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.
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.
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.
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.These people must be hospitalized to monitor kidney function and for supportive therapy. It can take a few weeks to recover from HUS, and some people suffer permanent damage or even die. You might be surprised that treatment does not include antibiotics.
This is because there is no evidence that antibiotics help with the disease and their use can increase the odds of developing HUS. Even after recovery, patients can continue to shed O157:H7 in their feces for several weeks up to several months.
The main reservoir for O157:H7 is the cow intestinal tract, explaining why some of the first outbreaks were associated with beef products. However, over the years, outbreaks have been associated with a wide variety of food products, including various frozen foods, spinach, alfalfa sprouts, radishes, bologna, hazelnuts and cookie dough. It is even possible to acquire O157:H7 from contaminated water used for drinking and swimming.
In many cases, unless the health department investigates an outbreak, the source of the infecting E. coli is never conclusively determined.There are some things you can do to protect against getting O157:H7, with a major focus on food handling. You should always wash fruits and vegetables and thoroughly cook meat products. You should also avoid drinking untreated water.
But the protections in place against E. coli are much larger than just an individual thoroughly cooking their hamburger.In the United States, there are recommended best practices for large-scale farming of fruits, vegetables and meat that promote hygienic practices and reduce cross-contamination. In addition, some ground beef products are routinely irradiated to protect consumers.
The Latest Outbreak
You might be wondering how you can learn more about E. coli O157:H7 outbreaks. The Centers for Disease Control and Prevention maintain a database listing all documented foodborne illness outbreaks, along with how many people were affected and the source of the contamination, if it’s known.
The latest outbreak of E. coli O157:H7 occurred in the fall of 2012, infecting 33 people across 5 states. Fortunately, there were no deaths.The contamination was traced to batches of organic spinach and spring mix greens being sold in supermarkets throughout the Northeastern United States. This just goes to show you that the hamburgers are not the only culprits!
E. coli O157:H7 infects the human colon and produces Shiga toxin. The Shiga toxin damages the lining of the colon, causing hemorrhaging and diarrhea.
It can then pass into the bloodstream and travel throughout the body. This can result in hemolytic uremic syndrome, or HUS, which is characterized by hemolytic anemia, thrombocytopenia and kidney failure.The primary treatment for E.
coli O157:H7 is supportive therapy; antibiotic use is discouraged. Infections are diagnosed by culturing, serological and molecular methods, although rarely are individual infections traced back to the original infection source. You can protect yourself from E.
coli infection by using good personal hygiene and thoroughly cooking food. To keep up with the latest E. coli O157:H7 outbreaks, visit the CDC’s website, where you can learn more about the extent of outbreaks and their source.