E. coli O157:H7 - Diagnosis, Treatment & Prevention

E. coli O157:H7 - Diagnosis, Treatment & Prevention
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  • 0:07 E. coli 0157:H7 Outbreaks
  • 1:53 Diagnosis
  • 3:26 Treatment
  • 4:38 Prevention
  • 5:52 The Latest Outbreak
  • 6:34 Lesson Summary
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Lesson Transcript
Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

E. coli O157:H7 is one of the most infamous causes of foodborne illness. In this lesson, we will discuss the diagnosis, treatment, and prevention of E. coli O157:H7.

E. coli O157:H7 Outbreaks

When you hear a news report detailing an outbreak of E. coli or the recall of food products contaminated by E. coli, the majority of the time the E. coli in question is the specific serotype known as O157:H7. E. coli O157:H7 is the most common cause of E. coli infections in North America, and most outbreaks occur when food supplies are contaminated.

The O157:H7 serotype was thrust into the spotlight when a batch of contaminated ground beef patties resulted in one of the largest and most deadly foodborne illness outbreaks in U.S. history. In some O157:H7 outbreaks, the mass production and distribution of contaminated food products has resulted in geographically widespread outbreaks covering multiple states. In this lesson, we will discuss how O157:H7 is diagnosed and treated and the various measures that have been put in place to prevent future outbreaks.

But first, we need to understand a little bit about the actual disease process. After consumption of E. coli O157:H7 cells, the cells pass through the gastrointestinal tract until they reach the colon. Once in the colon, the cells bind to the intestinal walls, where they begin growing and dividing. During this time, they produce a variety of toxic proteins, including the exotoxin known as Shiga toxin.

The Shiga toxin is responsible for much of the disease symptoms associated with O157:H7, including diarrhea and intestinal hemorrhaging. In severe cases, Shiga toxin travels through the bloodstream to the kidneys, where it causes hemolytic uremic syndrome, known as HUS, which is a combination of kidney failure, low platelet counts and anemia.

Diagnosis

Depending on the severity of the symptoms, some infected people will seek treatment while others will likely endure and recover from the disease without complications. For those that seek treatment, medical professionals and public health officials have a well-defined action plan for diagnosing infection by E. coli O157:H7. Since many of the O157:H7 outbreaks are widespread, officials closely monitor all O157:H7 infections so they can act swiftly to limit the outbreak through public awareness and food recalls, if necessary.

For the individual patient, first, the patient's history is examined to determine the potential source of the infection. Many gastrointestinal illnesses have symptoms in common, like vomiting and diarrhea, so it is not always simple to determine what organism might be causing the illness. Infections are usually diagnosed through examination of the patient's feces. Feces can be cultured using media to specifically detect O157:H7. If O157:H7 is detected by culture, the culture is sent to a state or local public health lab for further characterization by serological and molecular methods.

Sometimes, if a patient has HUS, the E. coli are difficult to detect by culturing from the feces. In this case, if O157:H7 is suspected, samples can be sent to public health labs, like the Centers for Disease Control and Prevention, where more advanced techniques will be used to detect O157:H7.

Treatment

People of any age can be infected, but young children and the elderly are more likely to develop severe symptoms, like hemolytic uremic syndrome. For most otherwise-healthy people, the primary symptoms are cramps, diarrhea and vomiting, and most of these people get better within 5-7 days with supportive therapy, meaning rest and rehydration. Of those infected by E. coli O157:H7, 5-10% will develop hemolytic uremic syndrome. For people that develop HUS, symptoms are more severe and are accompanied by decreased urination, extreme fatigue and loss of healthy pink coloration in the mouth and eyelids.

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