Quantitative analysis on the growth, migration, and attachment of Salmonella spp. during the alfalfa seed sprouting process.

摘要

Raw seed sprouts have been implicated in several food poisoning outbreaks in the last 10 years. Salmonella have been shown to be present on seed responsible for foodborne outbreaks. Research has shown that Salmonella multiply rapidly during the sprouting process, associate with sprouts and can be found in water used to irrigate sprouting seeds. Basic research has also shown that bacterial attachment in general is correlated with various factors, such as motility, lipo-polysaccharide (LPS), and exo-polysacchride (EPS). To better understand and model the risk of food poisoning linked to sprouts, a quantitative analysis of the growth, migration and attachment of Salmonella serotypes Stanley and Typhimurium was conducted during alfalfa seed sprouting.; No statistically significant differences were observed in microbial growth in two different types of sprouting environments (small flasks or a large bench-scale sprouting chamber). Microbial concentrations in irrigation water showed no statistically significant difference from samples taken at the same time from sprouts. Growth rates were also constant irrespective of inoculum level or strain, except that smaller inoculum levels reached lower final levels proportional to their initial levels. Moreover, a non-pathogenic, easy to isolate surrogate (Nalidixic acid resistant Enterobacter aerogenes ) gave similar results to those obtained with S. Stanley, supporting its use in future, production scale experiments. A model was developed which predicts microbial concentration as a function of time and distance from the initial site of contamination, or by detection on sprouts or in irrigation water during the sprouting process. This research has also shown that alfalfa sprouts held at room temperature do not support a significant growth of Salmonella, although it does, however, cause overt spoilage and significant quality losses in sprouts.; Our results also indicate that previously published Salmonella attachment assays on sprouts do not match the attachment actually observed during the sprouting process, and may not provide reliable results. Finally, our research provides evidence that the presence of flagella and the ability to synthesize cellulose appear to play an important role in Salmonella attachment to sprouts during the sprouting process.