Microbiologists discover how gut bacterial resources are hijacked to promote intestinal and foodborne illnesses

UT Southwestern Medical Center microbiologists have identified key bacteria in the gut whose resources are hijacked to spread harmful foodborne E. coli infections and other intestinal illnesses.

sperandio-vanessaThough many E. coli bacteria are harmless and critical to gut health, some E. coli species are harmful and can be spread through contaminated food and water, causing diarrhea and other intestinal illnesses. Among them is enterohemorrhagic E. coli or EHEC, one of the most common foodborne pathogens linked with outbreaks featured in the news, including the multistate outbreaks tied to raw sprouts and ground beef in 2014.

The UT Southwestern team discovered that EHEC uses a common gut bacterium called Bacteroides thetaiotaomicron to worsen EHEC infection. B. thetaiotaomicron is a predominant species in the gut’s microbiota, which consists of tens of trillions of microorganisms used to digest food, produce vitamins, and provide a barrier against harmful microorganisms.

“EHEC has learned to how to steal scarce resources that are made by other species in the microbiota for its own survival in the gut,” said lead author Dr. Meredith Curtis, Postdoctoral Researcher at UT Southwestern.

The research team found that B. thetaiotaomicron causes changes in the environment that promote EHEC infection, in part by enhancing EHEC colonization, according to the paper, appearing in the journal Cell Host Microbe.

e.coliO157H7“We usually think of our microbiota as a resistance barrier for pathogen colonization, but some crafty pathogens have learned how to capitalize on this role,” said Dr. Vanessa Sperandio, Professor of Microbiology and Biochemistry at UT Southwestern and senior author (left).

EHEC senses changes in sugar concentrations brought about by B. thetaiotaomicron and uses this information to turn on  virulence genes that help the infection colonize the gut, thwart recognition and killing by the host immune system, and obtain enough nutrients to survive. The group observed a similar pattern when mice were infected with their equivalent of EHEC, the gut bacterium Citrobacter rodentium. Mice whose gut microbiota consisted solely of B. thetaiotaomicron were more susceptible to infection than those that had no gut microbiota. Once again, the research group saw that B. thetaiotaomicron caused changes in the environment that promoted C. rodentium infection.

“This study opens up the door to understand how different microbiota composition among hosts may impact the course and outcome of an infection,” said Dr. Sperandio, whose lab studies how bacteria recognize the host and how this recognition might be exploited to interfere with bacterial infections. “We are testing the idea that differential gastrointestinal microbiota compositions play an important role in determining why, in an EHEC outbreak, some people only have mild diarrhea, others have bloody diarrhea and some progress to hemolytic uremic syndrome, even though all are infected with the same strain of the pathogen.”

Other UT Southwestern researchers involved in the work include Dr. Ralph DeBerardinis, Associate Professor with the Children’s Medical Center Research Institute at UT Southwestern, Eugene McDermott Center for Human Growth and Development, and Pediatrics, who holds the Joel B. Steinberg, M.D. Chair in Pediatrics and is Sowell Family Scholar in Medical Research; Dr. Zeping Hu, Assistant Professor with Children’s Medical Center Research Institute at UT Southwestern and Pediatrics; and Claire Klimko, Research Technician. The work was carried out in collaboration with researchers at Kansas State University and supported by the National Institute of Health and the Burroughs Wellcome Fund.

When STEC are your target, where do you aim?

Mick Bosilevac, Ph.D., a research microbiologist with the USDA Agricultural Research Service, U.S. Meat Animal Research Center, Meat Safety and Quality Research Unit, has a good piece about testing braylee.beaver.e.coli.O111for STECs, or shiga-toxin producing E. coli in the current Food Safety Magazine.

Those are the E. coli that make people really sick.

A few edited highlights are below, but the full piece is available at http://www.foodsafetymagazine.com/magazine-archive1/aprilmay-2013/when-stec-are-your-target-where-do-you-aim/.

Shiga toxin-producing Escherichia coli (STEC) can cause illnesses that range from diarrhea to hemorrhagic colitis and hemolytic-uremic syndrome (HUS). More than 70 serotypes of STEC have been described, and fortunately, only a handful have been associated with these severe diseases. The STEC that can cause these severe diseases are referred to as Enterohemorrhagic E. coli (EHEC). E. coli O157:H7 is the EHEC most often associated with the severest forms of disease as well as outbreaks from contact with or consumption of contaminated foods, animals and water. It should be noted that the food has historically been ground beef; the animals, cattle; and the water presumably contaminated by runoff from a cattle production facility.

Numerous non-O157 EHEC have been linked to illnesses and outbreaks of disease similar to that of E. coli O157:H7, with only one occurrence linked to beef. The U.S. Centers for Disease Control and chad.ingle.E.coliPrevention has identified the most common non-O157 EHEC and reported that just six serotypes (O26, O45, O103, O111, O121 and O145) are responsible for 71 percent of total infections from all sources. As part of its strategy to focus more on prevention, the U.S. Department of Agriculture Food Safety and Inspection Service (USDA FSIS) in the Federal Register implemented its decision to consider STEC of the six most frequent serogroup adulterants in certain beef products and began testing beef trimmings for these pathogens on June 4, 2012. In response, commercial test kit manufacturers and testing laboratories have rapidly introduced test kits and services that can detect and/or confirm the presence of the “Top Six” EHEC.

Recently, our group completed and submitted a research paper describing the strengths and weaknesses of five commercially available EHEC detection methods with comparison to the FSIS MLG and our own in-house EHEC detection and confirmation assays. In that forthcoming paper, we describe that each method, when used according to the manufacturer’s directions, was able to identify 1–3 CFU EHEC in samples ranging in size from 25 g and 65 g to 375 g. However, since many methods have their own proprietary enrichment media and enrichment conditions, it is difficult if not impossible to directly compare the same sample in a side-by-side fashion. Thus, in our study, we followed up the inoculation experiments with 500 abigal.hennessy.e.colienrichments acquired from a regional service lab and tested each by all the methods. The results of this side-by-side comparison were unexpected: 170 sample enrichments were positive by one or more of the methods used, whereas only 2 samples were identified as positive by all seven methods. Culture results from these two samples identified one containing an EHEC O26, whereas the other contained a STEC, an EPEC (Enteropathogenic E. coli that contain eae and lack stx) and an O26 E. coli. Thus, all methods identified the one sample that contained a Top Six EHEC, and all methods identified a sample containing E. coli that produced a false, potential-positive result.

Delving deeper into the range of discrepancies between methods, we found that a large portion of the difference was due to the sample preparation before PCR. Some used 20 µL of enrichment, some, 50 µL and others, 1 mL for the preparation of DNA. A greater amount of sample going into a preparation did not necessarily agree with more positive tests or greater sensitivity. In many cases, we were able to take discrepant DNA preparations from the same sample and run them through the other assays. When this was done, negative DNA preparations stayed negative and positive preparations stayed positive. No one DNA preparation could be determined to perform better, because each test method had its own unique potential-positive samples.  

Using the most extensive culture isolation protocols to confirm potential positive samples still fails to identify an EHEC much of the time. In fact, even confirming the presence of a STEC has been accomplished only at an approximate rate of 30 percent. In a 2011 study of commercial ground beef, we cultured all stx-positive enrichments. Every stx-e.coli.twins.uk.09positive enrichment was repeatedly plated to washed sheep’s blood agar and up to 50 colonies were picked and individually screened to determine if they each were a STEC. The rate of successfully isolating a STEC ranged from 10 to 50 percent, depending on the sources and batches of ground beef examined. In a more recent study, all samples identified as reactive by any of five EHEC detection methods under comparison were sent to our group for culture resolution of the results. There were 550 samples in this study: 36 were identified as reactive and 21 as potential positive by one or more of the methods. Culture isolation was able to recover two different Top Six EHEC: one from a sample identified as potential positive by all methods examined, and one from a sample that was identified as reactive by only one of the methods examined. In the second case, this was an EHEC O111 that went through all the methods undetected. Even the one method that called the sample containing this EHEC reactive failed to call the sample potential positive. This isolate must have been at a very low concentration for the PCR methods to have not adequately detected it. The culture isolation process took nearly 6 weeks to complete on these 36 enrichments, and even then with 2 samples found to contain an EHEC, 14 containing a STEC, 12 an EPEC and 5 others a generic E. coli of Top Six serotype, there were still 16 samples from which no isolates could be recovered to explain any of the PCR-detected EHEC targets. This raises the question of how useful the results of current EHEC detection methods may be without adequate culture and isolation techniques by which to assess them.

Four more cases of EHEC – E. coli O157 — in Hamburg

Aerztezeitung.de is reporting that four more cases of enterohaemorrhagic Escherichia coli (EHEC) have emerged in Hamburg, Germany, following the death of a 6-year-old girl last week.

An 11-year-old boy and a 3-year-old kindergartner tested positive earlier this week, and two women aged between 68 and 88 years were earlier diagnosed with EHEC. Tests have identified the strain as E. coli O157.

Six-year-old girl dies from E. coli in Germany

The translation is rough and details sketchy, but Focus is reporting a 6-year-old girl from Hamburg died over the weekend from the effects of EHEC, which probably means some strain of shiga-toxin producing E. coli.

A spokesman for the Health Authority of the City of confirming the news agency on Sunday evening, a case of illness with the pathogen.According to the newspaper "Die Welt" on Monday, the child died in the early hours of Sunday. The first grader had shown since the beginning of last week, symptoms of infection with the aggressive food germ, the head of a primary school in Hamburg-Blankenese said on Sunday. She was treated at a hospital. Apparently it was an isolated case

"This is an isolated incident," said the spokesman. "It is not at all comparable to the situation last year" (meaning sprouts and E. coli O104, in which 53 people died).

Most German E. coli-in-sprouts patients have recovered well, except for the 50 who died

 Maybe something was lost in translation, but Prof. Christian Gerloff, Head of Neurology at the Hamburg-Eppendorf University Hospital (UKE), told the annual congress of the German Society for Neurology in Wiesbade on Sept. 28, 2011, that despite their life-threatening infection, most E. coli O104-in-raw-sprouts patients have recovered well from the summer’s epidemic.

The professor described how the wave of illness, caused by contaminated bean sprouts, was new territory for neurology. The neurology department had to help "in the crisis management of an epidemic for the first time."

According to the Robert Koch Institute, almost 3,500 EHEC cases were registered in Germany between May and July 2011. 50 patients, who were infected with the aggressive intestinal germ, died of the disease.

Gerloff stated that, of the around 100 patients who were treated for the most intense course of the disease, only three are still displaying symptoms, such as paralysis or lalopathy. He explained that everyone else has recovered very well.

In each case, the illness began with diarrhea. However, every third patient was also hit by a life-threatening kidney failure –hemolytic-uremic syndrome (HUS). In addition, every sixth patient developed acute neurological disorders; in some cases seizures, in other cases epileptic fits, said Gerloff. "Patients fell into a coma within a few days."

Gerloff also reported that some EHEC cases resulted in neurological disorders without HUS. As such, the disorders do not always relate to the kidney failure.

Best in show: dog show leads to E. coli outbreak in Sweden

Around 50 dog owners and several dogs are believed to have been infected with enterohaemorrhagic E. coli (EHEC) following a dog show in eastern Sweden.

"We’re right in the middle of investigating where the bacteria came from," Britt Åkerlind of the infectious disease unit of Östergötland County told The Local.

So far, two Swedes have been confirmed as infected by EHEC, one from Skåne in the south, and another from Gothenburg in the west.

"But we’re expecting more confirmed cases to come in," said Åkerlind.

Those infected with the bacteria all attended a dog show near Norrköping in eastern Sweden held the first weekend in June.

Of the roughly 120 participants, who traveled from all over Sweden as well as from Denmark, Norway, and Finland, about half have come down with symptoms stemming from EHEC infection.

"We’ve also received reports that some of the dogs have had upset stomachs," said Åkerlind, who labeled the outbreak as "quite large."

EHEC on Dutch beetroot sprouts not same strain as in Germany

Look for something and it will be found.

But is anyone else concerned about the E. coli being found on European produce, even if it is not the O104 outbreak strain?

EU officials said on Wednesday evening traces of EHEC bacteria have been found on beetroot sprouts from a Dutch grower.

The sprouts are not carrying the same variant of the bacteria as has killed some 27 people in Germany, but all produce from that grower is being removed from the supermarket shelves as a precautionary measure.

Beetroot sprouts are sprouted beetroot seeds which can be eaten in salads or used as decoration.

3 dead in German E. coli outbreak; more than 400 sick

The food safety news from Germany continues to be disturbing. Below is a translation of a German article, so excuse any inaccuracies.

The killer germ called EHEC now appeared three lives: In Lower Saxony (Diepholz) passed away a woman (83). She was admitted nine days ago because of bloody diarrhea hospitalized and treated in hospital. The laboratory evidence of EHEC infection was positive. The woman died on Saturday. Investigations by the health department in the immediate death Diepholz also ongoing.

Meanwhile it was announced that a woman possibly died (25) to EHEC in Bremen. The young woman had shown the symptoms of EHEC pathogen, such as the Bremen health authority said. The EHEC pathogens had not been demonstrated so laboratory diagnosis. In Schleswig-Holstein, died in a 80-year-old woman infected. Whether the pathogen was the cause of death is still unclear.

In their search for the source of the infections with the dangerous intestinal bacteria EHEC is making the Frankfurt FDA. All 19 previously in the Main metropolis ill have eaten in the same canteen, a Frankfurt-based consultancy, said Bellinger Oswald from the Health Department. Two canteens of PWC Consulting had been closed on Monday as a precaution.

The fault is probably a loaded delivery to the canteen: "We assume that the source of infection is located in Northern Germany," said Bellinger. Currently, experts evaluated the delivery notes of the two affected canteens. "We still believe that the transfer has taken place through raw food." Safety reasons are investigated and the kitchen staff, results of samples are expected by the end of the week. As long as the canteens were closed.

More than 40 of these patients also suffered under the hemolytic-uremic syndrome (HUS), which is caused by the intestinal bacteria.

E. coli outbreak spreading in Germany; 80 sick, dozens hospitalized

Two victims of a potentially fatal strain of E. coli have been placed on artificial respiration machines, a Frankfurt hospital said Monday, while hospitals across Germany were reporting a surge in infections.

German media report that EHEC, or Enterohaemorrhagic Escherichia coli, is a virulent strain of gut bacterium which can cause stomach cramps and diarrhea, and can lead to anaemia and kidney damage.

The strain of E. coli is not specified in media reports, but the kidney failure bit makes it sound like a Shiga-toxin producing E. coli.

In Frankfurt, 10 people had been hospitalized, of whom four were in intensive care, while a further 50 people were ill with mild symptoms of EHEC.

A total of 40 people were being treated in Hamburg, most of whom were female, the city’s health authorities said.

Around 800 to 1,200 cases of EHEC are recorded in Germany each year, predominantly affecting children. The current outbreak is unusual for causing severe symptoms in adults, primarily women.

The bacterium is commonly transmitted through contaminated raw or undercooked ground meat products or milk, but disease experts said there was evidence that uncooked vegetables might have helped to spread the latest outbreak.

Gerard Krause of the Robert Koch health authority responsible for epidemiology, said,

“Women prepare food more often, and it is there they could have come into contact with it, possibly while cleaning vegetables or other foodstuffs.”

In a German version of blame-the-consumer, the Robert Koch Institute has recommended people improve kitchen hygiene, making sure in particular that cutting boards and knives are clean.

It’s doubtful that all 80 sick people practiced lousy kitchen cleanliness at the same time across Germany.