Food Poisoning – Causes, Symptoms, Diagnosis, Treatment

Causes of Food Poisoning

Bacteria that can cause diarrhea in human live in the intestines of healthy or infected people, or animals, like cattle, poultry or pets. Their stool may contaminate drinking or recreational water, soil, vegetables on fields, milk during milking, meat during slaughter, or food prepared with the hands contaminated with stool. Beside that, bacteria arising from the air or food storing surfaces may quickly multiply in a non-cooled food.

Sources of Infection:

  • Food borne infection (food poisoning): undercooked ground beef (hamburgers), chicken or other meat, shellfish (oyster, scallops), raw eggs (mayonnaise), raw unwashed fruits and vegetables, unpasteurized milk or fruit juices, or non-adequately stored or cooled food
  • Water borne infection: contaminated drinking or recreational water
  • Stool-to-mouth (fecal-oral) infection via stool-contaminated hands, toys, utensils, soil, etc.
  • Infections of ear, nose and throat, and urinary infections may also cause acute bacterial diarrhea.

Bacteria, Commonly Involved in Food Poisoning

  • E.coli 0157:H (2)
  • Campylobacter (3)
  • Salmonella (4)
  • Staphylococcus aureus (staph food poisoning)
  • Clostridium perfringens
  • Shigella (5,6)
  • Listeria – in pregnant women and persons with lowered immunity (7)
  • Yersinia
  • Vibrio cholerae (causing cholera)

Intestinal Changes in Bacterial Food Poisoning

Bacteria may cause inflammation of the stomach and small intestine (gastroenteritis), colon (colitis) or rectum (proctitis). Inflammation may lead to reduced absorption of nutrients and water from the intestine resulting in diarrhea. In heavy infection ulcers may develop, and in most severe cases bacteria may enter the blood (sepsis) and affect other organs.

Symptoms of Bacterial Food Poisoning

Symptoms of food poisoning caused by bacteria include:

  • Explosive diarrhea with frequent, loose or watery stools, urgency, bloating, abdominal cramps. If enough bacteria are ingested, diarrhea appears suddenly, usually within 48 hours (or within 5 days), and lasts for 1-3 days (or up to 10 days or more in heavy infection).
  • Nausea, vomiting (occasionally)
  • General malaise with fever (occasionally)
  • In severe diarrhea, symptoms of dehydration, like thirst, tiredness, sunken eyes, low amount of morning urine, may quickly appear

If you have persistent diarrhea or soft stools after a travel, read about traveler’s diarrhea and intestinal parasites, like Giardia and intestinal worms contracted by food.

The stool of the infected person is contagious during diarrhea and up to two weeks after the healing (in shigellosis possibly up to 1 year or more after symptoms cessation).

Diagnosis of Bacterial Food Poisoning

Doctor can suspect you have bacterial food poisoning from the history of

  • Sudden onset diarrhea
  • Diarrhea appearing several hours after eating fastfood, having a meal in a suspicious restaurant or drinking water from rivers or lakes
  • Other people who have eaten the same food as you and had diarrhea within the next two days
  • Close contact with people having diarrhea
  • Arriving from a country with good hygiene into country with poor hygiene habits.

If you have heavy diarrhea, doctor might order a stool culture test to determine causing bacteria to be able to prescribe you an appropriate antibiotic. Hemoccult, test for occult blood in the stool, is done when intestinal bleeding is suspected.

Treatment of Diarrhea Due to Bacterial Food Poisoning

Mild acute bacterial diarrhea usually heals on its own within three days. Everyone with acute diarrhea should drink enough fluid from the onset of symptoms to prevent dehydration. Antibiotics are prescribed only in prolonged (>5 days), profuse (>6 stools/day) or bloody diarrhea, in fever (> 38.5 °C or 101.3 °F), or severe abdominal pain.

Antibiotics may shorten the course of heavy bacterial diarrhea, but NOT if the cause is E.coli 0157:H, Staphylococcus aureus, or Clostridium perfringens, where gastro-intestinal inflammation is the result of bacterial toxins and not bacteria themselves.

Remedies in Food Poisoning

Anti-diarrheal remedies, like loperamide, diphenoxylate, bismuth sub-salycilate, probiotics, or prebiotics are of small value (1).

Related Articles:


  1. Treatment of acute diarrhea  (
  2. E.coli 0157:H  (
  3. Campylobacter  (
  4. Salmonella  (
  5. Shigella carriers  (
  6. Shigella  (
  7. Listeria  (
About Jan Modric (249 Articles)
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