The continuing prevalence of shiga-toxin producing E. coli in produce

Chris Koger of The Packer writes the U.S. Centers for Disease Control and Prevention has added 16 more people to an E. coli outbreak investigation of unknown origin, bringing the total to 39. Cases have been reported in 18 states; there have been no deaths.

According to the CDC’s Nov. 23 update, “Of the 22 ill people interviewed to date, all reported eating a variety of leafy greens, like spinach (16), romaine lettuce (15), iceberg lettuce (12), and mixed bag lettuce (8). No single type or brand of leafy greens or other food item has been identified as the source of this outbreak. CDC is not advising people avoid any particular food at this time.

Dole Fresh Vegetables, Inc. is voluntarily recalling a limited number of cases of organic romaine hearts. The products being recalled are Dole™ Organic Romaine Hearts 3pk (UPC 0-71430-90061-1), combined English/French packaging, with Harvested-On dates of 10-23-20 and 10-26-20, and Wild Harvest Organic Romaine Hearts (UPC 7-11535-50201-2), with Harvested-On dates of 10-23-20 and 10-26-20.  The recall is being conducted due to a possible health risk from E. coli in the two products.  Dole Fresh Vegetables is coordinating closely with regulatory officials. No illnesses have been reported to date in association with the recall. 

Pathogenic E. coli can cause diarrhea, severe stomach cramps and vomiting.  Most people recover within a week, but some illnesses can last longer and can be more severe.

This precautionary recall notification is being issued due to an isolated instance in which a package of Dole™ Organic Romaine Hearts – 3pk yielded a positive result for pathogenic non-O157 E.coli STEC in a routine sample collected at a retail store by the Michigan Department of Agriculture and Rural Development. There is no indication at this time that this positive result is related to any illnesses nor consumer complaints and it is not associated with the strains connected to the ongoing outbreaks currently under regulatory investigation. 

Spice risk: Cilantro and dangerous E. coli

I tell people that spices like cilantro are a significant source of dangerous E. coli and they look at me like I just fell off the turnip truck.

This study sought to model the growth and die-off of Escherichia coli (E. coli) O157:H7 along the cilantro supply chain from farm-to-fork to investigate its risk to public health. Contributing factors included in the model were on farm contamination from irrigation water and soil, solar radiation, harvesting, and transportation and storage times and temperatures.

The developed risk model estimated the microbiological risks associated with E. coli O157:H7 in cilantro and determined parameters with the most effect on the final concentration per serving for future mitigation strategies. Results showed a similar decrease in the E. coli O157:H7 (median values) concentrations along the supply chain for cilantro grown in both winter and summer weather conditions. With an estimated 0.1% prevalence of E. coli O157:H7 contamination for cilantro post-harvest used for illustration, the model predicted the probability of illness from consuming fresh cilantro as very low with fewer than two illnesses per every one billion servings of cilantro (1.6 x 10-9; 95th percentile). Although rare, 3.7% and 1.6% of scenarios run in this model for summer and winter grown cilantro, respectively, result in over 10 cases per year in the United States.

This is reflected in real life where illnesses from cilantro are seen rarely but outbreaks have occurred. Sensitivity analysis and scenario testing demonstrated that ensuring clean and high quality irrigation water and preventing temperature abuse during transportation from farm to retail, are key to reducing overall risk of illness.

Evaluation of public health risk for Escherichia coli O157:H7 in cilantro, 16 July 2020

Food Research International

eTaryn Horr and Abani Pradhan

https://doi.org/10.1016/j.foodres.2020.109545

https://www.sciencedirect.com/science/article/abs/pii/S0963996920305706

Brits like their tea – it’s not local

In this study, the persistence of toxigenic Escherichia coli (E. coli ) on dried chamomile, peppermint, ginger, cinnamon, black and green teas stored under 4, 10, and 25°C was determined.

The E. coli survival rate in ginger and cinnamon teas decreased below 0 on Day 5. In the other tested teas, E. coli survivability showed a downward trend over time, but never dropped to 0. Chamomile tea retained the greatest population of viable E. coli . Meanwhile, die‐off of E. coli was higher at 25°C compared to lower temperatures. Additionally, fate of E. coli during brewing at 60, 70 and 80°C was evaluated.

The E. coli population was reduced to below 2 Log colony forming units (CFU)/g after 1 min at 80°C, At the same time, the E. coli survival at 60°C was higher than that at 70°C in all tested teas. The data indicated that if E. coli survives after storage of prepared teas, it may also survive and grow after the brewing process, especially if performed using temperatures <80°C. Finally, we analyzed the correlations between temperature, time, tea varieties and E. coli survival, and successfully constructed a random forest regression model. The results of this study can be used to predict changes in E. coli during storage and fate during the brewing process. Results will form the basis of undertaking a risk assessment.

Survival of toxigenic Escherichia coli on chamomile, peppermint, green, black, ginger, and cinnamon teas during storage and brewing, 23 June 2020

Journal of Food Safety

Yanan Liu, Fan Wu, Yan Zhu, Yirui Chen, Kayla Murray, Zhaoxin Lu, Keith Warriner

https://doi.org/10.1111/jfs.12831

https://onlinelibrary.wiley.com/doi/abs/10.1111/jfs.12831

Tough mudders beware: there is E. coli risk

In August 2018, Public Health England (PHE) was made aware of five probable cases of Shiga toxin‐producing Escherichia coli (STEC) O157:H7 among individuals reporting participation in a mud‐based obstacle race. An additional four cases, identified via routine whole‐genome sequencing, were subsequently linked to the same event. Two of the nine cases were due to secondary household transmission.

Despite an agreement between the event organizers and the local authority, to ensure that all livestock were removed from the site 28 days before the event, sheep were observed grazing on some of the routes taken by the runners 2 days prior to the race taking place. A retrospective review of incidents reported to PHE between 2015 and 2018 identified 41 cases of gastroenteritis associated with muddy assault course events. Of these, 25 cases were due to infection with STEC O157:H7, of which all but one were associated with outbreaks.

Due to the environment in which such events take place, it is impossible to entirely remove the risk of exposure to potentially pathogenic zoonoses. However, race organizers should ensure that livestock are removed from the course 28 days before the event. They should also ensure that participants are made aware of the risk of contracting gastrointestinal disease from the environment, and to stress the importance of hand hygiene post‐event and the risk of secondary transmission, particularly to children who are at risk of developing haemolytic uraemic syndrome.

An outbreak of shiga toxin-producing Escherichia coli O157:H7 linked to a mud-based obstacle course, England, August 2018

Zoonoses and Public Health

Alexander Sharp, Elizabeth Smout, Lisa Byrne, Rebecca Greenwood, Richard Abdoollah, Charlotte Hutchinson, Claire Jenkins, Nachi Arunachalam, Simon Padfield, Gareth Hughes, Mike Gent

https://doi.org/10.1111/zph.12744

https://onlinelibrary.wiley.com/doi/abs/10.1111/zph.12744

Ya don’t know unless ya test

Ya can’t test your way to a safe food supply, but ya can test to verify your food safety plans are working.

Testing to Additional Raw Beef Products

AGENCY: Food Safety and Inspection Service, USDA.

ACTION: Notice and request for comments.

SUMMARY: The Food Safety and Inspection Service (FSIS) is announcing plans to expand its routine verification testing for six Shiga toxin-producing Escherichia coli (non-O157 STEC; O26, O45, O103, O111, O121, or O145) that are adulterants, in addition to the adulterant Escherichia coli (E. coli) O157:H7, to ground beef, bench trim, and raw ground beef components other than raw beef manufacturing trimmings (i.e., head meat, cheek meat, weasand (esophagus) meat, product from advanced meat recovery (AMR) systems, partially defatted chopped beef and partially defatted beef fatty tissue, low temperature rendered lean finely textured beef, and heart meat)(hereafter “other raw ground beef components”) for samples collected at official establishments. STEC includes non-O157 STEC; O26, O45, O103, O111, O121, or O145, that are adulterants, and E. coli O157:H7. Currently, FSIS tests only its beef manufacturing trimmings samples for these six non-O157 STEC and E. coli O157:H7; all This document is scheduled to be published in the Federal Register on 06/04/2020 and available online at federalregister.gov/d/2020-12073, and on govinfo.gov 2 other aforementioned raw beef products are presently tested for E. coli O157:H7 only.

FSIS also intends to test for these non-O157 STEC in ground beef samples that it collects at retail stores and in applicable samples it collects of imported raw beef products. FSIS is requesting comments on the proposed sampling and testing of ground beef, bench trim, and other raw ground beef components. FSIS will announce the date it will implement the new testing in a subsequent Federal Register notice. Additionally, FSIS is responding to comments on the November 19, 2014, Federal Register notice titled “Shiga Toxin Producing Escherichia coli (STEC) in Certain Raw Beef Products.” FSIS is also making available its updated analysis of the estimated costs and benefits associated with the implementation of its non-O157 STEC testing on raw beef manufacturing trimmings and the costs and benefits associated with the expansion of its non-O157 STEC testing to ground beef, bench trim, and other raw ground beef components.

Raw is still risky: Six years after a toddler died, Australian advocates want raw milk back on the table

In late 2014, three children in the Australian state of Victoria developed hemolytic uremic syndrome linked to Shiga-toxin toxin producing E. coli in unpasteurized bath milk produced by Mountain View Dairy Farm. One child died, and two others developed cryptosporidiosis.

The Victorian government quickly banned the sale of so-called bath milk, which although labeled as not fit for human consumption, was a widely recognized way for Australian consumers to access raw milk.

What followed was a despicable whisper campaign that the child who died had an underlying medical condition, it wasn’t Shiga-toxin producing E. coli (STEC), farmers were losing access to lucrative markets – anything but the basic and sometimes deadly biology of STECs and everything involving fantasy and fairytales.

Victorian Dairy farmer Vicki Jones was told in 2014 by the coroner that raw milk was the likely cause of death of a three-year-old boy in 2014.

The milk was ‘raw’, or unpasteurised, and Ms Jones’ Mountain View Dairy Farm had been selling it as bath milk — a cosmetic product labelled ‘not fit for drinking’. 

Ms Jones said she told the officer she would immediately remove the milk from the shelves of local stores. 

“And he said to me, ‘No, no, no, don’t do that. You’ve done nothing wrong and all your labelling is right’.”

In hindsight, Ms Jones said this response “was really bizarre” — as was the decision to wait months before telling her about the cases.

But then the health officer told her a three-year-old boy had died after drinking the bath milk. 

“It was the most devastating news that you could possibly imagine ever getting,” she said.

“I was mortified, we were doing the raw milk because people wanted it.”

Or because you contributed to promoting BS.

A Gippsland MP, the father of the child who died, and evidence presented to the coroner have all questioned how the cases were managed and suggested other contributing factors were overlooked.

Mark Wahlqvist, an Emeritus professor of medicine at Monash University and former president of the international union of nutrition sciences, said, “Raw milk, unpasteurised milk, is not safe enough to be in the public domain.”

Professor Wahlqvist said he was open to new research but at present, found campaigners for raw milk to be more than unconvincing.

“When people for conspiratorial reasons rather than scientific reasons, think that vaccination is a problem or that pasteurisation is a problem,” he said.

“We have a science communication problem in this country and it needs science leaders.”

STEC O91 may help with the others

Shiga toxin-producing Escherichia coli (STEC) strains are important zoonotic foodborne pathogens, causing diarrhea, hemorrhagic colitis, and life-threatening hemolytic uremic syndrome (HUS) in humans. However, antibiotic treatment of STEC infection is associated with an increased risk of HUS. Therefore, there is an urgent need for early and effective therapeutic strategies.

Here, we isolated lytic T7-like STEC phage PHB19 and identified a novel O91-specific polysaccharide depolymerase (Dep6) in the C terminus of the PHB19 tailspike protein. Dep6 exhibited strong hydrolase activity across wide ranges of pH (pH 4 to 8) and temperature (20 to 60°C) and degraded polysaccharides on the surface of STEC strain HB10. In addition, both Dep6 and PHB19 degraded biofilms formed by STEC strain HB10.

In a mouse STEC infection model, delayed Dep6 treatment (3 h postinfection) resulted in only 33% survival, compared with 83% survival when mice were treated simultaneously with infection. In comparison, pretreatment with Dep6 led to 100% survival compared with that of the control group. Surprisingly, a single PHB19 treatment resulted in 100% survival in all three treatment protocols. Moreover, a significant reduction in the levels of  proinflammatory cytokines was observed at 24 h postinfection in Dep6- or PHB19-treated mice. These results demonstrated that Dep6 or PHB19 might be used as a potential therapeutic agent to prevent STEC infection.

IMPORTANCE Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen worldwide. The Shiga-like toxin causes diarrhea, hemorrhagic colitis, and life-threatening hemolytic uremic syndrome (HUS) in humans. Although antibiotic therapy is still used for STEC infections, this approach may increase the risk of HUS. Phages or phage-derived depolymerases have been used to treat bacterial infections in animals and humans, as in the case of the “San Diego patient” treated with a phage cocktail. Here, we showed that phage PHB19 and its O91-specific polysaccharide depolymerase Dep6 degraded STEC biofilms and stripped the lipopolysaccharide (LPS) from STEC strain HB10, which was subsequently killed by serum complement in vitro. In a mouse model, PHB19 and Dep6 protected against STEC infection and caused a significant reduction in the levels of proinflammatory cytokines. This study reports the use of an O91-specific polysaccharide depolymerase for the treatment of STEC infection in mice.

 A novel tail-associated O91-specific polysaccharide depolymerase from a podophage reveals lytic efficacy of shiga toxin-producing Escherichia coli, 28 February 2020

Applied and Environmental Microbiology

Yibao Chen, Xiangmin Li, Shuang Wang, Lingyu Guan, Xinxin Li, Dayue Hu, Dongyang Gao, Jiaoyang Song, Huanchun Chen, Ping Qian

DOI: 10.1128/AEM.00145-20

https://aem.asm.org/content/86/9/e00145-20 

Lettuce is overrated: FDA’s leafy greens STEC action

I’ll say it again, as a comic in all seriousness: Lettuce is overrated.

My favorite salad is a Greek one with all those veggies and no lettuce.

The U.S. Food and Drug Administration announced last week that between 2009 and 2018, FDA and the Centers for Disease Control and Prevention (CDC) identified 40 foodborne outbreaks of Shiga toxin-producing E. coli (STEC) infections in the U.S. with a confirmed or suspected link to leafy greens.

Holy shit.

This is why The Tragically Hip were so great, and why they never appealed much beyond Canada.

I feel the same about academia.

And why Osterholm called me 15 years ago as a consultant for Fresh Express, and asked me how dare I the lettuce and skull picture, and I said because I can and it was fairly apt given there have been 40 outbreaks.

Holy shit (this is me echoing my John Oliver voice).

Coronavirus is just confirming: Go public, go often, go hard.

It’s the only way people will pay attention.

And as this story in the N.Y. Times points out, there have been spectacular public health failures by people who tell others, just shut the fuck up.

According to the FDA, it has an unwavering commitment to advancing the safety of fresh leafy greens. Leafy greens are among the most widely consumed vegetables and an important part of an overall healthy diet. While millions of servings are consumed safely every day, this produce commodity has been implicated too often in outbreaks of foodborne illness, and we believe that FDA, along with leafy greens sector stakeholders, can do more.

Between 2009 and 2018, FDA and Centers for Disease Control and Prevention (CDC) identified 40 foodborne outbreaks of Shiga toxin-producing E. coli (STEC) infections in the U.S. with a confirmed or suspected link to leafy greens. While most strains of E. coli are harmless, STEC can cause bloody diarrhea, anemia, blood-clotting problems, and kidney failure – conditions that are potentially life-threatening. The most common STEC, E. coli O157:H7, is the type most often associated with outbreaks.

Most leafy greens are grown outdoors, where they are exposed to soil, animals, and water, all of which can be a source of pathogen contamination. In addition, leafy greens are mostly consumed raw, without cooking or other processing steps to eliminate microbial hazards. The Produce Safety Rule under the FDA Food Safety Modernization Act (FSMA) sets science-based standards to help ensure that water, soil amendments (e.g., fertilizer or compost), food contact surfaces and other materials that touch produce during growing, harvesting, packing, and holding do not contribute to produce contamination. The Produce Safety Rule also addresses animal intrusion into fields and worker hygiene.

Due to the recurring nature of outbreaks associated with leafy greens, FDA has developed this commodity-specific action plan. What follows is an overview of the actions FDA plans to take in 2020 to advance work in three areas: (1) prevention, (2) response, and (3) addressing knowledge gaps.

Kansas veterinary medicine researchers develop new method to improve food safety

From a press release, as if you couldn’t tell:

Faculty members from the Kansas State University College of Veterinary Medicine have developed a faster, more efficient method of detecting “Shiga toxin-producing E. coli,” or STEC, in ground beef, which often causes recalls of ground beef and vegetables.

“The traditional gold standard STEC detection, which requires bacterial isolation and characterization, is not amenable to high-throughput settings and often requires a week to obtain a definitive result,” said Jianfa Bai, section head of molecular research and development in the Kansas State Veterinary Diagnostic Laboratory.

The new method developed by Bai and colleagues requires only a day to obtain confirmatory results using a Kansas State University-patented method with the partition-based multichannel digital polymerase chain reaction system.

“We believe the new digital polymerase chain reaction detection method developed in this study will be widely used in food safety and inspection services for the rapid detection and confirmation of STEC and other foodborne pathogens,” said Jamie Henningson, director of the Kansas State Veterinary Diagnostic Laboratory.

When ingested through foods such as ground beef and vegetables, STEC can cause illnesses with symptoms including abdominal pain and diarrhea. Some illnesses caused by STEC may lead to kidney failure and can be life-threatening.

“Some E. coli strains do not produce Shiga toxins and thus do not affect human health as much,” said Xuming Liu, research assistant professor. “Because cattle feces and ground beef can contain harmless or less pathogenic E. coli along with STEC, the most commonly used polymerase chain reaction cannot identify pathogenic E. coli strains in a complex sample matrix.”

The new digital polymerase chain reaction test was developed for research and food safety inspections that require shorter turnaround and high throughput, without sacrificing detection accuracy.

“While the current, commonly used testing method is considered to be the gold standard, it is tedious and requires many days to obtain results that adequately differentiate the bacteria,” said Gary Anderson, director of the International Animal Health and Food Safety Institute at the K-State Olathe campus.

The study, “Single cell-based digital PCR detection and association of Shiga toxin-producing E. coli serogroups and major virulence genes,” which describes the test design and results, was published in the Journal of Clinical Microbiology.

Persister, I don’t even know her: STEC in produce

Bacterial persistence is a form of phenotypic heterogeneity in which a subpopulation, persisters, has high tolerance to antibiotics and other stresses. Persisters of enteric pathogens may represent the subpopulations capable of surviving harsh environments and causing human infections. Here we examined the persister populations of several shiga toxin-producing Escherichia coli (STEC) outbreak strains under conditions relevant to leafy greens production.

The persister fraction of STEC in exponential-phase of culture varied greatly among the strains examined, ranging from 0.00003% to 0.0002% for O157:H7 strains to 0.06% and 0.08% for STEC O104:H4 strains. A much larger persister fraction (0.1–11.2%) was observed in STEC stationary cells grown in rich medium, which was comparable to the persister fractions in stationary cells grown in spinach lysates (0.6–3.6%). The highest persister fraction was measured in populations of cells incubated in field water (9.9–23.2%), in which no growth was detected for any of the STEC strains examined. Considering the high tolerance of persister cells to antimicrobial treatments and their ability to revert to normal cells, the presence of STEC persister cells in leafy greens production environments may pose a significant challenge in the development of effective control strategies to ensure the microbial safety of fresh vegetables.

Enhanced formation of shiga toxin-producing Escherichia coli persister variants in environments relevant to leafy greens production

Science Direct, Food Microbiology, Volume 84

Sandy Thao, Maria T. Brandl, Michelle Qiu Carter

https://www.sciencedirect.com/science/article/pii/S0740002018311353