Tomatoes have been linked to Salmonella outbreaks in the United States (US). Plasticulture systems, that combine raised beds, plastic mulch, drip irrigation and fumigation, are common in commercial staked fresh tomato production in the US. The US FDA Produce Safety Rule prohibits the distribution of any produce covered by the rule (including fresh market tomatoes) that drops to the ground before harvest. This research was undertaken to better characterize the risks posed by tomatoes that touch plastic mulch or soil immediately before or during harvest. Research was conducted in three states (Florida, Maryland, and Ohio). Each state utilized tomatoes from their state at the point of harvest maturity most common in that state. Each state used indigenous soil and plastic mulch for transfer scenarios. New plastic mulch obtained directly from the application roll and used plastic mulch that had been present on beds for a growing season were evaluated. A five-strain cocktail of Salmonella enterica isolates obtained from tomato outbreaks was used. Mulch (new or used), soil, or tomatoes were spot inoculated with 100 μl of inoculum to obtain a final population of ~6 log CFU/surface. Items were either touched to each other immediately (1-2 s) after inoculation (wet contact) or allowed to dry at ambient temperature for 1 h or 24 h (dry contact). All surfaces remained in brief (1-5 s) or extended (24 h) contact at ambient temperature. Transfer of Salmonella between a tomato and plastic mulch or soil is dependent on contact time, dryness of the inoculum, type of soil, and contact surface. Transfer of Salmonella to and from the mulch and tomatoes for wet and 1 h dry inocula were similar with mean log % transfers varying from 0.7 ± 0.2 to 1.9 ± 0.1. The transfer of Salmonella between soil or plastic mulch to and from tomatoes was dependent on moisture with wet and 1 h dry inocula generally yielding significantly (p < 0.05) higher transfer than the 24 h dry inoculum. Results indicate that harvesting dry tomatoes significantly (p < 0.05) reduces the risk of contamination from soil or mulch contact. Transfer to tomatoes was generally significantly greater (p < 0.05) from new and used plastic mulch than from soil. If contamination and moisture levels are equivalent and contact times are equal to or <24 h before harvest, significantly (p < 0.05) more Salmonella transfers to tomatoes from mulch than from soil. Our findings support that harvesting tomatoes from soil has similar or lower risk than harvesting from plastic mulch.

中文翻译：

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定量沙门氏菌在番茄，土壤和塑料覆盖物之间的转移。

在美国，西红柿与沙门氏菌的爆发有关。结合了高架床，塑料覆盖物，滴灌和熏蒸的塑化系统在美国商业化的新鲜番茄生产中很常见。美国FDA的《农产品安全法规》禁止该法规涵盖的任何农产品（包括新鲜市场番茄）的分发，这些农产品在收获前掉到地面上。进行这项研究的目的是为了更好地表征番茄在收获前或收获期间接触塑料覆盖物或土壤的风险。在三个州（佛罗里达州，马里兰州和俄亥俄州）进行了研究。每个州都在该州最常见的收获成熟点利用番茄。每个州都使用本地土壤和塑料覆盖物进行转移。评估了直接从施肥辊上获得的新塑料覆盖物，以及已经在床上生长了一个季节的用过的塑料覆盖物。使用从番茄暴发中获得的五株肠炎沙门氏菌混合物。将覆盖物（新的或二手的），土壤或西红柿用100μl接种物进行点接种，以获得最终种群〜6 log CFU /表面。接种后立即（1-2秒钟）使物品彼此接触（湿接触），或者在环境温度下使其干燥1小时或24小时（干接触）。在环境温度下，所有表面都保持短暂接触（1-5秒）或长时间接触（24小时）。沙门氏菌在番茄和塑料覆盖物或土壤之间的转移取决于接触时间，接种物的干燥度，土壤类型和接触表面。湿和1小时干接种物中沙门氏菌与覆盖物和番茄之间的转移相似，平均对数百分比转移范围从0.7±0.2到1.9±0.1。沙门氏菌在土壤或塑料覆盖物之间与西红柿之间的转移取决于水分，湿的和1小时的干接种通常比24小时的干接种显着提高（p <0.05）。结果表明，收获干燥番茄可显着降低（p <0.05）污染土壤或覆盖物的风险。通常，新的和使用过的塑料覆盖物向番茄的转移比从土壤的转移显着更大（p <0.05）。如果污染和水分含量相等，并且收获前的接触时间等于或小于24小时，则从覆盖物向番茄的沙门氏菌转移比从土壤中转移的沙门氏菌多得多（p <0.05）。