Shaw Angela Laury, Svoboda Amanda, Jie Beatrice, Nonnecke Gail, Mendonca Aubrey
Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA.
Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA.
Food Microbiol. 2015 Apr;46:200-203. doi: 10.1016/j.fm.2014.06.027. Epub 2014 Jul 17.
Strawberries are soft fruit that are not recommended to have a post-harvest wash due to quality concerns. Escherichia coli O157:H7 has been linked to outbreaks with strawberries but little is known about the survival of E. coli during the growth cycle of strawberries. The survival of E. coli on strawberry plants during growing under greenhouses conditions was evaluated. Soil, leaves, and strawberries (if present) were artificially contaminated with an E. coli surrogate either at the time of planting, first runner removal (4 wk), second runner removal (8 wk), or one week prior to harvest. At harvest E. coli was recovered from the leaves, soil, and strawberries regardless of the contamination time. Time of contamination influenced (P < 0.05) numbers of viable E. coli on the plant. The highest survival of E. coli (P < 0.0001) was detected in soil that was contaminated at planting (4.27 log10 CFU g soil(-1)), whereas, the survival of E. coli was maximal at later contamination times (8 wk and 1 wk prior to harvest) for the leaves (4.40 and 4.68 log10 CFU g leaves(-1)) and strawberries (3.37 and 3.53 log10 CFU strawberry(-1)). Cross contamination from leaves to fruit was observed during this study, with the presence of E. coli on strawberries which had not been present at the time of contamination. These results indicate that good agricultural best practices to avoid contamination are necessary to minimize the risk of contamination of these popular fruit with enteric pathogens. Practices should include soil testing prior to harvest and avoiding contamination of the leaves.
草莓是软质水果，出于质量考虑，不建议进行采后清洗。大肠杆菌O157:H7与草莓引发的疫情有关，但人们对大肠杆菌在草莓生长周期中的存活情况知之甚少。本研究评估了温室条件下草莓植株上大肠杆菌的存活情况。在种植时、摘除首批匍匐茎时（4周）、摘除第二批匍匐茎时（8周）或收获前一周，用大肠杆菌替代物对土壤、叶片和草莓（如果有）进行人工污染。收获时，无论污染时间如何，均可从叶片、土壤和草莓中检出大肠杆菌。污染时间影响（P < 0.05）植株上大肠杆菌的存活数量。在种植时污染的土壤中检测到大肠杆菌的最高存活率（P < 0.0001）（4.27 log10 CFU g土壤-1），而对于叶片（4.40和4.68 log10 CFU g叶片-1）和草莓（3.37和3.53 log10 CFU草莓-1），大肠杆菌在后期污染时间（8周和收获前1周）的存活率最高。在本研究中观察到从叶片到果实的交叉污染，即污染时不存在大肠杆菌的草莓上出现了大肠杆菌。这些结果表明，为尽量降低这些常见水果被肠道病原体污染的风险，采取良好农业操作规范以避免污染是必要的。操作规范应包括收获前进行土壤检测以及避免叶片污染。
