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Diarrhea: Is It Food Poisoning or Infection?

  • Medical Author:
    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Diarrhea Is It Food Poisoning or Infection Related Articles

What Is Food Poisoning?

Food poisoning is a general term that refers to gastrointestinal illnesses (usually diarrhea and/or vomiting) caused by food that is contaminated with bacteria, parasites, viruses, or toxic substances. The actual cause of most individual episodes of food poisoning is usually not pursued (for example, a culture is not done), because most episodes are mild or moderate in severity and are over in a few hours to a few days. In fact, the diagnosis of food poisoning usually is made only presumptively, based on the patient's symptoms and the circumstances. Even in outbreaks of suspected food poisoning that involve many people, when careful studies are done, a specific cause is found no more than half of the time.

What causes food poisoning?

Bacteria are the cause of most outbreaks of food poisoning for which a specific cause is determined. Bacteria cause food poisoning in three ways. After reaching the intestines, they may multiply and release toxic substances into the intestine that cause diarrhea and/or vomiting without damaging the intestine itself. The bacteria also may multiply within the intestines and produce toxic substances that damage the lining of the intestine or they may invade and damage the intestine directly. Finally, some bacteria produce toxic substances before the food is eaten that cause diarrhea and/or vomiting. These bacteria do not need to multiply within the intestines, and the toxic substances they produce do not damage the intestine.

How is food poisoning diagnosed?

To know with certainty that a bacterium is causing food poisoning, the bacterium must be cultured, usually from stool and rarely from vomitus. If the food suspected of causing the poisoning still is available, the food can be cultured. Identification of the causative bacterium may require a determination of the bacterial subtype since not all bacteria of one type, for example, E. coli, cause illness. In some cases, the bacteria isolated from the culture may be tested to see if they produce toxic substances. In food poisoning caused by toxic substances formed by bacteria in food before the food is ingested, for example, staphylococcal food poisoning, the toxic substance can be sought in the food, stool, or vomitus. The identification of toxic substances, however, is complex and is not done by most bacteriology laboratories.

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References
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care

REFERENCE:

CDC.gov. Travelers' Diarrhea.
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