Food Poisoning: Shiga Toxin-Producing E. coli


Professor Dave here, let’s tackle food poisoning. We’ve all had it, and it’s the worst. Stomach cramps, diarrhea, nausea, not being
able to keep any food down, maybe a fever… these are all symptoms of food poisoning,
which means the consumption of contaminated food or drink. When it comes to stomach trouble, it’s not
always easy to identify what in particular is causing the symptoms. The term “gastroenteritis” refers to inflammation
of the lining of the gut, particularly the stomach and intestines, and cases of gastroenteritis
can be caused by viruses, bacteria, or parasites. When it’s clear, or at least likely, that
the source of an infection is contaminated food, we call it food poisoning. Let’s go in for a closer look. It turns out that most cases of food poisoning
clear up on their own without any type of treatment required. However, one of the most serious complications
of food poisoning is dehydration, which can be especially deadly for those that are very
young or very old. While food poisoning can be caused by a variety
of pathogens, including Staphylococcus aureus, Clostridium, Norovirus, Salmonella, Listeria,
Vibrio, or Campylobacter, today we’re going to talk about one notorious cause of food
poisoning in particular, the one you usually hear about in the news: Shiga toxin-producing
E. coli, or STEC. E. coli consists of a diverse group of bacteria
belonging to the Enterobacteriaceae family, which are associated with diseases ranging
from UTIs to respiratory illness to meningitis. Pathogenic strains of E. coli can be categorized
into what are called “pathotypes.” In particular, there are six pathotypes associated
with diarrhea, which are appropriately named “diarrheagenic E. coli.” These are: Shiga toxin-producing E. coli,
or STEC. Enterotoxigenic E. coli, or ETEC. Enteropathogenic E. coli, or EPEC. Enteroaggregative E. coli, or EAEC. Enteroinvasive E. coli, or EIEC, and diffusely
adherent E. coli, or DAEC. These bacteria are gram-negative. They’re facultative anaerobic rods, which
means they can survive both with or without oxygen present, and they contain lipopolysaccharide. The Shiga toxin-producing E. coli cause disease
by producing a toxin called Shiga toxin, and here’s where it gets more confusing. Shiga toxin-producing E. coli are sometimes
also called verocytotoxic E. coli, or VTEC, or enterohemorrhagic E. coli, or EHEC. In the United States, the most common serotype
of STEC is E. coli O157:H7, which is the type they’re usually talking about on the news,
like when there’s a widespread romaine lettuce recall. An infection begins when you swallow STEC,
meaning that you’ve gotten a microscopic amount of human or animal feces in your mouth. That may sound gross, but it happens a lot
more than you think. Common sources include raw milk, contaminated
water, or contaminated food. Foods that are considered high risk for E.
coli O157 include unpasteurized apple cider, soft cheeses made from raw milk, and sometimes
undercooked beef or contaminated lettuce. However, sometimes people get infected by
touching surfaces at petting zoos, swallowing lake water while swimming, or eating food
prepared by someone who didn’t wash their hands after using the bathroom. In most cases, STEC infections have an incubation
time of 3 to 4 days before symptoms set in. STEC strains, as their name suggests, express
a Shiga toxin that is one of the most potent bacterial toxins known. Shiga toxins consist of two major subunits,
A and B, which work together to damage cells in the gut. In particular, these toxins disrupt protein
synthesis in healthy cells and cause destruction of intestinal microvilli, which are fingerlike
projections that typically help healthy cells absorb nutrients. As a result, approximately half of patients
experience vomiting, and a significant portion experience bloody diarrhea and severe abdominal pain. In some cases, Shiga toxin can trigger an
overreaction of the immune system to attack healthy cells, as well. For the most part, STEC infections are diagnosed
by testing stool specimens in the lab. In the case of big outbreaks, identifying
the specific strain of STEC is important, so that we can track when and where each strain
was found, and where it might be spreading. Public health officials suggest that anyone
experiencing diarrhea for more than three days, especially if accompanied by vomiting
and high fever, contact their healthcare provider to get checked out. Hydration is the most important treatment,
as antibiotics are not typically prescribed for this kind of infection. In fact, antibiotics can make the illness
worse, causing patients to be at higher risk for hemolytic uremic syndrome, or HUS. HUS is a complication for a small subset of
patients that can cause renal failure and other deadly symptoms. Ultimately, the best thing you can do is wash
your hands often, be careful about what you’re eating, make sure to cook meat thoroughly
and avoid raw or unpasteurized milk or dairy products, do your best to avoid swallowing
lake or pool water, and make sure to keep food preparation areas immaculately clean. With any luck, you can avoid food poisoning for good.

16 thoughts on “Food Poisoning: Shiga Toxin-Producing E. coli

  1. Do you know of any type of food poisoning that has an effect the same day or does it all take at least 24 hours to show symptoms, i’ve heard people say that they got food poisoning from something that they ate the same day, my understanding was that all bacteria’s that causes food poisoning took at least 24 hours to show symptoms. Thanks for the information.

  2. Can anyone explain me why F has positive oxidation state in Hypoflorous acid(HOF). Despite being the most electronegative element in long form of periodic table.

  3. I'm British and I've never had food poisoning neither has any of my family… I've only ever heard of it when people go abroad

  4. Good vid. But, why do you pronounce it "E' coli", when I've always heard "e KO' li"? (Checked Websters and Youtube pronunciations too.)

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