Tag Archives: Apples

Foodborne pathogen sheltered by harmless bacteria that support biofilm formation

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Pathogenic bacteria that stubbornly lurk in some apple-packing facilities may be sheltered and protected by harmless bacteria that are known for their ability to form biofilms, according to Penn State researchers, who suggest the discovery could lead to development of alternative foodborne-pathogen-control strategies. 

That was the key finding that emerged from a study of three tree-fruit-packing facilities in the Northeast where contamination with Listeria monocytogenes was a concern. The research, done in collaboration with the apple industry, was an effort to better understand the microbial ecology of food-processing facilities. The ultimate goal is to identify ways to improve pathogen control in the apple supply chain to avoid foodborne disease outbreaks and recalls of apples and apple products.

“This work is part of Penn State’s efforts to help producers comply with standards set forth in the federal Food Safety Modernization Act, often referred to as FSMA,” said researcher Jasna Kovac, assistant professor of food science, College of Agricultural Sciences. “The Department of Food Science at Penn State, through research and extension activities, has an ongoing collaboration with the apple industry, led by Luke LaBorde, professor of food science.”

The research was done in collaboration with the apple industry, in an effort to better understand the microbial ecology of food-processing facilities. The ultimate goal is to identify ways to improve pathogen control in the apple supply chain to avoid foodborne disease outbreaks and recalls of apples and apple products. 

In the study, researchers sought to understand the composition of microbiota in apple-packing environments and its association with the occurrence of the foodborne pathogen Listeria monocytogenes. Their testing revealed that a packing plant with a significantly higher Listeria monocytogenes occurrence was uniquely dominated by the bacterial family Pseudomonadaceae and the fungal family Dipodascaceae.

“As we investigated the properties of these microorganisms, we learned that they are known to be very good biofilm formers,” said lead researcher Xiaoqing Tan (upper left), a recently graduated master’s degree student in food science and a member of the Penn State Microbiome Center, housed in the Huck Institutes of the Life Sciences. “Based on our findings, we hypothesize that these harmless microorganisms are supporting the persistence of Listeria monocytogenes because they protect the harmful bacteria by enclosing them in biofilms. We are testing this hypothesis in a follow-up study.”

The findings of the research, published today (Aug. 21) in Microbiome, provide insight into the Listeria contamination problem and may lead to researchers and the apple industry getting closer to solving it, Kovac believes. Equipment in fruit-processing plants — such as brush conveyors — have a poor sanitary design that makes them difficult to clean and sanitize, she pointed out. She and LaBorde plan to work with the apple industry to devise more effective cleaning and sanitizing strategies.

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Researchers collected samples in apple-packing facilities in which Listeria monocytogenes has been persistent. They discovered that harmless bacteria may be sheltering the pathogens.

 “Following up on these findings, we are experimenting with some of the nonpathogenic strains of bacteria that are not harmful to humans to see whether they can be used as biocontrols,” she said. “Once applied on the surfaces of the equipment in these environments, they may be able to outcompete and suppress Listeria, thus reducing food-safety risks and potential regulatory action. We are still exploring that approach in a controlled laboratory environment. If it proves to be feasible, we would like to test it in apple-packing and processing facilities.”

The challenge presented by microbiota possibly sheltering Listeria monocytogenes is not limited to fruit-processing facilities or produce, Penn State researchers suspect. They will soon begin analyzing microbial communities in dairy-processing facilities to determine the microbial composition and ecology of these environments.

‘We don’t have any magic’ Kathy Glass on Listeria in apples

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Kathleen Glass started working at the University of Wisconsin-Madison Food Research Institute 30 years ago, studying various microbes — primarily those turning up in the meat and dairy industries — and assisting with food safety investigations.

caramel.appleShe added her first fruit case last year with a Listeria monocytogenes outbreak in caramel apples.

Now, Glass and other researchers are working to better understand the needs of the tree fruit industry in order to help growers, packers and retailers meet new food safety regulations and ensure the safety of their products.

“The meat and dairy industries had problems 20 years ago. That’s really when we found our religion when it comes to food safety,” Glass said.

Fruit growers didn’t have as much to worry

A couple of consecutive outbreaks with ready-to-eat meat products led to significant changes in cleaning and sanitation in that industry, Glass said, as well as the addition of growth inhibitors to meat products so that Listeria can’t grow during the normal shelf life.

The changes sparked a 42 percent decrease in cases from 1996 to 2012.

The World Health Organization estimates an infectious dose of Listeria at about 10,000 cells or more.

“Just a couple of Listeria in our food products probably is not going to make us sick. That means we need to focus on foods that support growth — perishable things you should refrigerate, those with the right amount of moisture and the right acidity level,” Glass told growers and packers at December’s Washington State Tree Fruit Association Annual Meeting in Yakima, Washington.

Investigators eventually tied the Jan. 6, 2015, Listeria outbreak to a specific supplier of Granny Smith and Gala apples in California, marking the first direct tie of fresh whole apples to a serious food safety outbreak.

road.apples .tragicallyhipBut there were some novel things about the case, Glass said. Healthy children were getting sick from an unusual food source: caramel apples.

The apples were sanitized, dipped in hot caramel, and the pH of the apples was too low for minimum growth of the pathogen, which raised several questions.

Is this the work of a superbug? Are conditions present to allow growth? Could damage to the apple contribute?

Preliminary studies suggest that damage to apples could encourage microbial growth, Glass said. In this case, puncturing the apple with a stick allowed Listeria to translocate to the core.

In addition, deep depressions in apples may protect Listeria from hot caramel. Storage temperature also is an issue, with the apples stored at room temperature at retail, enabling Listeria growth.

Glass said it’s clear the industry is stepping up its efforts in the food safety arena and in environmental testing, which is the best way to determine if there’s an area of concern.

The problem is knowing if disinfectants are as effective as hoped.

“We have to try things that have been done elsewhere and apply things in different ways,” she said. “It’s a tough, tough thing, because they don’t have a great kill step. We don’t have any magic at this point, and more research is needed.”

That’s a risk management decision: Kroger pulls caramel apples from shelves

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In the world of risk analysis the assessors calculate what’s the likelihood of a problem and present different scenarios to risk managers. And the managers weigh the consequences, options and make decisions on what to do. Like not selling unrefrigerated caramel apples anymore (or until risks can be reduced to whatever level they deem acceptable).caramel-apple

According to the Wall Street Journal, yesterday’s publication of listeria growth in caramel apples from Kathy Glass’ group at Wisconsin has led to a swift risk management decision. No more unrefrigerated caramel apples.

Kroger said it made the decision based on new scientific evidence that the product, if left unrefrigerated after being pierced with a stick, could be at risk for the bacterial disease. The grocer said it is acting out of caution after reviewing a study published by the American Society of Microbiology.

Payton Pruett, Kroger’s vice president of food safety, said Kroger believes the health risk is minimal. She (he -ben) said the company is open to carrying the caramel apples again in the future and that it will work with suppliers to reduce the risk of bacterial growth.

 

Using pigs as bug control in an orchard?

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Today the Associated Press reports that a farmer in Michigan has been using more than two dozen pigs in his organic apple orchards in his quest to control the plum curculio:

Jim Koan has gone hog-wild in his battle against a beetle that threatens his 120-acre organic apple orchard. [The] porkers patrol his orchard, gobbling down fallen, immature apples containing the beetle’s larvae. After a successful trial run late last spring, he and some researchers at Michigan State University are preparing for year two of the experiment at AlMar Orchards & Cidery in eastern Michigan.

They hope their work will someday help fruit growers throughout the world reduce the use of pesticides while diversifying their agricultural operations, as he is doing. He plans to periodically sell off the offspring of his four original hogs, keeping only what he needs.

Interesting move, definitely thinking outside the box, as organic producers must, when it comes to pest control. I wonder if there is a segment of the research that looks at the microbiological differences between the fresh apples (and the drops) on his farm and other producers not using the hogs.  This pest reduction plan might be introducing new food safety risks that weren’t there before.

Feral pigs seemed to play a part in the the 2006 spinach outbreak. Last March the FDA said: "Potential environmental risk factors for E.coli O157:H7 contamination at or near the field included the presence of wild pigs, the proximity of irrigation wells used to grow produce for ready-to-eat packaging, and surface waterways exposed to feces from cattle and wildlife."