Macarisin Dumitru, Wooten Anna, De Jesus Antonio, Hur Minji, Bae Seonjae, Patel Jitendra, Evans Peter, Brown Eric, Hammack Thomas, Chen Yi
Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, United States.
Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD 20740, United States.
Int J Food Microbiol. 2017 Sep 18;257:165-175. doi: 10.1016/j.ijfoodmicro.2017.06.018. Epub 2017 Jun 19.
Recent listeriosis outbreaks and recalls associated with cantaloupes urge for studies to understand the mechanisms of cantaloupe contamination by Listeria monocytogenes. Postharvest practices such as washing and hydrocooling were suggested to facilitate the contamination of fresh fruits by human pathogens. This study assessed the potential of L. monocytogenes internalization into cantaloupes during dump tank washing and immersion-type hydrocooling in water contaminated with L. monocytogenes. The effect of cantaloupe cultivar, water temperature, and harvesting technique on L. monocytogenes internalization was also evaluated. Full slip (cantaloupe without any residual stem) Western and Eastern cultivar cantaloupes were pre-warmed to 42°C (to imitate peak-high field temperatures of freshly harvested cantaloupes) and then immersed in water at 6°C and 18°C containing 4 and 6logCFU/ml of L. monocytogenes. Clipped (cantaloupe with short stem residues obtained by clipping the stem at harvest) Western and Eastern cantaloupes were pre-warmed to 42°C and then immersed in water at 6°C containing 6logCFU/ml of L. monocytogenes. Additionally, full slip and clipped Western cantaloupes were equilibrated to 18°C and then immersed in water at 18°C containing 6logCFU/ml of L. monocytogenes (isothermal immersion without temperature differential). Water containing L. monocytogenes infiltrated both full slip and clipped cantaloupes through the stems/stem scars and was then distributed along the vascular system in hypodermal mesocarp reaching the calyx area of the fruit. The current study demonstrated that, under experimental conditions, L. monocytogenes can internalize into cantaloupes during immersion in water contaminated by L. monocytogenes, both in the presence and absence of temperature differential, and that temperature differential moderately enhanced the internalization of L. monocytogenes. The incidence and levels of L. monocytogenes internalized in the middle-mesocarp were significantly affected by harvesting technique but not by cantaloupe cultivar.
近期与哈密瓜相关的李斯特菌病爆发及召回事件促使人们开展研究，以了解单核细胞增生李斯特菌污染哈密瓜的机制。有人提出，诸如清洗和水冷等采后处理措施会促使人类病原体污染新鲜水果。本研究评估了在倾卸槽清洗以及在被单核细胞增生李斯特菌污染的水中进行沉浸式水冷过程中，单核细胞增生李斯特菌侵入哈密瓜的可能性。还评估了哈密瓜品种、水温及采收技术对单核细胞增生李斯特菌侵入的影响。将全脱蒂（无任何残留茎部的哈密瓜）的西部和东部品种哈密瓜预热至42°C（以模拟刚采收的哈密瓜的峰值高温田间温度），然后浸入含有4和6logCFU/ml单核细胞增生李斯特菌的6°C和18°C水中。将带蒂（采收时通过剪茎获得带有短茎残留物的哈密瓜）的西部和东部哈密瓜预热至42°C，然后浸入含有6logCFU/ml单核细胞增生李斯特菌的6°C水中。此外，将全脱蒂和带蒂的西部哈密瓜平衡至18°C，然后浸入含有6logCFU/ml单核细胞增生李斯特菌的18°C水中（无温差的等温浸泡）。含有单核细胞增生李斯特菌的水通过茎部/茎痕渗入全脱蒂和带蒂的哈密瓜，然后沿皮下中果皮的维管系统分布，到达果实的花萼区域。当前研究表明，在实验条件下，单核细胞增生李斯特菌在浸入被其污染的水中时，无论有无温差，均可侵入哈密瓜，且温差会适度增强单核细胞增生李斯特菌的侵入。中果皮中侵入的单核细胞增生李斯特菌的发生率和水平受采收技术的显著影响，但不受哈密瓜品种的影响。
