Gutierrez Alan, Xiong Zirui Ray, Johnson Shayla B, Brooks Ajani A, Gabriel Ellen, Adnan Adib, Vikram Amit, Callahan Mary Theresa, Sharma Manan
United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Environmental Microbial and Food Safety Laboratory, Beltsville, Maryland, USA.
United States Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Environmental Microbial and Food Safety Laboratory, Beltsville, Maryland, USA; University of Delaware, Department of Animal and Food Science, Newark, Delaware, USA.
J Food Prot. 2025 Aug 26;88(11):100605. doi: 10.1016/j.jfp.2025.100605.
Contaminated irrigation water in the preharvest environment can lead to outbreaks associated with fruits and vegetables. The potential of microbial contamination in preharvest waters by bacterial pathogens has created an ongoing demand for effective water treatment methods to mitigate this risk. This study sought to evaluate the efficacy of a commercial bacteriophage cocktail against Salmonella Infantis in agricultural water. A test agricultural water (TAW) medium prepared at different pH (6.5 and 8.4) and turbidity levels (4, 20, 50, and 100 NTU) was inoculated with a nalidixic acid resistant strain of S. Infantis (∼6 log CFU/mL), in triplicate trials, and treated with a bacteriophage cocktail (SalmoFresh™) at a phage titer of 8 log PFU/mL. Water samples were taken after a 5-minute contact time, with shaking (250 rpm), at 25 °C. Additionally, collected pond water, natural (nonsterile) and autoclaved, was inoculated with S. Infantis (∼4 log CFU/mL) and treated with bacteriophage cocktail (7 log PFU/mL or 8 log PFU/mL) at either 12 °C or 32 °C for 5, 10, or 30 min in triplicate trials. Samples were enumerated by plating onto XLD or TSA supplemented with 50 μg/mL Nalidixic acid. In TAW, S. Infantis levels were reduced by an average of 1.0 log CFU/mL after the 5-minute phage treatment, with no significant differences in reductions across all pH and turbidity levels tested (p > 0.05). In pond water (natural and autoclaved), S. Infantis reductions only occurred when the phage titer was 8 log PFU/mL, with average reductions of 1.04, 1.50, and 1.67 log CFU/mL after 5, 10, and 30 min, respectively, at 32 °C. At 12 °C, average reductions were 0.90, 1.15, and 1.36 log CFU/mL after 5, 10, and 30 min, respectively. These results demonstrate that commercial lytic phage cocktail specific for Salmonella are effective in water across various conditions (pH, turbidity, temperature) and may be considered with other technologies to reduce Salmonella levels in agricultural water.
收获前环境中受污染的灌溉水可导致与水果和蔬菜相关的疫情爆发。细菌病原体在收获前水域造成微生物污染的可能性使得人们一直需要有效的水处理方法来降低这种风险。本研究旨在评估一种商业噬菌体鸡尾酒对农业用水中婴儿沙门氏菌的功效。在不同pH值（6.5和8.4）和浊度水平（4、20、50和100 NTU）下制备的试验农业用水（TAW）培养基接种耐萘啶酸的婴儿沙门氏菌菌株（约6 log CFU/mL），进行三次重复试验，并用噬菌体效价为8 log PFU/mL的噬菌体鸡尾酒（SalmoFresh™）处理。在25°C下振荡（250 rpm）5分钟后采集水样。此外，将采集的池塘水（天然的和经过高压灭菌的）接种婴儿沙门氏菌（约4 log CFU/mL），并在12°C或32°C下用噬菌体鸡尾酒（7 log PFU/mL或8 log PFU/mL）处理5、10或30分钟，进行三次重复试验。通过接种到添加了50μg/mL萘啶酸的XLD或TSA平板上对样品进行计数。在TAW中，经过5分钟的噬菌体处理后，婴儿沙门氏菌水平平均降低了1.0 log CFU/mL，在所有测试的pH值和浊度水平下，降低幅度均无显著差异（p>0.05）。在池塘水（天然的和经过高压灭菌的）中，只有当噬菌体效价为8 log PFU/mL时，婴儿沙门氏菌数量才会减少，在32°C下，分别处理5、10和30分钟后，平均减少量分别为1.04、1.50和1.67 log CFU/mL。在12°C下，分别处理5、10和30分钟后，平均减少量分别为0.90、1.15和1.36 log CFU/mL。这些结果表明，针对沙门氏菌的商业裂解噬菌体鸡尾酒在各种条件（pH值、浊度、温度）的水中均有效，可与其他技术一起考虑用于降低农业用水中的沙门氏菌水平。
