Division of Food Processing Science and Technology, U. S. Food and Drug Administration, Bedford Park, IL, USA.
Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, IL, USA.
J Food Prot. 2024 Jun;87(6):100289. doi: 10.1016/j.jfp.2024.100289. Epub 2024 May 1.
Challenge studies associated with fruits and vegetables generally utilize wet bacterial inoculation methods. However, a recent salmonellosis outbreak in the U.S. was linked to peaches plausibly contaminated via fugitive dust from a nearby animal operation. This outbreak has highlighted the need for a suitable inert carrier which can be used for the dry transfer of Salmonella enterica to produce. The purpose of this study was 1) to examine the population stability of S. enterica and its surrogate, Enterococcus faecium, in different dry matrices during extended storage to identify suitable carriers and 2) to evaluate the survival of S. enterica on peaches based on the mode of contamination (i.e., wet vs. dry). S. enterica and E. faecium were cultivated on tryptic soy agar (TSA) and inoculated into corn-cob small animal litter, sand, or silica at 10-11 log CFU/g. Matrices were mixed by hand and stored at 25°C and 33% relative humidity for up to 120 d. S. enterica remained relatively stable in the silica and litter, with no significant decrease in population after 14 and 28 d, respectively. E. faecium significantly reduced in all matrices, with the greatest reduction observed in silica (2.86 log CFU/g after 120 d). Additional carriers would need to be assessed for E. faecium which could maintain its population stability. Silica was ultimately selected for the dry carrier of S. enterica. Peaches available at retail or from orchards were inoculated with S. enterica using the silica carrier or by spot or dip inoculation methods at 5 log CFU/peach and stored at 5°C and 80% relative humidity for up to 28 d. The population of S. enterica significantly reduced on all peaches except for the dry inoculated orchard peaches, where the population remained stable (4.62 ± 0.35 log CFU/peach after 28 d). Results from this study determined that the mode of contamination influences the survival of S. enterica on peaches and that dry inoculation methods should be considered for produce in some instances.
挑战研究与水果和蔬菜通常利用湿细菌接种方法。然而，最近在美国爆发的沙门氏菌病与桃子有关，这些桃子可能是附近动物养殖场的扬尘污染所致。此次疫情凸显了需要一种合适的惰性载体，可以用于干燥转移肠炎沙门氏菌，以生产。本研究的目的是：1）研究肠炎沙门氏菌及其替代菌粪肠球菌在不同干燥基质中的种群稳定性，以确定合适的载体；2）评估肠炎沙门氏菌在桃子上的存活情况，根据污染模式（即湿接种或干接种）。将肠炎沙门氏菌和粪肠球菌在胰蛋白酶大豆琼脂（TSA）上培养，并接种到玉米芯小动物垫料、沙子或硅砂中，接种量为 10-11 log CFU/g。基质通过手动混合，并在 25°C 和 33%相对湿度下储存长达 120 天。肠炎沙门氏菌在硅砂和垫料中相对稳定，分别在 14 和 28 天后，种群数量没有显著减少。粪肠球菌在所有基质中均显著减少，在硅砂中减少最多（120 天后减少 2.86 log CFU/g）。需要评估更多的载体来维持粪肠球菌的种群稳定性。硅砂最终被选为肠炎沙门氏菌的干燥载体。从零售店或果园购买的桃子用硅砂载体或通过点或浸蘸接种方法用肠炎沙门氏菌接种，接种量为 5 log CFU/个桃子，在 5°C 和 80%相对湿度下储存，最长可达 28 天。除了干燥接种的果园桃子外，所有桃子上的肠炎沙门氏菌数量均显著减少，在 28 天后，其种群数量保持稳定（4.62±0.35 log CFU/个桃子）。本研究结果表明，污染模式影响肠炎沙门氏菌在桃子上的存活，在某些情况下，应考虑采用干燥接种方法对农产品进行处理。
