Project examines E. coli’s viability during romaine post-harvest cooling

Teresa Bergholz and Jade Mitchell, each Ph.D.’s with Michigan State College (MSU), hope to characterize the modifications that E. coli O157:H7 goes by on romaine lettuce throughout post-harvest chilly storage.

Their venture is titled “Quantifying danger related to modifications in EHEC physiology throughout post-harvest pre-processing phases of leafy inexperienced manufacturing.”

Their purpose is to develop an simply accessible on-line software that business can use to determine practices that cut back the dangers of E. coli O157:H7 transmission by way of romaine lettuce.

“Perhaps there’s one thing you are able to do to switch the best way you’re harvesting and cooling that permits you to cut back danger,” Bergholz stated. “Can we shift the harvest time and the way shortly we get it to the cooling heart?”

The Heart for Produce Security has awarded greater than $300,000 to fund this analysis venture.

In comparison with the rising season and processing, the time romaine spends in coolers and refrigerated transport after harvest isn’t very lengthy. Nonetheless, Bergholz thinks it’s an important place the place the venture can contribute details about what occurs throughout that brief time period.

Thus far the staff has reviewed printed literature on the topic and recognized knowledge gaps which have knowledgeable their danger mannequin. The researchers are additionally conducting laboratory experiments that simulate cooling and transportation of romaine.

Bergholz sought business enter to precisely replicate real-world eventualities.

“We’ve benefited a lot from our business companions who shared their anonymized harvest temperature knowledge,” she stated. “We may by no means have collected the 5,000 knowledge factors that they shared with us. They’ve been amassing this knowledge for years.”

“This knowledge is invaluable as a result of we have to have circumstances within the lab that make sense,” Bergholz stated. “When now we have a greater sense of the circumstances which might be truly taking place within the discipline, it helps us tremendously.”

After inoculating a number of lettuce crops with E. coli O157:H7, the researchers put them in a development chamber for a day. They then reduce the romaine and place the items in a cooler to simulate harvest and chilly storage.

Every day over a five-day interval, the researchers pull samples and assay them for the pathogen. Of specific curiosity was the pathogen’s state of dormancy.

When beneath stress, E. coli O157:H7 can transition to a dormant state labeled as both persister or viable non-culturable (VBNC) state. Within the dormant state, cells don’t reproduce, however should still trigger illness. 

When the stressor is eliminated, the metabolism of cells within the persister state can return to regular. The cells within the VBNC state can’t be cultured on an agar medium, stopping generally used detection strategies. 

As a part of the venture, the researchers plan to look at whether or not chilly storage impacts persister and VBNC transition.

“There’s nonetheless a lot that we don’t perceive concerning the persister state and the way that could be a part of the continuum into VBNC,” she stated. “We don’t know if being within the persister state impacts detection. We plan to purposely pressure cells into the persister state and decide whether or not we are able to detect them with business detection strategies.”

The analysis outcomes can be used to assist fill within the gaps of the risk-assessment mannequin, which is able to give attention to practices to scale back E. coli O157:H7 danger through the window between romaine harvest and pre-processing.

Extra about this analysis may be found here.

About CPS: The Heart for Produce Security (CPS) is a 501(c)(3), U.S. tax-exempt, charitable group centered solely on offering the produce business and authorities with open entry to the actionable info wanted to repeatedly improve the protection of recent produce.

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