Reported foodborne outbreaks due to fresh produce: US vs EU

Consumption of fruit and vegetables is associated with a healthy lifestyle. Various international organizations, such as the World Health Organization, encourage the daily intake of at least 400 g of fruit and vegetables per day (excluding potatoes and other starchy tubers) for the prevention of chronic diseases, such as heart disease, cancer, diabetes, and obesity.

lettuce.skull.noroA large portion of this produce is consumed raw, and the number of foodborne outbreaks associated with these products has increased correspondingly. In this context, unpasteurized fruit juices and raw sprouts are also considered high-risk foods. The 2011 Escherichia coli O104:H4 outbreak from sprouted seeds in Germany gives a clear indication of the emerging relevance of the consumption of these products within food safety issues.

Globalization and growing international trade can also increase the risk, especially if produce comes from countries with lower safety standards. Nevertheless, nutrition educators and healthcare professionals believe that the benefits of eating fresh fruits and vegetables outweigh the risk of contracting a foodborne illness by consuming fresh produce.

The number of reported outbreaks (defined as the occurrence of two or more cases of similar illness resulting from the ingestion of a common food) reported both in the United States and European Union represents only a fraction of the actual number of outbreaks that occur.

Large outbreaks, outbreaks associated with food service and institutions, and outbreaks that have a longer duration or cause serious disease are more likely to be investigated and reported. Conversely, the data may not reflect what occurs in

sporadic cases. Moreover, there are differences in the sensitivity of the national or state systems in identifying and investigating foodborne outbreaks.

melon.berriesA wide spectrum of pathogens and food vehicles has been documented in produce-associated outbreaks. The occurrence of food-related infections due to fresh produce calls for better control interventions and the need for improved prevention strategies worldwide, since food can be contaminated at any point in the food chain, and interventions must be applied where appropriate at every step. Hence, the future success of global efforts to prevent produce-related outbreaks depends on the understanding of the key contributing factors and the maintenance of best practices to reduce and eliminate contamination.

Reported foodborne outbreaks due to fresh produce in the United States and European Union: trends and causes

Foodborne Pathogens and Disease. January 2015, 12(1): 32-38

Callejón Raquel M., Rodríguez-Naranjo M. Isabel, Ubeda Cristina, Hornedo-Ortega Ruth, Garcia-Parrilla M. Carmen, and Troncoso Ana M.

http://online.liebertpub.com/doi/abs/10.1089/fpd.2014.1821#utm_source=ETOC&utm_medium=email&utm_campaign=fpd

Abstract

The consumption of fruit and vegetables continues to rise in the United States and European Union due to healthy lifestyle recommendations. Meanwhile, the rate of foodborne illness caused by the consumption of these products remains high in both regions, representing a significant public health and financial issue. This study addresses the occurrence of reported foodborne outbreaks associated with fresh fruits and vegetables consumption in the United States and European Union during the period 2004–2012, where data are available. Special attention is paid to those pathogens responsible for these outbreaks, the mechanisms of contamination, and the fresh produce vehicles involved. Norovirus is shown to be responsible for most of the produce-related outbreaks, followed by Salmonella. Norovirus is mainly linked with the consumption of salad in the United States and of berries in the European Union, as demonstrated by the Multiple Correspondence Analysis (MCA). Salmonella was the leading cause of multistate produce outbreaks in the United States and was the pathogen involved in the majority of sprouts-associated outbreaks. As is reflected in the MCA, the pattern of fresh produce outbreaks differed in the United States and European Union by the type of microorganism and the food vehicle involved.

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Scared by the apple recall? These 5 fruits and veggies are even bigger risks

I’m still somewhat bemused that anyone has no trouble contacting me – this time while goofing around in Hawaii – yet university admin types were baffled so much they fired me for bad attendance.

Excellence in education.

lettuce.skull.noroAmy Rushlow of Yahoo! Health reports that a bacterial outbreak in apples has killed seven people and hospitalized 31, according to the Centers for Disease Control (CDC).

The Food and Drug Administration (FDA) recently confirmed that strains of listeria bacteria were discovered at the Bidart Bros. apple-packing plant in California. A majority of the cases have been linked to prepackaged caramel apples. Last week, Bidart Bros. voluntarily recalled all Granny Smith and Gala apples following the results of the tests.

Apples are the second most popular fruit in America, according the Agricultural Marketing Resource Center. But apple contamination is actually rare because they have a hard surface, which prevents bacteria from entering the fruit, says Doug Powell, PhD, a former professor of food safety in the U.S. and Canada who publishes barfblog.com.

“Fresh fruits and vegetables are probably the biggest source of foodborne illness today in North America, and that’s because they’re fresh — we don’t cook them — so anything that comes into contact has the potential to contaminate,” Powell tells Yahoo Health.

Powell is especially careful with the following five fruits and vegetables, which have been linked to a significant number of foodborne illness outbreaks over the past years. (And no, apples didn’t make the list.)

1. Sprouts

This is the one food that Powell simply refuses to eat. “There are outbreaks all the time around the world.” You might recall the 2011 outbreak in Germany, which killed more than 50 people and sickened more than 4,000. In late 2014, more than 100 Americans became ill after eating sprouts tainted with E. coli.

Sprouts are particularly prone to bacteria because they germinate in a high-temperature, high-moisture environment — the same environment where germs thrive. “They’ve shown in many of these cases, it’s the seed that’s contaminated on the inside, so then when you get it germinated, you only need one cell and it’s going to grow,” he adds.

The CDC recommends that pregnant women, children, older adults, and people with weak immune systems avoid eating raw sprouts. Cooking sprouts destroys harmful bacteria.

cantaloupe.salmonella2. Cantaloupe

Unlike honeydew melons or watermelon, cantaloupes have porous rinds that allow bacteria to enter the fruit. In addition, the fields where cantaloupes are grown often flood, Powell explains, “So they’re sitting in water, and that water may have come downstream from a livestock operation.”

3. Leafy greens

Bacteria becomes trapped on the inner leaves as the head is forming, Powell explains. Plus, leafy greens are especially difficult to wash effectively. Over the past several years in the U.S., bags of romaine lettuce, prepackaged salad mix, spinach, and spring mix have all been linked to E. coli outbreaks.

4. Tomatoes

There are several ways for germs to enter the fruit of the tomato, including via groundwater or through the water tomatoes are plunged into to give them a little shine, Powell says. “The dunk tank water has to be within five degrees of the interior of the tomato or else a vacuum is formed and water rushes in, so whatever is in dunk tank water is now inside of the tomato.” An easy fix is for tomato companies to monitor the dunk tank water, but unfortunately there isn’t a simple way for consumers to know if their grower does this.

5. Garnishes, such as green onions, cilantro, and parsley

Green onions and other herbs and vegetables used as garnishes are at high risk for outbreaks because we don’t cook them, Powell explains. He recommends leaving them off the plate if they’re simply for decoration.

Don’t let all of this scare you away from eating fresh fruits and vegetables, Powell stresses. While there is no one measure that will keep you completely safe, a few small steps can add up. For one, Powell himself shops for produce at the largest store he can find. “They have the resources to demand that their supply has to go through some basic food safety standards that they’re going to apply internally,” he says. He also recommends giving fresh produce a rinse, which removes surface debris and some (but not all) bacteria.

And while Powell doesn’t suggest always cooking fruits and vegetables to kill bacteria, since there are nutritional benefits to eating them raw, it’s a step you can take if you’re especially concerned. The FDA website offers additional everyday food safety tips.

E. coli can get airborne: Buffer zone guidelines may be inadequate to protect produce from feedlot contamination

Escherichia coli O157:H7 can spread, likely airborne, more than one tenth mile downwind from a cattle feedlot onto nearby produce, according to a paper published ahead of print in Applied and Environmental Microbiology.

lettuce.skull.noroThe high percentages of leafy greens contaminated with E. coli suggest great risk for planting fresh produce 180 m [590 feet] or less from a feedlot,” the investigators write. That suggests that current buffer zone guidelines of 120 meters [400 feet] from a feedlot may be inadequate. This is the first comprehensive and long-term study of its kind, says first author Elaine D. Berry, of the U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, in Clay Center, Nebraska.

In the study, the investigators sampled leafy greens growing in nine plots; three each at 60, 120, and 180 meters downwind from the cattle feedlot at the research center, over a two year period. The rate of contamination with the pathogenic E. coli O157:H7 declined with distance from an average of 3.5 percent of samples per plot at 60 meters to 1.8 percent at 180 meters.

The researchers sampled the produce six times between June and September of each year. They also sampled the feedlot surface manure in 10 feedlot pens for E. coli O157:H7, finding it in an average of 71.7 to 73.3 percent of samples in 2012 and 2011, respectively.  Moreover, the study’s long-term nature enabled sampling under a greater diversity of weather conditions.

A variety of conditions can affect the level of contamination, says Berry. For example, following a period of high cattle management activity when the feedlot was dry and dusty, including removal of around 300 head of cattle for shipping, the rate of total non-pathogenic E. coli-contaminated samples per plot at 180 meters shot up to 92.2 percent.

lettuceConversely, total E. coli-positive leafy green samples were notably lower on one August sample date than on any other date, a finding the investigators attribute to cleaning and removal of feedlot surface manure from the nearby pens a few weeks earlier.

The investigators also found E. coli in air samples at 180 meters from the feedlot, though the instruments were not sensitive enough to pick up E. coli O157:H7. However, the presence of E. coli in the air samples serves as a surrogate for E. coli O157:H7, demonstrating that the pathogen may also be transmitted in this manner, says Berry. The highest levels of contamination found on leafy greens, in August and September of 2012, followed several weeks of very little rainfall and several days of high temperatures, conditions that appear to abet airborne transport of bacteria from the feedlot, she says.

Limitations of the research include that it was conducted only in one state—Nebraska, which is not a produce growing state. Nonetheless, Berry says that the location was a reasonable model for some of the U.S.’s major produce growing regions, such as California’s Central Coast, as winds there can blow almost as hard as in Nebraska, and both places can have dry summers, which are conducive to airborne transport of bacteria.

The impetus for conducting the research was the rising incidence of foodborne disease outbreaks caused by contamination of fresh produce, says Berry.

If you try sometimes, you’ll get what you need: FDA says can’t have it both ways on food safety

Two of the things growers and shippers want to see in new federal food safety rules — flexibility and simplicity — are mutually exclusive according to officials from the Food and Drug Administration.

mick.taylorCoral Beach of The Packer writes the more flexible the rules, the more complicated they have to be. That was the message from FDA’s top food safety staff during a Nov. 21 session in Florida where they fielded questions on proposed rules required by the Food Safety and Modernization Act.

Mike Taylor (right, not exactly as shown), FDA deputy director of foods, and Samir Assar, director of produce safety at the FDA’s Center for Food Safety and Applied Nutrition, also said time has not been on the agency’s side in terms of developing the rules.

“It’s an incredibly rapid, very tight time frame were on,” Taylor said, adding that a court order requires the agency to publish the final rule for produce in October next year.

Taylor and other federal officials spent about 90 minutes reviewing the proposed rules and revisions before taking questions during the session, which was sponsored by the Florida Agriculture Department. It was the fifth such state session Taylor and the others have attended since Nov. 6.

(Terrible pretend playing in the video below; and this guy interviewed Nixon.)

 

Plastic or corrugated containers? Which is better for produce food safety

Two recent studies of bacteria on reusable plastic containers — both sponsored by corrugated carton groups — question the cleaning process used on RPCs before they enter the supply chain again.

reusable-plastic-containerRPC supplier IFCO and the Reusable Packaging Association has countered that no foodborne illness outbreak has been traced to RPCS.

Keith Warriner, professor of food safety at the University of Guelph in Ontario, Canada, said the study of RPCs — commissioned by the Canadian Corrugated and Containerboard Association — was an extension of one he performed in 2013. The first study tested 50 RPCs, the 2014 study involved 160 RPCs.

In the 2014 study, RPC samples from five Canadian packing facilities were pulled from different lots of trays that had been delivered on pallets wrapped with plastic film. Corrugated cartons from those facilities were not tested for comparison, Warriner said.

The study found that 13% of the RPCs tested positive for generic E. coli, but none tested positive for salmonella; 73% exceeded bacterial load levels, although that doesn’t mean they tested positive for E. coli, salmonella, listeria or other pathogens commonly associated with foodborne illness outbreaks.

“The results of the study have confirmed that a high proportion of RPCs are of poor sanitary status due to inadequate sanitation or post-cleaning contamination,” Warriner said in the study’s conclusion.

Trevor Suslow, produce safety specialist and plant pathologist at University of California-Davis, also conducted a recent study of RPCs, “Assessment of General RPC Cleanliness As Delivered for Use in Packing and Distribution of Fresh Produce.” Corrugated Delivers sponsored efforts to publicize the results and International Paper sponsored the testing.

Suslow said his research shows inconsistencies in the system for handling pooled RPCs. The difference between the Canadian study and Suslow’s is that his research tested RPCs with visible organic matter or residual produce material.

“The main takeaway from that is that we found, other than in a few cases across a few different weeks or pallet loads, the units that looked visually clean and dry had very similar viable or living microbial indicator counts compared to the ones we pulled apart for cause,” he said.

Spray-on DNA bar codes could detect pathogens on produce

Stephanie Lee of the San Francisco Chronicle, writes that to prevent and contain outbreaks of food-borne illness, which sicken 1 in 6

spray.on.dna.produceAmericans annually, a Bay Area startup is developing bar codes that go directly on fruits and vegetables. But you may overlook them: they’re DNA-size.

Using technology invented at Lawrence Livermore National Laboratory, DNATrek is creating liquids that each contain a unique DNA sequence. The odorless, colorless and tasteless solution peppers the surface of produce, or blends into other oils and liquids, with a genetic bar code that can be identified by a special machine.

The technology could solve the enormous challenge of tracing an outbreak’s source — the places where food items are grown, packed and shipped. When people start feeling the symptoms of salmonella or E. coli, many clues about the contaminated product’s origins, such as the shipment boxes, already have disappeared.

The Food and Drug Administration has already recognized the invention as a safe food additive, but for now, the industry does not use it. After large-scale tests that are set to begin next year, DNATrek believes that its tool will emerge as a powerful weapon against food-borne illnesses, which cost the country an estimated $150 billion a year in health-related expenses, and counterfeit food products, which cost the global industry $10 billion to $15 billion annually.

DNATrek suggests that its bar codes may have come in handy in 2012, when an E. coli outbreak caused by contaminated spinach led 13 people to be hospitalized, and in 2011, when 33 Americans died after eating tainted cantaloupe. “If there’s a problem at home and there’s a piece of the cantaloupe left, you can pick it out of the trash, you can scrub the surface, and all the available information is there and you know exactly where it came from,” said Anthony Zografos, founder and CEO of the self-funded, three-employee startup that expects to close a round of seed funding by the end of the month.

Safety concerns

George Farquar, a physical chemist at Lawrence Livermore, patented the product in 2010 with about $3 million in research funding from the Department of Defense. Originally conceived as a biodefense tool, it combines FDA-approved foodstuffs, such as sugar, and a unique DNA sequence to create safe, inhalable microparticles for the purposes of tracking airflow indoors and outdoors. It has been used to test whether, for instance, air detection systems are able to notice particles that resemble anthrax. Last week, company executives and scientists traveled to the Pentagon to run their third series of tests.

Farm to table: Preventing foodborne outbreaks

Monitoring pathogens for their infectious capacity in humans may not be the best approach to minimize the risk of foodborne outbreaks, say researchers who spoke during the 2014 ASM General Meeting in Boston last May.

lettuce.tomato.skullOther factors come into play—particularly, the ability of some pathogens to colonize food sources, proliferate, and thus amplify the inoculating dose delivered to consumers is critically important, they say. Colonizing food sources also can alter gene expression, increasing pathogenicity and decreasing the infectious dose. Understanding this “ecology” could prove crucial for predicting and preventing foodborne outbreaks.

Greens and produce are major sources of foodborne pathogens, many of which can thrive when greens are cut and processed during food preparation. Produce is the leading source of foodborne illness commonly caused by Salmonella enterica or Escherichia coli O157:H7 on leafy greens, according to Maria Brandl of the U.S. Department of Agriculture (USDA) in Albany, Calif.

“The continuous rise in the number of outbreaks of foodborne illness linked to fresh fruit and vegetables challenges the notion that enteric pathogens are defined mostly by their ability to colonize the intestinal habitat,” she says. “Enteric pathogens utilize diverse and overlapping strategies to interact with plants and their microflora, and to successfully colonize vertebrate hosts.”

5 Things Everyone Should Know About Washing Food (via Quest)

My friend, Matt Shipman, a science writer and public information officer at North Carolina State University writes in the below Quest North Carolina post about washing food (reprinted with permission):

464.thumbnailEverybody eats, and no one wants to eat something that could make you sick.  But there’s a lot of misinformation out there about how and whether you should wash your food.

Food safety is an important issue.  The U.S. Centers for Disease Control and Prevention estimates that each year one in six people in the United States will get sick because of food-borne illness.  And risks can be increased or decreased at every point between the farm and your fork.  Yes, you want to make sure to cook your food to the appropriate temperature, but here are some other tips to help you make good decisions in the kitchen.IMG_8159-sink-16x9-640x360

1. Don’t Wash Meat

Some people think that you’re supposed to wash chicken, turkey, or other meats before cooking.  Those people are wrong.  “Research shows that washing meat can spread dangerous bacteria around your kitchen or food preparation area,” said Ben Chapman, a food safety researcher at North Carolina State University.  “And washing poultry under running water can spray surface contamination up to three feet away.  We cook meat to make it safer; washing meat can only make a meal riskier.”

2. Washing Fruits and Veggies Only Removes up to 99 Percent of Pathogens

“That seems good, but it’s not great,” Chapman said.  By comparison, cooking food can cut the number of bacteria or other microbial pathogens by 99.9999 percent.  And that 0.9999 percent difference can be important.  If a food is contaminated by thousands of microbes, washing off 99 percent means that dozens will be left behind — and that’s enough to make you sick.  That is why people who are immunocompromised, such as some chemotherapy patients, are often discouraged from eating raw fruits and vegetables.

3. Don’t Use Soap

“Although washing has its limitations, vigorously rinsing produce under running water is the most effective way to remove the microbes that cause foodborne illnesses,” Chapman said.  You don’t need to use soap or special cleaning solutions.  In fact, using soap can actually introduce additional risk, because soaps may contain chemicals that aren’t intended for human consumption.

4. You Can’t Get All the Pesticides Off Your Food (but Don’t Panic)

Some minute traces of pesticide will probably be on — or in — your fruits or vegetables when you eat them.  “But being able to detect a pesticide doesn’t mean that it’s a public health problem,” said Chris Gunter, a researcher at NC State who studies vegetable agriculture.  That’s because, after using a pesticide, farmers are required to wait for a specific period of time before harvesting (it’s called a “pre-harvest interval”).  During that time, the pesticide breaks down or washes off, meaning any residual pesticide meets EPA’s human health requirements.

5. Even Organic Food Can Use a Rinse

Just because produce is labeled “organic” doesn’t mean that it’s somehow immune to microbial contamination. Organic farmers usually grow their fruits and vegetables in open fields, just like conventional farmers, and are subject to some of the same risks, such as fecal contamination from wildlife (that is, poop can still get on the food).

“Any time you’re going to eat fresh produce you should rinse it off, if for no other reason than to rinse off dirt,” said Don Schaffner, a food safety researcher at Rutgers.  “And rinsing off produce may offer some risk reduction in terms of microbial pathogens.”

Bonus: Don’t Wash Pre-Washed Veggies

If you’ve bought salad mix that is labeled as “pre-washed,” you really don’t need to wash it again, Schaffner said. In fact, you probably shouldn’t wash it again.  “An expert panel reported in 2007 that consumers who wash these salads again won’t reduce the risk,” Schaffner said, “and may actually create a risk of cross-contamination” where pathogens from other foods get onto the salad.  In this case, being lazy is a virtue. 

Distributions of Salmonella subtypes differ between two U.S. produce-growing regions

Salmonella accounts for approximately 50% of produce-associated outbreaks in the United States, several of which have been traced back to contamination in the produce production environment. To quantify Salmonella diversity and aid in identification of Salmonella contamination sources, we characterized Salmonella isolates from two geographically diverse produce-growing regions in the United States.

supermarket_produce Initially, we characterized the Salmonella serotype and subtype diversity associated with 1,677 samples collected from 33 produce farms in New York State (NYS). Among these 1,677 samples, 74 were Salmonella positive, yielding 80 unique isolates (from 147 total isolates), which represented 14 serovars and 23 different pulsed-field gel electrophoresis (PFGE) types. To explore regional Salmonella diversity associated with production environments, we collected a smaller set of samples (n = 65) from South Florida (SFL) production environments and compared the Salmonella diversity associated with these samples with the diversity found among NYS production environments. Among these 65 samples, 23 were Salmonella positive, yielding 32 unique isolates (from 81 total isolates), which represented 11 serovars and 17 different PFGE types.

The most common serovars isolated in NYS were Salmonella enterica serovars Newport, Cerro, and Thompson, while common serovars isolated in SFL were Salmonella serovars Saphra and Newport and S. enterica subsp. diarizonae serovar 50:r:z. High PFGE type diversity (Simpson’s diversity index, 0.90 ± 0.02) was observed among Salmonella isolates across both regions; only three PFGE types were shared between the two regions. The probability of three or fewer shared PFGE types was <0.000001; therefore, Salmonella isolates were considerably different between the two sampled regions. These findings suggest the potential for PFGE-based source tracking of Salmonella in production environments.

Appl. Environ. Microbiol. July 2014 vol. 80 no. 13 3982-3991 doi: 10.1128/AEM.00348-14

Laura K. Strawna, Michelle D. Danylukb, Randy W. Woroboa and Martin Wiedmann

http://aem.asm.org/content/80/13/3982.abstract.html?etoc

The limitations of washing fresh produce at home

A couple of weeks ago my friend Matt Shipman, who runs The Abstract, asked me to answer a question about the best way to wash produce in the home.

I’ve received different iterations of this question up from extension agents, media and at Food Safety Talk with Don Schaffner. I’ve sort of settled on this: use water, vigorously running out of the tap, but don’t expect washing to make your produce risk-free. HE_washing-pepper_s4x3_lead

I used to say that washing in the home did nothing for food safety but Don, the smart math dude I hangout with electronically, reminded me that saying it does nothing is incorrect – it does something.

Just not as much as folks may expect.

Matt captured the discussion for a blog post, below.

Here’s the question we got: “What is the most effective means of cleaning fresh produce at home to remove micro-organisms that could make you sick?”

“Vigorously rinsing the produce under running water is the most effective way of removing the microbes that cause foodborne illnesses – you don’t need soap or any special cleaning products,” says Ben Chapman, a food safety researcher at NC State. “But while washing your produce may remove some pathogens, it doesn’t eliminate risk altogether.”

“At best you get a two log reduction – that’s a 99 percent reduction in microbes,” Chapman says. “That seems good, but it’s not great. While washing can help reduce pathogen contamination, it shouldn’t be relied on as the only control measure.”

By comparison, cooking food results in a six log reduction in viable microbes. That means the population of viable microbes gets cut by 99.9999 percent(!).

The difference between 99 percent and 99.9999 percent is important because some fruits and vegetables can be contaminated with thousands of microbes. And we know that, on average, most microbial food-borne illnesses are caused by foods that are contaminated by only 20-30 organisms (the mean infectious dose for some of the pathogens of concern -ben).

So washing off 99 percent of the microbes doesn’t help much if a food was carrying thousands of microbes to start with. 

Buy from producers who know what the risks are and are employing strategies to reduce them. Ask lots of questions.

Some good references on how I’ve arrived at my answer are here: Bassett and McClure 2008Parish et al., 2003; Parnell et al., 2005; Verrill et al., 2012. There are other good ones out there too including this fact sheet from Christine Bruhn and others.