Lab of Food Microbiology and Food Preservation, Department Food Safety and Food Quality, Faculty Bioscience Engineering, Ghent University, Coupure Links 653B-9000 Ghent, Belgium.
J Food Prot. 2015 Apr;78(4):652-60. doi: 10.4315/0362-028X.JFP-14-354.
The survival of Salmonella and Escherichia coli O157:H7 on strawberries, basil leaves, and other leafy greens (spinach leaves, lamb and butterhead lettuce leaves, baby leaves, and fresh-cut iceberg lettuce) was assessed at cold (<7 °C) and ambient temperatures. All commodities were spot inoculated with E. coli O157:H7 or Salmonella to obtain an initial inoculum of 5 to 6 log and 4 to 5 log CFU/g for strawberries and leafy greens, respectively. Samples were air packed. Strawberries were stored at 4, 10, 15, and 22 °C and basil leaves and other leafy greens at 7, 15, and 22 °C for up to 7 days (or less if spoiled before). Both Salmonella and E. coli O157:H7 showed a gradual decrease in numbers if inoculated on strawberries, with a similar reduction observed at 4, 10, and 15 °C (2 to 3 log after 5 days). However, at 15 °C (and 10 °C for E. coli O157:H7), the survival experiment stopped before day 7, as die-off of both pathogens below the lower limit of detection was achieved or spoilage occurred. At 22 °C, strawberries were moldy after 2 or 4 days. At that time, a 1- to 2-log reduction of both pathogens had occurred. A restricted die-off (on average 1.0 log) and increase (on average , 0.5 log) of both pathogens on basil leaves occurred after 7 days of storage at 7 and 22 °C, respectively. On leafy greens, a comparable decrease as on basil was observed after 3 days at 7 °C. At 22 °C, both pathogens increased to higher numbers on fresh-cut iceberg and butterhead lettuce leaves (on average 1.0 log), probably due to the presence of exudates. However, by using spot inoculation, the increase was rather limited, probably due to minimized contact between the inoculum and cell exudates. Avoiding contamination, in particular, at cultivation (and harvest or postharvest) is important, as both pathogens survive during storage, and strawberries, basil, and other leafy green leaves are consumed without inactivation treatment.
在冷藏（<7°C）和常温下，评估了草莓、罗勒叶和其他绿叶菜（菠菜叶、羊生菜和奶油生菜叶、婴儿叶和新鲜切块的生菜）上的沙门氏菌和大肠杆菌 O157:H7 的存活情况。所有商品均采用点接种法接种大肠杆菌 O157:H7 或沙门氏菌，使草莓和绿叶菜的初始接种量分别达到 5 到 6 对数和 4 到 5 对数 CFU/g。样品进行空气包装。草莓储存在 4、10、15 和 22°C，罗勒叶和其他绿叶菜储存在 7、15 和 22°C，最长可达 7 天（或更早变质）。如果接种在草莓上，无论是沙门氏菌还是大肠杆菌 O157:H7，其数量都会逐渐减少，在 4、10 和 15°C 观察到类似的减少（5 天后减少 2 到 3 对数）。然而，在 15°C（大肠杆菌 O157:H7 为 10°C），在第 7 天之前，由于病原体的死亡达到检测下限以下或变质发生，生存实验停止。在 22°C，草莓在 2 或 4 天后发霉。此时，两种病原体的数量减少了 1 到 2 对数。在 7 和 22°C 下分别储存 7 天后，罗勒叶上的两种病原体的死亡（平均 1.0 对数）和增加（平均 0.5 对数）受到限制。在 7°C 下储存 3 天后，绿叶菜上观察到与罗勒相似的减少。在 22°C，两种病原体在新鲜切块的生菜和奶油生菜叶上的数量增加到更高的水平（平均增加 1.0 对数），这可能是由于渗出物的存在。然而，通过采用点接种，增加量相当有限，这可能是由于接种物与细胞渗出物的接触最小化所致。避免污染，特别是在种植（和收获或收获后）期间，非常重要，因为两种病原体在储存期间都会存活，而且草莓、罗勒和其他绿叶菜在未经灭活处理的情况下被食用。
