E. coli persisters

Escherichia coli O157:H7 (EcO157) infections have been recurrently associated with produce. The physiological state of EcO157 cells surviving the many stresses encountered on plants is poorly understood. EcO157 populations on plants in the field generally follow a biphasic decay in which small subpopulations survive over longer periods of time. We hypothesized that these subpopulations include persister cells, known as cells in a transient dormant state that arise through phenotypic variation in a clonal population.

Using three experimental regimes (with growing, stationary at carrying capacity, and decaying populations), we measured the persister cell fractions in culturable EcO157 populations after inoculation onto lettuce plants in the laboratory. The greatest average persister cell fractions on the leaves within each regime were 0.015, 0.095, and 0.221%, respectively. The declining EcO157 populations on plants incubated under dry conditions showed the largest increase in the persister fraction (46.9-fold). Differential equation models were built to describe the average temporal dynamics of EcO157 normal and persister cell populations after inoculation onto plants maintained under low relative humidity, resulting in switch rates from a normal cell to a persister cell of 7.7 × 10−6 to 2.8 × 10−5 h−1. Applying our model equations from the decay regime, we estimated model parameters for four published field trials of EcO157 survival on lettuce and obtained switch rates similar to those obtained in our study. Hence, our model has relevance to the survival of this human pathogen on lettuce plants in the field. Given the low metabolic state of persister cells, which may protect them from sanitization treatments, these cells are important to consider in the microbial decontamination of produce.

IMPORTANCE Despite causing outbreaks of foodborne illness linked to lettuce consumption, E. coli O157:H7 (EcO157) declines rapidly when applied onto plants in the field, and few cells survive over prolonged periods of time. We hypothesized that these cells are persisters, which are in a dormant state and which arise naturally in bacterial populations. When lettuce plants were inoculated with EcO157 in the laboratory, the greatest persister fraction in the population was observed during population decline on dry leaf surfaces. Using mathematical modeling, we calculated the switch rate from an EcO157 normal to persister cell on dry lettuce plants based on our laboratory data. The model was applied to published studies in which lettuce was inoculated with EcO157 in the field, and switch rates similar to those obtained in our study were obtained. Our results contribute important new knowledge about the physiology of this virulent pathogen on plants to be considered to enhance produce safety.

Formation of Escherichia coli O157:H7 persister cells in the lettuce phyllosphere and application of differential equation models to predict their prevalence on lettuce plants in the field

08 November 2019

Applied and Environmental Microbiology

Daniel S. Munther, Michelle Q. Carter, Claude V. Aldric, Renata Ivanek, Maria T. Brandl

DOI: 10.1128/AEM.01602-19

https://aem.asm.org/content/86/2/e01602-19.abstract?etoc

As romaine problems continue, US FDA takes closer look

Chris Koger of The Packer writes the U.S. Food and Drug Administration will be collecting romaine samples in California and Arizona for a year to test for salmonella and E. coli following several foodborne outbreaks linked to the lettuce.

The new program begins this month, according to the FDA, citing two E. coli outbreaks in 2018 linked to romaine, and another one in October that was suspected to be from the leafy green. In its notice on the surveillance program, the FDA also cited a 2012 Salmonella Newport outbreak from romaine.

“Consistent with the FDA’s mission to protect consumers, if one of the target pathogens is detected as a result of this assignment, the agency will perform whole genome sequencing of the microorganism’s DNA to determine its virulence and whether it is genetically related to isolates causing human illness,” according to the notice.

 All samples will be tested before processing to allow the FDA to quickly find the point of origin, which has been problematic in recent outbreaks as public and federal health agencies traced lettuce through the supply chain. In part, traceability hurdles have led to the FDA’s New Era of Smarter Food Safety program, which tasks the industry with enhancing traceability methods and technology.

Trimmed and washed lettuce will be tested, but not fresh-cut lettuce, and no lettuce at the farm-level will be involved in the surveillance program.

Samples will be targeted at facilities and farms identified in the outbreaks starting in 2017, including wholesalers, foodservice distribution centers, and commercial cooling and cold storage facilities, according to the FDA notice.

Lettuce continues to be overrated: 7 sick in Maryland from E. coli linked to pre-packaged salad

The Maryland Department of Health says seven confirmed cases of E. coli infections have been linked to pre-packaged Caesar salads.

According to the department of health, the infections were identified in people who’d eaten Ready Pac Bistro Bowl Chicken Caesar Salad purchased at Sam’s Club stores in Maryland.

One person was hospitalized as a result of the E. coli O157 infection.

No deaths have been linked to it.

And there aren’t enough bagpipes and mandolins in rock.

At least 30 sickened: Multistate outbreak of listeriosis associated with packaged leafy green salads, United States and Canada, 2015-2016

We investigated an outbreak of listeriosis detected by whole-genome multilocus sequence typing and associated with packaged leafy green salads. Nineteen cases were identified in the United States during July 5, 2015–January 31, 2016; isolates from case-patients were closely related (median difference 3 alleles, range 0–16 alleles). Of 16 case-patients interviewed, all reported salad consumption. Of 9 case-patients who recalled brand information, all reported brands processed at a common US facility.

The Public Health Agency of Canada simultaneously investigated 14 cases of listeriosis associated with this outbreak. Isolates from the processing facility, packaged leafy green salads, and 9 case-patients from Canada were closely related to US clinical isolates (median difference 3 alleles, range 0–16 alleles). This investigation led to a recall of packaged leafy green salads made at the processing facility. Additional research is needed to identify best practices and effective policies to reduce the likelihood of Listeria monocytogenes contamination of fresh produce.

CDC

Julie L Self, Amanda Conrad, et al

https://wwwnc.cdc.gov/eid/article/25/8/18-0761_article?deliveryName=DM4960

Ontario parents speak out after 2-year-old’s E. coli linked death

I seemed to have missed this, which is inexcusable, volunteer or not, medical stuff for me or not, but here it is, a month later (and if I did publish it, shows where my brain is going).

Avis Favaro of CTV News reported in early May that it all started with a romaine salad.

Kristen and Brad Bell felt a little sick after eating the salad last October.

Their two-year-old son soon started to show more severe symptoms. Cooper Bell was vomiting. He developed diarrhea. Then his mother noticed the blood in his diaper.

“I had no idea [what] was happening,” Kristen Bell told CTV News from her home in Stirling, Ont.

“I thought ‘This is not normal.'”

An emergency room doctor thought Cooper might have contracted a bacterial infection. The family’s pediatrician agreed, saying the Bells should keep their son hydrated and bring him back in the morning.

Soon after the Bells returned home, they noticed some worrying changes in Cooper’s behavior.

“He wasn’t responding to me the same as he was earlier. It wasn’t long after that, that he had a seizure in Brad’s arms,” Kristen Bell said.

Seeing their son shaking uncontrollably with his eyes closed, the Bells called an ambulance. He spent a few hours in hospital in nearby Belleville, Ont., and was then airlifted to the Children’s Hospital of Eastern Ontario in Ottawa.

Doctors at CHEO diagnosed Cooper with kidney failure brought on by E. coli. He suffered cardiac arrest and died. The Bells believe it was the romaine lettuce that made Cooper sick, although they were unable to send the lettuce for testing to confirm their belief because it had been thrown out.

There were 29 illnesses and 10 hospitalizations reported across Canada during last fall’s E. coli outbreak, according to the Public Health Agency of Canada. It was one of three outbreaks in North America over the past year all of which were linked to romaine lettuce.

Keith Warriner, a food safety expert and professor at the University of Guelph in Ontario, said in an interview that the food industry has long been slow to improve its testing practices something that could improve overall food safety, but would mean extra costs for their operations.

“The industry itself has known for many years what it needs to do, but it’s just been reluctant to do it,” he said.

The Bells agree. They’re sharing their story of grief with the hope it will help hospital workers and other parents better understand the danger of E. coli, but also because they want to see changes at the food production level.

“E. coli shouldn’t be in our food,” Brad Bell said.

“The way that we’re growing food is dangerous, and something has to change.”

Can you hear me know? The new holiday tradition: Searching for recalls and outbreak information

Longtime friend of the barfblog.com, Michéle Samarya-Timm, health educator at the Somerset County Department of Health (that’s in New Jersey, represent) writes:

Baking pumpkin pies with Aunt Kay’s secret recipe.  Watching Miracle on 34th Street.  Preparing the dining room with the good china.  Diffusing political conversations at the dinner table. 

Some traditions give a sense of warmth, connection, and continuity, and regularly define a family’s holiday. Unfortunately, there is now a need to add an additional tradition to the season – actively checking for foodborne outbreaks and recalls to prevent folks from getting sick.

 Last week, on Tuesday, November 20th at 2pm, (two days before Thanksgiving), the CDC posted a media statement with advice to consumers, restaurants, and retailers: 

 “CDC is advising that U.S. consumers not eat any romaine lettuce, and retailers and restaurants not serve or sell any, until we learn more about the outbreak.”

 The need to release such a notice, right before a major holiday is an unpropitious scenario.  It was also very concerning in its specificity to consumers, retailers and restaurants:

“Wash and sanitize drawers or shelves in refrigerators where romaine was stored.”

Such an alert is most effective if it reaches the intended audiences.   Folks at my holiday table did not hear about the outbreak.  Neither did many local health departments.

Issuing media releases is one way for public health agencies to reach large groups of people. However, distracted by holiday preparations, travel, shopping, family, football and bad weather this advisory was only partially disseminated to the public. A person had to be following news outlets or social media to receive timely notice. I heard about the recall from the woman next to me while I was getting a haircut – not from the CDC or FDA, or any other federal or state agency.   

 It’s disturbing. The CDC could have sent this info directly to local health departments, or notify them that a news release was issued. This was not the first time as a local public health official that I received delayed – or no – official communication about a national foodborne issue.

Local public health professionals rely on communications systems established by federal and state oversight agencies. Most commonly, if a verified or suspect foodborne contamination or outbreak has occurred, the Centers for Disease Control and Prevention (CDC), the U.S. Department of Agriculture, or the U.S. Food and Drug Administration (FDA) will ascertain the appropriateness of information release. If this information is deemed credible, notification is forwarded individually or en masse to state departments of health. The states, in turn, push this information down to local regulators. Each step in the process contains elements that may delay the rapid dissemination of outbreak information. The ability and willingness of all stakeholders to quickly and readily share incident particulars with fellow responding agencies can enhance effectiveness and amplify response efforts.

Electronically sending this advisory directly to the nearly 3,000 local health departments in the US would provide the opportunity for hundreds of health inspectors, health educators, epidemiologists and other to reach the hospitals, food banks, schools, mom and pop establishments and local residents who may not have otherwise received the alert. This was a missed opportunity, and hopefully one that didn’t cause additional cases of illness.

As I’ve written before, coordinated communication strategies within and between public health agencies is less robust than it should be. As a result, state and local public health officials may hear about foodborne disease issues first from other sources, such as the media, word of mouth, public complaints, or the food industry.   

 We need to learn how to communicate better with each other.  Local public health shouldn’t have to keep an eye on the news media, Twitter or Facebook for information pertinent to protecting the people in our jurisdictions.  A multitude of electronic portals exist for purposes of interagency  communication, CDC, FDA, and the public health system should collectively define how pertinent information – such as this romaine advisory – rapidly and routinely gets to the grass roots public health workforce. Continuously improving interagency coordination and communication is a goal that is fundamental to increasing the effectiveness of this nation’s food safety systems. I’m putting this out there, because I’m willing to help with the solution. That way, in future years, I can spend my holidays perfecting Aunt Kay’s pie recipe.

This holiday, I’m thankful for public health influencers and amplifiers – like barfblog.com – that act as outbreak aggregators, and push out info to local public health types like me.   

Some background information and recommendations on this topic can be found in:  Getting the message across: an analysis of foodborne outbreak communications between federal, state, and local health agencies   https://calhoun.nps.edu/handle/10945/49379

FDA’s Gottlieb says Romaine likely came from California (other regions might be off the hook)

Scott Gottlieb, FDA Commissioner took to the Twitter this morning while many were buying TVs and Himalayan salt lamps to talk about the Romaine-linked E. coli O157 outbreak.

I imagine there’s lots of pressure out there to lift the blanket statement from CDC to avoid all Romaine. Especially if the dates of harvest/transition from one location to another make it so it’s not likely that lettuce from certain regions would be linked to the outbreak.

Some sort of identification is great – because how would a consumer know what to ask about or how to figure out the source without it.

 

 

Lettuce is overrated: STEC in Finland

Escherichia coli are Gram-negative rod-shaped bacteria and part of the normal bacterial flora in the gastrointestinal tract, while diarrhoeagenic E. colipathotypes such as Shiga toxin-producing E. coli (STEC) and enteropathogenic E. coli (EPEC) are able to cause gastrointestinal infections [1]. STEC can lead to a severe disease, such as haemolytic-uraemic syndrome (HUS) [2]. The risk of HUS has been related especially to children under 5 years and to elderly people. HUS is characterised by acute onset of microangiopathic haemolytic anaemia, renal injury and low platelet count.

More than 400 STEC serotypes have been recognised, of which the best-known serotype is O157:H7 [1]. The most common non-O157:H7 serotypes causing human infections are O26, O103, O111 and O145 [3]. The virulence of STEC is largely based on the production of Shiga toxin 1 or 2 and is identified by detecting the presence of stx1 or stx2 genes [1,4]. The virulence of EPEC is caused by its capability to form attaching and effacing (A/E) lesions in the small intestine. This capability requires the presence of virulence genes called the locus of enterocyte effacement (LEE) in a pathogenity island (PAI) that encodes intimin [4]. Unlike STEC, EPEC do not produce Shiga toxin. EPEC are divided into two distinct groups by the presence of EPEC adherence factor plasmid (pEAF) expressing bundle-forming pili (BFP), which is a virulence determinant of typical EPEC (tEPEC) [5]. Thus atypical EPEC (aEPEC) are defined as E. coli that produce A/E lesions but do not express BFP. Typical EPEC are best known as a cause of infantile diarrhoea, especially in developing countries [6]. Diarrhoea-causing aEPEC have been shown to be separate group without a close relation to tEPEC, but some serotypes are genetically related to STEC [5]. The pathogenity of aEPEC has been questioned but their involvement with diarrhoeal outbreaks supports the idea that certain strains are diarrhoeagenic [1,7].

Both STEC and EPEC are transmitted through the faecal-oral route, and outbreaks caused by STEC and aEPEC have been described after ingestion of contaminated food or water [7,8]. STEC is common in ruminants and can be found in foods contaminated by ruminant faeces [9]. Most studies on STEC have focused on the serotype O157:H7, but infections and outbreaks caused by non-O157 strains are increasingly reported in Europe and elsewhere [1013]. Atypical EPEC strains are found in animals used for food production, such as cattle, sheep, goat, pig and poultry, in contrast to tEPEC that has been found only in humans [1,14].

Since 1995, clinicians and clinical microbiology laboratories have been obliged to report culture-confirmed STEC infections to the Finnish Infectious Disease Registry (FIDR) maintained by the National Institute for Health and Welfare (THL) in Finland. EPEC infections are not reportable. Since PCR instead of culture became the standard for screening of diarrhoeal patients in 2013, the incidence of reported STEC infections has increased in Finland to 1.2–1.8 per 100,000 population between 2013 and 2015 compared with 0.2–0.6 per 100,000 between 2000 and 2012. From 1997 to 2015, six food- or waterborne STEC outbreaks were detected in Finland (Table 1).

Outbreak of multiple strains of non-O157 Shiga toxin-producing and enteropathogenic Escherichia coli associated with rocket salad, Finland, autumn 2016

15.may.18

Eurosurvelliance, Volume 23, Issue 35, https://doi.org/10.2807/1560-7917.ES.2018.23.35.1700666

Sohvi KinnulaKaisa HemminkiHannele KotilainenEeva RuotsalainenEveliina Tarkka,Saara SalmenlinnaSaija HallanvuoElina LeinonenOllgren JukkaRuska Rimhanen-Finne

https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2018.23.35.170066