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Bagged salads may promote growth of Salmonella

November 23, 2016: From IFT and Applied and Environmental Microbiology:

"A study published in Applied and Environmental Microbiology shows that small amounts of damage to salad leaves in bagged salads may encourage the presence of Salmonella enterica. Juices released from damaged leaves may also enhance the pathogen’s ability to attach to the salad’s plastic container. "
"In the study, salad juices in water—to mimic the grocery salad bag environment—more than doubled motility, or movement of individual Salmonella bacteria, supporting salad leaf colonization. In the course of a typical five-day refrigeration storage time, around 100 Salmonella bacteria multiplied to approximately 100,000 individual bacteria. Salad juices also boosted formation of biofilms on salad leaves. The researchers found that surprisingly, the normal microbial flora on salad leaves did not respond to leaf juices, suggesting that the leaf juices give Salmonella a marked advantage in colonizing salad leaves as compared to competing bacteria."
"The researchers concluded that “even very dilute levels of salad juices are potent stimulators of Salmonella growth and salad leaf attachment and colonization, and that the presence of the existing leaf microbiota does not prevent pathogen attachment. Salad juice exposure also has the potential to enhance Salmonella virulence, which may contribute to the severity of the food infections obtained from salad leaves."