Tracking an Escherichia coli O157:H7–contaminated batch of leafy greens through a pilot-scale fresh-cut processing line

Cross-contamination of fresh-cut leafy greens with residual Escherichia coli O157:H7–contaminated product during commercial processing was likely a contributing factor in several recent multistate outbreaks.

lettuceConsequently, radicchio was used as a visual marker to track the spread of the contaminated product to iceberg lettuce in a pilot-scale processing line that included a commercial shredder, step conveyor, flume tank, shaker table, and centrifugal dryer. Uninoculated iceberg lettuce (45 kg) was processed, followed by 9.1 kg of radicchio (dip inoculated to contain a four-strain, green fluorescent protein–labeled nontoxigenic E. coli O157:H7 cocktail at 106 CFU/g) and 907 kg (2,000 lb) of uninoculated iceberg lettuce. After collecting the lettuce and radicchio in about 40 bags (∼22.7 kg per bag) along with water and equipment surface samples, all visible shreds of radicchio were retrieved from the bags of shredded product, the equipment, and the floor. E. coli O157:H7 populations were quantified in the lettuce, water, and equipment samples by direct plating with or without prior membrane filtration on Trypticase soy agar containing 0.6% yeast extract and 100 ppm of ampicillin. Based on triplicate experiments, the weight of radicchio in the shredded lettuce averaged 614.9 g (93.6%), 6.9 g (1.3%), 5.0 g (0.8%), and 2.8 g (0.5%) for bags 1 to 10, 11 to 20, 21 to 30, and 31 to 40, respectively, with mean E. coli O157:H7 populations of 1.7, 1.2, 1.1, and 1.1 log CFU/g in radicchio-free lettuce. After processing, more radicchio remained on the conveyor (9.8 g; P < 0.05), compared with the shredder (8.3 g), flume tank (3.5 g), and shaker table (0.1 g), with similar E. coli O157:H7 populations (P > 0.05) recovered from all equipment surfaces after processing.

These findings clearly demonstrate both the potential for the continuous spread of contaminated lettuce to multiple batches of product during processing and the need for improved equipment designs that minimize the buildup of residual product during processing.

Journal of Food Protection®, Number 9, September 2014, pp. 1448-1648, pp. 1487-1494(8)

Buchholz, Annemarie L.1; Davidson, Gordon R.1; Marks, Bradley P.2; Todd, Ewen C.D.3; Ryser, Elliot T.

http://www.ingentaconnect.com/content/iafp/jfp/2014/00000077/00000009/art00005

Barriers to trace-back in a salad-associated EHEC outbreak, Sweden, June 2013

In June-July 2013, six counties notified the Swedish Institute for Communicable Disease Control of enterohaemorrhagic E.coli (EHEC) infections among attendees at a hotel in Dalarna, Sweden. An outbreak control team investigated to identify the source and implement control measures.

lettuce.skull.e.coli.O145We included individuals who attended the hotel between June 19th-25th in a cohort. We asked them about animal contact, swimming, and consumption of food items during this time using a questionnaire. A confirmed case was an EHEC O157:H7 outbreak strain positive individual who developed abdominal pain or diarrhoea between June 20th-July 2nd. We described the outbreak in time, place and person, calculated risk ratios (RR) and 95% confidence intervals (CI). We investigated the kitchen, tested and traced back implicated food items.

172 individuals responded. We identified 19 confirmed cases (Median age: 17 years, 64% female) with symptom onset between June 22nd-27th. Eating green salad on June 20th was associated with illness (RR:3.7;CI:1.3–11). The kitchen mixed green salads without records and destroyed leftovers immediately. Hence we could not conduct trace-back or obtain microbiological confirmation.

Green salad contaminated before entering the kitchen was the likely outbreak source. We recommended early collaboration with food agencies and better restaurant records to facilitate future investigations.

PLOS Currents Outbreaks

Michael Edelstein, Camilla Sundborger, Maria-Pia Hergens, Sofie Ivarsson, Rikard Dryselius, Mona Insulander, Cecilia Jernberg, Yvan Hutin, Anders Wallensten

http://currents.plos.org/outbreaks/article/barriers-to-trace-back-in-a-salad-associated-ehec-outbreak-sweden-june-2013/

Leafy green cone of silence: lawsuits dismissed against Tanimura & Antle

With different interpretations offered by opposing legal teams, two E. coli-related lawsuits filed by Seattle lawyer Bill Marler against Salinas-based Tanimura & Antle have been dismissed.

lettuce.skull.noroMarler told The Packer both cases had merit and were dismissed for reasons not related to the legitimacy of the cases.

Wesley Van Camp, vice president legal and general counsel for Tanimura & Antle, said the cases illustrated the importance of putting up a rigorous legal fight if there is no clear-cut connection between foodborne illnesses and specific fresh produce. She said the government must investigate to find a link between foodborne illness and specific produce items.’

In Pueblo, Colo., Tanimura & Antle had been named as a third-party defendant in an E. coli food contamination lawsuit, Liebnow vs. Boston Enterprises. The trial, which had been set for June 3, ended when the plaintiff dismissed her lawsuit against Tanimura & Antle, according to a release from the company.

Tanimura & Antle’s legal counsel was present at a mediation of the Colorado case and insisted upon dismissal of all claims against the company and defendants with prejudice, Van Camp said. The company was not a party to the settlement and no confidentiality provisions applied to Tanimura & Antle, she said.

Tanimura & Antle said in the release that a report filed by David Acheson, former associate commissioner for foods at the Food and Drug Administration, was pivotal in the case. Though a state epidemiologist had earlier named Tanimura & Antle as the lettuce supplier in the case, Acheson said in his lengthy deposition that public health officials did not conduct a full traceback of romaine lettuce and therefore could not rule out other sources of exposure. Acheson said FDA officials indicated the agency did not believe there was a compelling case to undertake the traceback on romaine lettuce.

Marler said May 3 that the Colorado case was ultimately dismissed by agreement of both parties through mediation. He said the law firm presented expert testimony that refuted Acheson’s conclusions. Timothy Jones, medical doctor and expert witness for Marler’s plaintiff, said in a report that the 2009 E. coli outbreak that caused ten cases of illness — including then 10-year old Emily Liebnow of Colorado Pueblo, Colo. Victims of the outbreak were identified in six states, including Colorado, Connecticut, Iowa, Minnesota, Missouri and North Carolina, he said. Jones said that evidence makes it “extremely unlikely” that anything other than a widely distributed food product was the source of multiple cases of illnesses caused by the E. coli O157:H7 strain.

spongebob.oil_.colbert.may3_.10-300x234“It is far more likely than not that Emily Liebnow’s infection resulted from consumption of contaminated Romaine lettuce from Tanimura and Antle, served at Giacomo’s restaurant on Sept. 6, 2009,” Jones said in this report.

In California, Marler also filed a motion to dismiss the lawsuit brought by Oroville Bernacki on behalf of his deceased wife Gail Bernacki in the U.S. District Court in Northern California against Tanimura & Antle. Tanimura & Antle’s attorney Gregory Rockwell said the plaintiff would not be able to prove that the E. coli infection resulted from the consumption of the defendant’s product.

Disputing that point, Marler said that the evidence presented in the lawsuit showed a genetic match between the woman’s illness and Tanimura & Antle product in the same time frame. Marler said the case had merit but was dismissed because the elderly plaintiff, a Canadian resident, was in declining health and was not mentally or physically up to litigation.

Fresh herbs and bagged salads can pose food safety risks

While the Canadian Food Inspection Agency was playing statistical silliness and gushing that 98 per cent of fresh leafy herbs sampled in 2009/2010 were not contaminated with bacterial pathogens or generic E. coli, researchers in Tennessee and the U.S. Centers for Disease Control published a more rigorous analysis of a multistate outbreak of Escherichia coli O157:H7 associated with bagged salad.

lettuce-skullI know; salad is not herbs. But they both have the potential to be contaminated.

Shiga toxin–producing Escherichia coli O157:H7 (STEC O157) is the most commonly identified serotype of STEC in the United States. An estimated 63,000 STEC O157 infections occur annually. Infection typically results in diarrhea, bloody stool, abdominal cramps, and, in some cases, hemolytic uremic syndrome. Recent outbreaks of STEC O157 have increasingly been associated with consumption of leafy greens such as lettuce and spinach. We investigated an outbreak of STEC O157 associated with the consumption of bagged salad with cases clustered in various institutional settings. A case–control study was conducted among cases from selected schools with controls matched by school and grade. Seventeen cases from three U.S. states were identified. The median age of cases was 23 years (range: 3–88) and 13 (76%) were female. Six cases were hospitalized and two died. Onset dates ranged from April 29 to May 12, 2012.

The matched case–control analysis identified a single significant food service exposure: consumption of lettuce provided by a school cafeteria (median odds ratio=9.4, 95% confidence interval: 1.4–∞, p=0.0469). The implicated bagged salad product was traced back to a single production facility. Implicated growing areas were scheduled for heightened inspection for the upcoming growing season. A combination of analytical epidemiologic studies among subclusters of cases, surveillance, and traceback implicated bagged salad in this outbreak investigation.

Foodborne Pathogens and Disease

Marder Ellyn P., Garman Katie N., Ingram Lily Amanda, and Dunn John R.

Internalization and fate of Escherichia coli O157:H7 in leafy green phyllosphere tissue using various spray conditions

In the past decade, leafy greens have been implicated in several outbreaks of foodborne illness, and research has focused on contamination during preharvest operations. Concerns have been raised that internalization of pathogens into the edible tissue occurs where postharvest chemical interventions would be ineffective. This study was initiated to measure the lettucedegree and fate of Escherichia coli O157:H7 internalized in the phyllosphere tissue of leafy greens when spray conditions, inoculum level, and type of leafy green were varied. Two spraying treatments were applied: (i) spraying individual spinach or lettuce leaves on plants once with a high dose (7 to 8 log CFU/ml) of E. coli O157:H7 and (ii) spraying spinach, lettuce, or parsley plants repeatedly (once per minute) with a low dose (2.7 to 4.2 log CFU/ml) of E. coli O157:H7 over a 10- to 20-min period. With the high-dose spray protocol, no significant differences in the prevalence of internalization occurred between Shiga toxin–negative E. coli O157:H7 isolates and virulent isolates (P > 0.05), implying that the Shiga toxin virulence factors did not influence internalization or the subsequent fate of those populations under these test conditions. Significantly greater internalization of E. coli O157:H7 occurred in spinach leaves compared with lettuce leaves when leaves were sprayed once with the high-dose inoculum (P < 0.05), whereas internalization was not observed in lettuce leaves but continued to be observed in spinach and parsley leaves following repeated spraying of the low-dose inoculum. Based on these results, it is surmised that a moisture film was generated when spraying was repeated and this film assisted in the mobilization of pathogen cells to plant apertures, such as stomata. E. coli O157:H7 cells that were internalized into spinach tissue using a low-dose repeat-spray protocol were temporary residents because they were not detected 2 days later, suggesting that plant-microbe interactions may be responsible.

Journal of Food Protection®, Number 5, May 2014, pp. 696-863 , pp. 713-721(9)

Erickson, Marilyn C.1; Webb, Cathy C.2; Davey, Lindsey E.2; Payton, Alison S.2; Flitcroft, Ian D.3; Doyle, Michael P.2

Just wash it doesn’t cut it; new research shows how E. coli O157:H7 binds to fresh vegetables

Research presented today at the Society for General Microbiology’s Annual Meeting in Liverpool shows that the disease-causing E. coli O157:H7 interacts directly with plant cells, allowing it to anchor to the surface of a plant, where it can multiply.

cow.poop.spinachResearchers from the James Hutton Institute in Scotland have identified that E. coli O157:H7 uses whip-link structures on its surface known as flagella – typically used for bacterial motility – to penetrate the plant cell walls. The team showed that purified flagella were able to directly interact with lipid molecules found in the membranes of plant cells. E. coli bacteria lacking flagella were unable to bind to the plant cells.

Once attached, the E. coli are able to grow on, and colonize, the surface of the plant. At this point, they can be removed by washing, although the researchers showed that a small number of bacteria are able to invade inside the plant, where they become protected from washing. The group have shown that E. coli O157:H7 is able to colonise the roots of both spinach and lettuce.

Dr Nicola Holden, who led the research, says: “This work shows the fine detail of how the bacteria bind to plants. We think this mechanism is common to many foodborne bacteria and shows that they can exploit common factors found in both cow.poop2plants and animals to help them grow. Our long term aim is to better understand these interactions so we can reduce the risk of food-borne disease.”

The researchers believe that the E. coli O157:H7 bacteria use the same method of colonizing the surface of plants as they do when colonizing the intestines of animals. The work shows that these bacteria are not simply transported through the food chain in an inert manner, but are actively interacting with both plants and animals.

Lettuce likely cause of Arizona restaurant E. coli outbreak; same in Calif.

Lettuce was the likely cause of an E. coli outbreak that sickened 94 people eating at a southwest Valley Federico’s Mexican Food restaurant, according to a report released by the Maricopa County Department of Public Health.

The outbreak occurred between July18 and 31 at the Federico’s, 13132 W. Camelback Road near Litchfield Park.

According to the report, the specific source of the bacterial exposure is uncertain, but lettuce-skulllettuce is the most likely culprit.

“The lettuce could have been contaminated in the field from manure, or (from) contaminated irrigation water, during processing, transport, handling, or through improper storage,” the report states. “Improper lettuce washing and preparation at the restaurant may have contributed to the spread of disease. The restaurant corrected these processes and complied with all other recommendations and no new cases were identified, effectively ending the outbreak.”

In California, the investigation into the cluster of E. coli cases that sickened five Humboldt County residents — including county Supervisor Estelle Fennell — has been suspended, said public health director Susan Buckley of the county Department of Health and Human Services.

”We don’t have enough cases to identify a source,” Buckley said. “They occurred over a three-month period, and showed up sporadically since August.”

What made this cluster of cases unusual was that this particular strain of E. coli — known as O157:H7 — has not been reported anywhere else in California.

After interviewing the infected Humboldt residents, Buckley said that each individual ate leafy green lettuce before feeling symptoms.

Multistate outbreak of shiga toxin-producing Escherichia coli O157:H7 infections linked to ready-to-eat salads

The lettuce and leafy greens folks always say they have some sort of food safety plan and are usually quiet when there’s an outbreak. There’s an easy solution, make data public and market at retail.

But why do that when bromides fill the market need.

A total of 33 persons infected with the outbreak strain of STEC O157:H7 were reported lettuce.skull.norofrom four states.

The number of ill persons identified in each state was as follows: Arizona (1), California (28), Texas (1), and Washington (3)

32% of ill persons were hospitalized. Two ill persons developed hemolytic uremic syndrome (HUS), and no deaths were reported.

The STEC O157:H7 PFGE pattern combination in this outbreak was new to the PulseNet database.

Epidemiologic and traceback investigations conducted by local, state, and federal officials indicated that consumption of two ready-to-eat salads, Field Fresh Chopped Salad with Grilled Chicken and Mexicali Salad with Chili Lime Chicken, produced by Glass Onion Catering and sold at Trader Joe’s grocery store locations, was the likely source of this outbreak of STEC O157:H7 infections.

On November 10, 2013, Glass Onion Catering voluntarily recalled numerous ready-to-eat salads and sandwich wrap products that may be contaminated with STEC O157:H7.

 

643 sick in separate cyclospora outbreaks

In 2005, my aunt was part of a cyclospora outbreak linked to fresh basil that struck at least 300 in Florida.

Cyclospora is miserable, until a correct diagnosis comes along and cilantro.slugs.powell.10appropriate anti-parasitics prescribed.

But cyclospora outbreaks keep popping up, year after year.

The U.S. Food and Drug Administration and Centers for Disease Control and Prevention have concluded the 2013 outbreaks were at least two different sources: fresh cilantro grown in Puebla, Mexico, felled some of those in Texas, while salad mix supplied by Taylor Farms de Mexico, S. de R.L. de C.V.,   to Olive Garden and Red Lobster restaurants, both owned by Darden Restaurants, was linked to those sick in Iowa and Nebraska.

As of September 20, 2013, CDC has been notified of 643 cases of Cyclospora infection from 25 states:  Arkansas,  California, Connecticut, Florida, Georgia, Illinois, Iowa , Kansas, Louisiana, Masssachusetts, Michigan, Minnesota, Missouri, Nebraska , New Hampshire, New Jersey, New York (including New York City), Ohio, Pennsylvania, South Dakota, Tennessee, Texas , Virginia, Wisconsin , and Wyoming. 

Food safety culture and leafy green hacks

Ever since the E. coli O157:H7 outbreak linked to bagged spinach from California in 2006 killed four and sickened 200, the leafy green folks have begged for government inspection and flogged their apparent transparency.

Anyone who brags about having government inspection has nothing to brag lettuce_skull__e_coli__O145_1_story(1)about; see XL Foods in Canada from yesterday.

And why it took 29 outbreaks before something was publicly done to allegedly improve food safety conditions remains one of those unanswered mysteries.

But for their seven years of food safety investment – which has succeeded only in lowering the Sponge Bob cone of silence over any outbreak involving California leafy greens – the best these PR flunkies can do is respond to a week-old article about food safety culture by CNN’s Dr. Gupta with a link to their own website which shows … nothing.

The phrase food safety culture has certainly jumped the shark and is bandied about by people who have no idea. I’m fairly sure Chris Griffiths came up with the phrase in the early 2000s, I used it publicly at IAFP in Calgary in 2006, based on the cultural influence of my French professor wife, and Wal-Mart Frank wrote a book about it in 2009.

Now every hack uses it.

The leafy green folks claim the LGMA website “provides access to the food safety practices, the audit checklist and annual reports which provide inspection and citation data.”

No it doesn’t.

Not anything meaningful.

And these folks are now telling Washington that food safety programs should spongebob_oil_colbert_may3_10(3)(1)(1)(1)be based on what they’ve done.

Bullshit.

If the leafy Green Marketing Folks want to be truly transparent, they will make actual inspection data public for mere mortals to review, they will market microbial food safety at retail, and stop stonewalling every time there is an outbreak linked to leafy greens.

Like the E. coli O145 outbreak that sickened 30 people in New Brunswick (that’s in Canada) in 2012.

Or the E. coli O145 linked to Romaine lettuce that sickened some 50 people in Michigan and other states in 2010.

That lettuce was grown in Arizona, but they have also adopted the LGMA model.

And were silent during the outbreak.

A table of leafy green related outbreaks is available at http://bites.ksu.edu/leafy-greens-related-outbreaks.

Multistate outbreak of Escherichia coli O145 infections associated with Romaine lettuce consumption, 2010

03.jun.13

Journal of Food Protection, Number 6, June 2013, pp. 928-1108 , pp. 939-944(6)

Taylor, E.V.; Nguyen, T.A.; Machesky, K.D.; Koch, E.; Sotir, M.J.; Bohm, S.R.; Folster, J.P.; Bokanyi, R.; Kupper, A.; Bidol, S.A.; Emanuel, A.; Arends, K.D.; Johnson, S.A.; Dunn, J.; Stroika, S.; Patel, M.K.; Williams, I.

Non-O157 Shiga toxin-producing Escherichia coli (STEC) can cause severe illness, including hemolytic uremic syndrome (HUS). STEC O145 is the sixth most commonly reported non-O157 STEC in the United States, although outbreaks have been infrequent. In April and May 2010, we investigated a multistate outbreak of STEC O145 infection. Confirmed cases were STEC O145 infections with isolate pulsed-field gel electrophoresis patterns
indistinguishable from those of the outbreak strain. Probable cases were STEC O145 infections or HUS in persons who were epidemiologically linked. Case-control studies were conducted in Michigan and Ohio; food exposures were analyzed at the restaurant, menu, and ingredient level. Environmental inspections were conducted in implicated food establishments, and food samples were collected and tested. To characterize clinical findings associated with infections, we conducted a chart review for case patients who sought medical care. We identified 27 confirmed and 4 probable cases from five states. Of these, 14 (45%) were hospitalized, 3 (10%) developed HUS, and

none died. Among two case-control studies conducted, illness was significantly associated with consumption of shredded romaine lettuce in Michigan (odds ratio [OR] = undefined; 95% confidence interval [CI] = 1.6 to undefined) and Ohio (OR = 10.9; 95% CI = 3.1 to 40.5). Samples from an unopened bag of shredded romaine lettuce yielded the predominant outbreak strain. Of 15 case patients included in the chart review, 14 (93%) had diarrhea and abdominal cramps and 11 (73%) developed bloody diarrhea. This report documents the first foodborne outbreak of STEC O145 infections in the United States. Current surveillance efforts focus primarily on E. coli O157 infections; however, non-O157 STEC can cause similar disease and outbreaks, and efforts should be made to identify both O157 and non-O157 STEC infections. Providers should test all patients with bloody diarrhea for both non-O157 and O157 STEC.

foodsafetyinfosheet-5-6-10