Leafy greens carry risks; at-home rinsing of pre-washed salad mix isn’t doing much

In the quest to get healthier, including losing weight and reducing my body fat percentage, I’ve been paying particular attention to my eating habits and eating a bunch more vegetables.

I’ve become increasingly fond of the convenience of pre-washed, bagged, fresh whatever. A staple of my weekly meals is 4oz of steak, a crumble of blue cheese, grilled mushrooms, sliced pear, a few walnuts all over a bed of 50/50 mix of pre-washed baby spinach and and mesclun mix.img86l

I just open the bag and throw it on the plate. Because there’s not much I can do, safety-wise, to it once it’s in my home. If there’s pathogenic E. coli, Listeria or Salmonella there (or others) I’m stuck with it. I’m following recommendations from a bunch of my food safety friends who reviewed the literature on cut, bagged, washed, ready-to-eat leafy greens from a few years ago. In the abstract, they write:

The panel concluded that leafy green salad in sealed bags labeled “washed” or “ready-to-eat” that are produced in a facility inspected by a regulatory authority and operated under cGMPs, does not need additional washing at the time of use unless specifically directed on the label.

Leafy green food safety risks need to be addressed before they get to me, all I can do by washing it again is increase the chance I cross-contaminate the salad precursor in my home. My purchasing choice is based in trust that growers, packers and processors know what they are doing, and do it. But at best, they can only remove 90% of what is there with a wash.

Last week some research was presented at the American Chemical Society National Meeting & Exposition, prior to peer-review, that states what lots of food safety folks have published over the past decade: washing leafy greens doesn’t result in a sterile salad and the bumpy leaves protect pathogens.

Yep.

I talked to Korin Miller at Yahoo News about it,

Labels like “thoroughly washed” and “triple washed” make us feel comfortable chowing down on pre-washed baby spinach straight from the container. But researchers from the University of California, Riverside, say we might want to rethink that habit.

They discovered that the small peaks and valleys in baby spinach leaves can harbor bacteria — even during the washing process they often undergo in food-processing plants.

While the news is shocking to most people, “this is not a surprise to many of us in the food safety arena,” Mike Doyle, director of the Center for Food Safety at the University of Georgia, tells Yahoo Health.

Unfortunately, washing your pre-washed baby spinach before eating it doesn’t make a difference, says Benjamin Chapman, PhD, an assistant professor and food safety extension specialist at North Carolina State University.

“Rinsing isn’t going to do a whole heck of a lot for food safety,” Chapman tells Yahoo Health — it just may remove dirt or other physical objects that you can see. Cooking the spinach, however, will kill potentially harmful bacteria.

I don’t agree with this comment, ‘pre-washed baby spinach is typically treated using a bleach disinfectant’

But what about the whole “triple wash” label? Does that make pre-washed spinach safer? Chapman says there’s some confusion about what it means. Companies don’t triple wash spinach to disinfect it, he explains — they do it to reduce the likelihood of cross-contamination from one piece of spinach to another during the washing process.

The water is treated to reduce cross-contamination in the processing water; 2-log reduction, at the very best, is not an effective surface disinfectant.

Leafs are bumpy: Change in disinfecting spinach, salad greens could reduce illness

Cross contamination in commercial processing facilities that prepare spinach and other leafy greens for the market can make people sick. But researchers are reporting a new, easy-to-implement method that could eliminate or reduce such incidences.

howcleanisyoThe scientists will present their work at the 250th National Meeting & Exposition of the American Chemical Society (ACS).

Spinach or other leafy salad greens were responsible for 18 food-poisoning outbreaks over the last decade.

Greens are washed by commercial processes before they head to the grocery store. But these methods, which can include water and bleach rinses or irradiation, are not completely effective, says Nichola Kinsinger, Ph.D. She says scientists have estimated that 99 percent of food-borne illnesses from leafy greens can be traced back to disinfection issues. As a result, they have searched for and developed a different approach to attacking the bacteria, most notably E. coli, which is the cause of many outbreaks.

“Despite current disinfection rinsing, bacteria are surviving on the leaf and causing cross contamination, resulting in the numerous outbreaks we hear about in the media,” Kinsinger says. She is a postdoc in the lab of Sharon Walker, Ph.D., at the University of California, Riverside. “Pathogens can come from irrigation waters or from water used during processing, and they can adhere to spinach leaves. If these bacteria are not all killed in the disinfection process, they can continue to live, grow, spread and contaminate other surfaces within the facility and other leaves.”

Using a parallel-plate flow chamber system that Walker developed, the researchers tested the real-time attachment and detachment of bacteria to the outer layer of spinach leaves. At low bleach concentrations, the bacteria fell off the leaves, but remained alive. At the higher concentrations used commercially, however, all of the bacteria were killed. “This result was perplexing,” Walker says. “Our experiments were telling us that commercial bleach rinses should be much more effective than they are. But then we studied the leaf itself in more detail.”

A spinach leaf is not perfectly smooth, she notes. So, the team modeled how the bleach would move across the surface of a spinach leaf, taking its bumps and grooves into account. Surprisingly, the model revealed that the concentrations of bleach on leaves may not be consistent.

“We found that because of the topology of the spinach leaf, nearly 15 percent of the surface may ‘see’ a bleach concentration that is 1,000-times less than that of the rinse solution,” Kinsinger says. In some cases, that translated to a 90 percent bacterial survival in their tests—and a high risk for cross contamination.

To reduce that risk, the researchers are optimizing an inexpensive titanium dioxide (TiO2) photocatalyst that companies could add to the rinse water or use to coat equipment surfaces that come into contact with the leaves as they are processed. When TiO2 absorbs light, it produces a strong oxidant that kills bacteria.

The scientists now plan to conduct more studies on the photocatalyst, and they will look at a broader range of foods, engineered surfaces and pathogens.

 

Irrigation water, produce and pathogens

The microbiological sanitary quality and safety of leafy greens and strawberries were assessed in the primary production in Belgium, Brazil, Egypt, Norway and Spain by enumeration of Escherichia coli and detection of Salmonella, Shiga toxin-producing E. coli (STEC) and Campylobacter.

strawberryWater samples were more prone to containing pathogens (54 positives out of 950 analyses) than soil (16/1186) and produce on the field (18/977 for leafy greens and 5/402 for strawberries). The prevalence of pathogens also varied markedly according to the sampling region. Flooding of fields increased the risk considerably, with odds ratio (OR) 10.9 for Salmonella and 7.0 for STEC.

A significant association between elevated numbers of generic E. coli and detection of pathogens (OR of 2.3 for STEC and 2.7 for Salmonella) was established. Generic E. coli was found to be a suitable index organism for Salmonella and STEC, but to a lesser extent for Campylobacter. Guidelines on frequency of sampling and threshold values for E. coli in irrigation water may differ from region to region. 

Risk Factors for Salmonella, shiga toxin-producing Escherichia coli and Campylobacter occurrence in primary production of leafy greens and strawberries

International Journal of Environmental Research and Public Health

Siele Ceuppens, Gro S. Johannessen, Ana Allende, Eduardo César Tondo,  Fouad El-Tahan, Imca Sampers, Liesbeth Jacxsens, and  Mieke Uyttendaele

http://www.mdpi.com/1660-4601/12/8/9809

Canada, how long does it take to write a PR? 13 sick with E. coli infections and possible link to leafy greens

The leafy greens cone of silence continues to silence or impair epidemiology across North America.

leafy.green.lettuceThe Public Health Agency of Canada says today that 13 people across Canada were sickened with E. coli O157:H7 with a possible link to leafy greens, and that the investigation concluded on May 12, 2015.

Two weeks is a long time to get approval for a simple press release.

“Although leafy greens were identified as a possible source of illness, a specific source of the outbreak could not be confirmed.

“During the investigation, exposure to leafy greens was identified as a possible source of illness. Leafy greens can include all varieties of lettuces and other green leaf vegetables such as kale, spinach, arugula, or chard. The Canadian Food Inspection Agency conducted an investigation into leafy greens, however no specific food products were identified as the source of the outbreak.”

And the usual boilerplate:

waynes-world-monkeys-might-fly-out--e1297873880696“Canadians are reminded to always follow safe food handling practices to avoid illness. Wash your hands thoroughly before preparing or eating food. Wash raw fruits and vegetables thoroughly with clean, safe running water before you prepare and eat them.”

Yup, 13 people from Alberta to Newfoundland got sick with the same E. coli because of bad handwashing (not).

It’s the season, not the farm, silly (and the poop): E. coli and leafy greens in US

Small- and medium-size farms in the mid-Atlantic region of the United States use varied agricultural practices to produce leafy greens during spring and fall, but the impact of preharvest practices on food safety risk remains unclear.

lettuceTo assess farm-level risk factors, bacterial indicators, Salmonella enterica, and Shiga toxin-producing Escherichia coli (STEC) from 32 organic and conventional farms were analyzed.

A total of 577 leafy greens, irrigation water, compost, field soil, and pond sediment samples were collected. Salmonella was recovered from 2.2% of leafy greens (n = 369) and 7.7% of sediment (n = 13) samples. There was an association between Salmonella recovery and growing season (fall versus spring) (P = 0.006) but not farming system (organic or conventional) (P = 0.920) or region (P = 0.991). No STEC was isolated.

In all, 10% of samples were positive for E. coli: 6% of leafy greens, 18% of irrigation water, 10% of soil, 38% of sediment, and 27% of compost samples. Farming system was not a significant factor for levels of E. coli or aerobic mesophiles on leafy greens but was a significant factor for total coliforms (TC) (P < 0.001), with higher counts from organic farm samples. Growing season was a factor for aerobic mesophiles on leafy greens (P = 0.004), with higher levels in fall than in spring. Water source was a factor for all indicator bacteria (P < 0.001), and end-of-line groundwater had marginally higher TC counts than source samples (P = 0.059).

Overall, the data suggest that seasonal events, weather conditions, and proximity of compost piles might be important factors contributing to microbial contamination on farms growing leafy greens.

The growing season, but not the farming system, is a food safety risk determinant for leafy greens in the mid-Atlantic region of the United States

Applied and Environmental Microbiology

Sasha C. Marine, Sivaranjani Pagadala, Fei Wang, Donna M. Pahl, Meredith V. Melendez, Wesley L. Kline, Ruth A. Oni, Christopher S. Walsh, Kathryne L. Everts, Robert L. Buchanan, and Shirley A. Micallef

http://aem.asm.org/content/81/7/2395.abstract?etoc

A repeated cross-sectional study was conducted to identify farm management, environment, weather, and landscape factors that predict the count of generic Escherichia coli on spinach at the preharvest level.

E. coli was enumerated for 955 spinach samples collected on 12 farms in Texas and Colorado between 2010 and 2012. Farm management and environmental characteristics were surveyed using a questionnaire. Weather and landscape data were obtained from National Resources Information databases.

lettuce.tomato.skullA two-part mixed-effect negative binomial hurdle model, consisting of a logistic and zero-truncated negative binomial part with farm and date as random effects, was used to identify factors affecting E. coli counts on spinach.

Results indicated that the odds of a contamination event (non-zero versus zero counts) vary by state (odds ratio [OR] = 108.1). Odds of contamination decreased with implementation of hygiene practices (OR = 0.06) and increased with an increasing average precipitation amount (mm) in the past 29 days (OR = 3.5) and the application of manure (OR = 52.2).

On contaminated spinach, E. coli counts increased with the average precipitation amount over the past 29 days. The relationship between E. coli count and the average maximum daily temperature over the 9 days prior to sampling followed a quadratic function with the highest bacterial count at around 24°C.

These findings indicate that the odds of a contamination event in spinach are determined by farm management, environment, and weather factors. However, once the contamination event has occurred, the count of E. coli on spinach is determined by weather only.

Multifactorial effects of ambient temperature, precipitation, farm management, and environmental factors determine the level of generic Escherichia coli contamination on preharvested spinach

Applied and Environmental Microbiology

Sangshin Park, Sarah Navratil, Ashley Gregory, Arin Bauer, Indumathi Srinath, Barbara Szonyi, Kendra Nightingale, Juan Anciso, Mikyoung Jun, Daikwon Han, Sara Lawhon, and Renata Ivanek

http://aem.asm.org/content/81/7/2635.abstract?etoc

Modeling Listeria in leafy greens using micro and big data

I’m not sure what big data means, but it’s a catchy soundbite that is showing up more routinely.

lettuce.skull.noroProf. Martin Wiedmann, food science and technology, has combined the fields of microbiology and big data to better predict disease outbreaks and preserve food safety.

Wiedmann conducted a study focused on Listeria monocytogenes bacteria and related Listeria species — a leading cause of foodborne illnesses and deaths.

“The main goal of the study was to find better ways to determine whether lettuce or similar produce grown in a field are likely to have bacteria on them that could make you sick if you eat the product,” Wiedmann said.

According to Wiedmann, there are about 1,600 cases of Listeriosis annually in the United States, with more than 20 percent of those infections resulting in death.

“It is definitely not your middle-of-the-road food poisoning disease, which makes [Listeria] so important to understand and study,” Wiedmann said.

Normally, raw and unprocessed foods will be preserved with refrigeration or salting to prevent bacterial growth. Listeria can grow under refrigeration temperatures and high salt environments, thus making these typical methods ineffective at killing off the bacteria.

Products that are taken directly from growing conditions and consumed are high risk produce. They are the foods most likely to transmit foodborne pathogens — unless necessary precautions are taken.

“Therefore, it is necessary to make sure the product is safe and free of these pathogens while it is still in the field,” Wiedmann said.

Wiedmann and colleagues collected many samples from various farms in upstate New York.

“In addition to isolating Listeria species from the sample, we also collected Geographic Information System data (GIS), which records the exact location of where the sample was collected,” Wiedmann said. “With this, we can ask questions such as how close was Sample A to water or to a major road?”

Wiedmann uses the data to understand the factors that are conducive to Listeria growth.

Analysis of the data revealed that proximity to water is a major factor of a high risk Listeria presence.

“The analysis of the data allows us to predict high and low risk areas for Listeria and also see whether different types of the bacteria behave differently,” Wiedmann said.

He has also started working on collecting data for Salmonella and Escherichia coli, two other very important foodborne pathogens. According to Wiedmann, the next steps will be to analyze different states and regions in conjunction with different pathogen species to better understand food production and the pathogens that afflict it.

Salmonella and raw leafy greens most dangerous according to EU risk assessment model

Foods of non-animal origin (FoNAO) are consumed in a variety of forms, being a major component of almost all meals. These food types have the potential to be associated with large outbreaks as seen in 2011 associated with VTEC O104.

lettuce.skull.noroIn order to identify and rank specific food/pathogen combinations most often linked to human cases originating from FoNAO in the EU, a semi-quantitative model was developed using seven criteria: strength of associations between food and pathogen based on the foodborne outbreak data from EU Zoonoses Monitoring (2007–2011), incidence of illness, burden of disease, dose–response relationship, consumption, prevalence of contamination and pathogen growth potential during shelf life.

The top ranking food/pathogen combination was Salmonella spp. and leafy greens eaten raw followed by (in equal rank) Salmonella spp. and bulb and stem vegetables, Salmonella spp. and tomatoes, Salmonella spp. and melons, and pathogenic Escherichia coli and fresh pods, legumes or grains.

Despite the inherent assumptions and limitations, this risk model is considered a tool for risk managers, as it allows ranking of food/pathogen combinations most often linked to foodborne human cases originating from FoNAO in the EU. Efforts to collect additional data even in the absence of reported outbreaks as well as to enhance the quality of the EU-specific data, which was used as input for all the model criteria, will allow the improvement of the model outputs. Furthermore, it is recommended that harmonised terminology be applied to the categorisation of foods collected for different reasons, e.g. monitoring, surveillance, outbreak investigation and consumption. In addition, to assist future microbiological risk assessments, consideration should be given to the collection of additional information on how food has been processed, stored and prepared as part of the above data collection exercises.

Risk ranking of pathogens in ready-to-eat unprocessed foods of non-animal origin (FoNAO) in the EU: Initial evaluation using outbreak data (2007–2011)

International Journal of Food Microbiology, Volume 195, 16 February 2015, Pages 9–19

M.T. Da Silva Felícioa, , , T. Haldb, E. Liebanaa A. Allendec, M. Hugasa, C. Nguyen-Thed, e, G. Skoien Johannessenf, T. Niskaneng, M. Uyttendaeleh, J. McLauchlin

http://www.sciencedirect.com/science/article/pii/S0168160514005443

Can E. coli O157:H7 blow from feedlots to lettuce or spinach fields? (Yes) Does it matter? (Probably)

The impact of proximity to a beef cattle feedlot on E. coli O157:H7 contamination of leafy greens was examined. In each of two years, leafy greens were planted to nine plots located 60, 120, and 180 meters from a cattle feedlot (3 plots each distance).

cattle.lettuceLeafy greens (270) and feedlot manure samples (100) were collected six different times from June to September in each year. Both E. coli O157:H7 and total E. coli were recovered from leafy greens at all plot distances.

E. coli O157:H7 was recovered from 3.5% of leafy green samples per plot at 60 meters, which was higher (P < 0.05) than the 1.8% of positive samples per plot at 180 meters, indicating a decrease in contamination as distance from the feedlot was increased. Although E. coli O157:H7 was not recovered from air samples at any distance, total E. coli was recovered from air samples at the feedlot edge and all plot distances, indicating that airborne transport of the pathogen can occur.

Results suggest that risk for airborne transport of E. coli O157:H7 from cattle production is increased when cattle pen surfaces are very dry, and when this situation is combined with cattle management or cattle behaviors that generate airborne dust.

cow.poop2__1.storyCurrent leafy green field distance guidelines of 120 meters (400 feet) may not be adequate to limit the transmission of E. coli O157:H7 to produce crops planted near concentrated animal feeding operations. Additional research is needed to determine safe set-back distances between cattle feedlots and crop production that will reduce fresh produce contamination.

Effect of Proximity to a Cattle Feedlot on Escherichia coli O157:H7 Contamination of Leafy Greens and Evaluation of the Potential for Airborne Transmission

01.dec.14

Applied and Environmental Microbiology

Elaine D. Berry, James E. Wells, James L. Bono, Bryan L. Woodbury, Norasak Kalchayanand, Keri N. Norman, Trevor V. Suslow, Gabriela López-Velasco and Patricia D. Millner

http://aem.asm.org/content/early/2014/11/24/AEM.02998-14.abstract

Evaluation? E. coli victims appeal to workers in LGMA training video

Coral Beach of The Packer writes that victims of the 2006 E. coli outbreak linked to fresh spinach tell their stories in a new food safety training video co-produaced by the California Leafy Greens Marketing Agreement and the non-profit group STOP Foodborne Illness.

Lauren Bush tells her story in the video, describing how as a 20-year-old college student she contracted an infection from a spinach salad that ultimately sent her to the hospital with hemorrhaging and other severe symptoms.

“I’m so pleased with the video,” Bush said during a Nov. 19 Internet press conference. “I hope it reminds everyone who sees it of the importance of what they are doing. I know it must be a lot of extra work, but it does save lives.”

Dan Sutton, LGMA member and general manager of Pismo Oceano Vegetable Exchange, said he attended a training session a week before the press conference and watched the reactions of people seeing it for the first time.

“There was absolute silence when it was over,” Sutton said. “It had an impact.”

The video is bilingual with segments presented in Spanish and English.

Leafy greens cone of silence; Phoenix E. coli victim sues Trader Joe’s, salad maker

A Phoenix man is suing Trader Joe’s and Glass Onion Catering and Gourmet Foods, the manufacturer of ready-to-eat salads that were linked to an outbreak of a deadly strain of E. coli last year that sickened 33 people in four Western states.

spongebob.oil.colbert.may3.10Steven Rabinowitz was the only Arizona resident who became seriously ill after eating the salads, which were sold at Trader Joe’s stores in the West. Seven others who were sickened also have sued.

The outbreak has been traced back to romaine lettuce produced in a single field, grown directly across from a cattle operation in Modesto, Calif. The strain of E. coli linked to the outbreak is most commonly found in cattle manure.

State public-health investigators from California could not determine a root cause of the outbreak, but they believe contaminants from the cattle field may have blown on to the lettuce grown by Ratto Bros., according to the investigative report. The grower has improved and adopted new procedures to prevent future contamination, the report says.

The case highlights the responsibility of everyone involved in the farm-to-table continuum — including growers, manufacturers and sellers — because consumers have no control over how a pre-packaged product is made, said Bill Marler, a Seattle attorney representing Rabinowitz and the other victims in the outbreak.

“There’s no consumer intervention here at all. You’re not going to buy a pre-made salad, take it out and wash it, and put it back in again,” said Marler, a national expert who has represented food-poisoning victims for more than 20 years. “Frankly, that’s why we sued. … This really requires more responsibility on the part of the entity that’s selling you the product.”