J Food Microbiol. 2011 Jun 30;147(3):188-94. doi: 10.1016/j.ijfoodmicro.2011.04.001. Epub 2011 Apr 13.
The efficacy of bacteriophages e11/2 and e4/1c as potential biocontrol agents for Escherichia coli O157:H7 in food applications was assessed under conditions relevant to the food chain environment. The stability of each phage was determined following exposure to varying environmental conditions (pH, temperature, water activity, and sodium chloride) and the ability of each phage to infect and reduce E. coli O157:H7 numbers under selected conditions was also examined. Both e11/2 and e4/1c significantly (p<0.05) reduced numbers of E. coli O157:H7 when exposed to pH values ranging from pH>4 to pH 9, temperatures from 4 °C to 37 °C, water activity values of 0.87 or 0.91 to 1.00 and NaCl concentrations of 1% to 2.5%. Subsequently, a cocktail of both phages was used (e11/2 and e4/1c) to assess reduction of E. coli O157:H7 on cattle hide pieces. This involved inoculating pieces of hide (20×20 cm) with E. coli O157:H7 (approximately 10⁶cfu/cm²) which were subsequently treated with either a suspension of a phage cocktail, consisting of e11/2 and e4/1c (multiplicity of infection of 1000 and 10,000, respectively) or water or not treated. Two different investigations were carried out; immediately or 1h after treatment application was performed in different experiments. Swab samples taken immediately after phage treatment showed no significant (p>0.05) reduction of E. coli O157:H7 numbers compared to the water treated or untreated samples. However, an extended exposure time of 1h following phage application revealed a significant reduction (p<0.05) (1.5 log₁₀ cfu/cm² reduction) in E. coli O157:H7 numbers compared to the numbers recovered on samples treated with water only. These findings demonstrate the potential use of e11/2 and e4/1c phages as a biocontrol agent for E. coli O157:H7 within various stages of the food chain, including on cattle hide.
评估了噬菌体 e11/2 和 e4/1c 作为食品应用中大肠杆菌 O157:H7 的潜在生物防治剂的功效，这些噬菌体的稳定性是在与食物链环境相关的各种环境条件（pH 值、温度、水活度和氯化钠）下确定的，并且还研究了每种噬菌体在选定条件下感染和减少大肠杆菌 O157:H7 数量的能力。当暴露于 pH 值范围从 pH>4 到 pH 9、温度范围从 4°C 到 37°C、水活度值为 0.87 或 0.91 到 1.00 和 NaCl 浓度为 1%到 2.5%时，e11/2 和 e4/1c 都显著（p<0.05）降低了大肠杆菌 O157:H7 的数量。随后，使用噬菌体鸡尾酒（e11/2 和 e4/1c）来评估牛皮片上大肠杆菌 O157:H7 的减少情况。这涉及用大肠杆菌 O157:H7（约 10⁶cfu/cm²）接种牛皮片（20×20cm），然后用噬菌体鸡尾酒的悬浮液（感染复数分别为 1000 和 10000）或水或不处理。进行了两次不同的研究；在不同的实验中，立即或在处理后 1 小时进行处理应用。与水或未处理的样品相比，在噬菌体处理后立即采集的拭子样品中，大肠杆菌 O157:H7 的数量没有显著（p>0.05）减少。然而，噬菌体应用后延长 1 小时的暴露时间显示大肠杆菌 O157:H7 数量有显著减少（p<0.05）（1.5log₁₀cfu/cm²减少），与仅用水处理的样品上回收的数量相比。这些发现表明 e11/2 和 e4/1c 噬菌体可作为大肠杆菌 O157:H7 的生物防治剂在食物链的各个阶段使用，包括牛皮。
