Dr. Brian M. Kirsh, MD
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Bacteria and Foodborne Illness

What are foodborne illnesses?

Foodborne illnesses are caused by eating food or drinking beverages contaminated with bacteria, parasites, or viruses. Harmful chemicals can also cause foodborne illnesses if they have contaminated food during harvesting or processing. Foodborne illnesses can cause symptoms that range from an upset stomach to more serious symptoms, including diarrhea, fever, vomiting, abdominal cramps, and dehydration. Most foodborne infections are undiagnosed and unreported, though the Centers for Disease Control and Prevention estimates that every year about 76 million people in the United States become ill from pathogens, or disease-causing substances, in food. Of these people, about 5,000 die.
 

What causes of foodborne illnesses?

Harmful bacteria are the most common cause of foodborne illnesses. Some bacteria may be present on foods when you purchase them. Raw foods are the most common source of foodborne illnesses because they are not sterile; examples include raw meat and poultry that may have become contaminated during slaughter. Seafood may become contaminated during harvest or through processing. One in 10,000 eggs may be contaminated with Salmonella inside the egg shell. Produce such as spinach, lettuce, tomatoes, sprouts, and melons can become contaminated with Salmonella, Shigella, or Escherichia coli (E. coli) O157:H7. Contamination can occur during growing, harvesting, processing, storing, shipping, or final preparation. Sources of produce contamination are varied as these foods are grown in soil and can become contaminated during growth or through processing and distribution. Contamination may also occur during food preparation in a restaurant or a home kitchen. The most common form of contamination from handled foods is the Norwalk-like virus.

When food is cooked and left out for more than 2 hours at room temperature, bacteria can multiply quickly. Most bacteria grow undetected because they don’t produce a bad odor or change the color or texture of the food. Freezing food slows or stops bacteria’s growth but does not destroy the bacteria. The microbes can become reactivated when the food is thawed. Refrigeration also can slow the growth of some bacteria. Thorough cooking is needed to destroy the bacteria.
 

What are the symptoms of foodborne illnesses?

In most cases of foodborne illnesses, symptoms resemble intestinal flu and may last a few hours or even several days. Symptoms can range from mild to serious and include
  • abdominal cramps
  • nausea
  • vomiting
  • diarrhea, which is sometimes bloody
  • fever
  • dehydration

What are the risk factors of foodborne illnesses?

Some people are at greater risk for bacterial infections because of their age or an unhealthy immune system. Young children, pregnant women and their fetuses, and older adults are at greatest risk.
 

What are the complications of foodborne illnesses?

Some micro-organisms, such as Listeria monocytogenes and Clostridium botulinum, cause far more serious symptoms than vomiting and diarrhea. They can cause spontaneous abortion or death.
In some people, especially children, hemolytic uremic syndrome (HUS) can result from infection by a particular strain of bacteria, E. coli O157:H7 and can lead to kidney failure and death. HUS is a rare disorder that affects primarily children between the ages of 1 and 10 years and is the leading cause of acute renal failure in previously healthy children. A child may become infected after consuming contaminated food or beverages, such as meat, especially undercooked ground beef; unpasteurized juices; contaminated water; or through contact with an infected person.

The most common symptoms of HUS infection are vomiting, abdominal pain, and diarrhea, which may be bloody. In 5 to 10 percent of cases, HUS develops about 5 to 10 days after the onset of illness. This disease may last from 1 to 15 days and is fatal in 3 to 5 percent of cases. Other symptoms of HUS include fever, lethargy or sluggishness, irritability, and paleness or pallor. In about half the cases, the disease progresses until it causes acute renal failure, which means the kidneys,are unable to remove waste products from the blood and excrete them into the urine. A decrease in circulating red blood cells and blood platelets and reduced blood flow to organs may lead to multiple organ failure. Seizures, heart failure, inflammation of the pancreas, and diabetes can also result. However, most children recover completely.

See a doctor right away if you or your child has any of the following symptoms with diarrhea:

  • High fever – temperature over 101.5°, measured orally
  • Blood in the stools
  • Diarrhea that lasts more than 3 days
  • Prolonged vomiting that prevents keeping liquid down and can lead to dehydration
  • Signs of severe dehydration, such as dry mouth, sticky saliva, decreased urination, dizziness, fatigue, sunken eyes, low blood pressure, or increased heart rate and breathing rate
  • Signs of shock, such as weak or rapid pulse or shallow breathing
  • Confusion or difficulty reasoning

How are foodborne illnesses diagnosed?

Your doctor may be able to diagnose foodborne illnesses from a list of what you’ve eaten recently and from results of appropriate laboratory tests. Diagnostic tests for foodborne illnesses should include examination of the feces. A sample of the suspected food, if available, can also be tested for bacterial toxins, viruses, and parasites.
 

How are foodborne illnesses treated?

Most cases of foodborne illnesses are mild and can be treated by increasing fluid intake, either orally or intravenously, to replace lost fluids and electrolytes. People who experience gastrointestinal or neurologic symptoms should seek medical attention.

In the most severe situations, such as HUS, hospitalization may be needed to receive supportive nutritional and medical therapy. Maintaining adequate fluid and electrolyte balance and controlling blood pressure are important. Doctors will try to minimize the impact of reduced kidney function. Dialysis may be needed until the kidneys can function normally. Blood transfusions also may be needed.
 

How are foodborne illnesses prevented?

Please check the Center for Disease Control website at: