Environmental Microbial and Food Safety Laboratory, USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD, 20705, USA.
Environmental Microbial and Food Safety Laboratory, USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD, 20705, USA.
Food Microbiol. 2021 May;95:103677. doi: 10.1016/j.fm.2020.103677. Epub 2020 Nov 10.
Imported papayas from Mexico have been implicated in multiple salmonellosis outbreaks in the United States in recent years. While postharvest washing is a critical process to remove latex, dirt, and microbes, it also has the potential of causing cross-contamination by foodborne pathogens, with sponge or other fibrous rubbing tools often questioned as potential harboring or transmitting risk. In this study, Salmonella inactivation and cross-contamination via sponges and microfiber wash mitts during simulated papaya washing and cleaning were investigated. Seven washing treatments (wash without sanitizer; wash at free chlorine 25, 50, and 100 mg/L, and at peracetic acid 20, 40, and 80 mg/L), along with unwashed control, were evaluated, using Salmonella strains with unique antibiotic markers differentially inoculated on papaya rind (serovars Typhimurium, Heidelberg, and Derby) and on wash sponge or microfiber (serovars Typhimurium, Newport, and Braenderup). Salmonella survival and transfer on papaya and on sponge/microfiber, and in wash water were detected using selective plating or enrichment. The washing and cleaning process reduced Salmonella on inoculated papayas by 1.69-2.66 and 0.69-1.74 log for sponge and microfiber cleaning, respectively, with the reduction poorly correlated to sanitizer concentration. Salmonella on inoculated sponge or microfiber was under detection limit (1.00 log CFU/cm) by plate count, but remained recoverable by selective enrichment. Transference of Salmonella from inoculated papaya to sponge/microfiber, and vice versa, could be detected sporadically by selective enrichment. Sponge/microfiber mediated Salmonella cross-contamination from inoculated to uninoculated papayas was frequently detectable by selective enrichment, but rendered undetectable by wetting sponge/microfiber in sanitizing wash water (FC 25-100 mg/L or PAA 20-80 mg/L) between washing different papaya fruits. Therefore, maintaining adequate sanitizer levels and frequently wetting sponge/microfiber in sanitizing wash water can effectively mitigate risks of Salmonella cross-contamination associated with postharvest washing, especially with regard to the use of sponge or microfiber wash mitts.
近年来，来自墨西哥的进口木瓜多次引发美国的沙门氏菌病疫情。尽管采后清洗是去除乳胶、污垢和微生物的关键过程，但它也有可能导致食源性病原体的交叉污染，而海绵或其他纤维擦手工具经常被质疑是潜在的携带或传播风险的来源。在这项研究中，研究了模拟木瓜清洗和清洁过程中通过海绵和微纤维洗涤手套对沙门氏菌的灭活和交叉污染。使用具有独特抗生素标记的沙门氏菌菌株，对木瓜果皮（血清型肠炎、海德堡和德尔比）和洗涤海绵或微纤维（血清型肠炎、纽波特和布伦德拉普）进行了七种不同的清洗处理（不用消毒剂清洗；用游离氯 25、50 和 100mg/L 以及过氧乙酸 20、40 和 80mg/L 清洗），以及未清洗的对照。使用选择性平板或增菌检测来检测木瓜和海绵/微纤维上的沙门氏菌存活和转移，以及洗涤水中的沙门氏菌存活和转移。清洗和清洁过程分别减少了接种木瓜上的沙门氏菌 1.69-2.66 和 0.69-1.74 个对数，而海绵和微纤维清洁的减少与消毒剂浓度相关性较差。接种海绵或微纤维上的沙门氏菌通过平板计数低于检测限（1.00 log CFU/cm），但通过选择性增菌仍可回收。通过选择性增菌可以偶尔检测到从接种木瓜到海绵/微纤维以及反之的沙门氏菌转移。通过选择性增菌经常可以检测到海绵/微纤维介导的从接种木瓜到未接种木瓜的沙门氏菌交叉污染，但在不同木瓜果实之间用含消毒剂的洗涤水（FC 25-100mg/L 或 PAA 20-80mg/L）润湿海绵/微纤维时可使其变得不可检测。因此，保持足够的消毒剂水平并经常在含消毒剂的洗涤水中润湿海绵/微纤维，可以有效降低与采后清洗相关的沙门氏菌交叉污染风险，特别是在使用海绵或微纤维洗涤手套的情况下。
