• Clinical science

Food poisoning

Abstract

Food poisoning, or foodborne illness, occurs following the ingestion of food or water contaminated with bacteria, bacterial toxins, viruses, parasites, or chemical substances. According to the Centers for Disease Control and Prevention (CDC), an estimated 1 in every 6 people in the US is annually affected with a foodborne illness. Risk factors include the cross-contamination of food, as well as improper handling and storage. In addition, immunocompromised individuals are at an increased risk of infection. Common pathogens attributed to food poisoning include Norovirus, Salmonella, Clostridium perfringens, Campylobacter jejuni, Staphylococcus aureus, and Escherichia coli. Incubation periods depend on the cause, and range from a few hours to days. The clinical presentation associated with food poisoning varies, but typical symptoms include diarrhea, nausea, vomiting, and abdominal cramping. Various laboratory tests (e.g., stool analysis, blood tests) help confirm the suspected diagnosis. Young children and the elderly are at greater risk for developing complications related to food poisoning and must be closely monitored. For most patients, supportive care, including fluid replenishment, is sufficient.

Staphylococcal food poisoning

  • Pathogen: Staphylococcus aureus
    • Gram-positive bacterium
    • Some pathogenic, virulent strains produce enterotoxins that cause the symptoms[1]
  • Transmission: ingestion of the toxins in contaminated food[1]
  • Characteristics
    • Typically involves a short latency period; resolution of symptoms after 24–48 hours
    • Bacteria proliferate in inadequately refrigerated food; (canned meats, mayonnaise/potato salad, custards).[2]
  • Incubation period:1–4 hours
  • Clinical findings: nausea, vomiting, abdominal discomfort, diarrhea
  • Treatment: supportive[2]

References:[3]

Bacillus cereus infection

  • Pathogen: Bacillus cereus, a heat-stable, spore-forming bacterium that produces two different enterotoxins
  • Transmission: : The bacterium grows in heated food that cools down too slowly or is improperly refrigerated. Reheated rice is a common source of infection.[1]
  • Incubation period and clinical findings
    • Enterotoxin I (emetic form): 30 min to 6 h after ingestionnausea and vomiting
    • Enterotoxin II (diarrheal form): 6–15 h after ingestion → watery diarrhea for 24–48 h
  • Treatment: Supportive[3]

"Food poisoning from reheated rice? Be serious!" (B. cereus).
References:[4][5]

Histamine fish poisoning (Scombroid)

  • Transmission: ingestion of contaminated, inadequately refrigerated fish (e.g., fish cakes)
  • Clinical findings
  • Treatment: Symptoms usually resolve within 48 h. Antihistamines may be administered in severe cases.

Overview of foodborne diseases

Foodborne diseases may be classified according to the predominating symptoms. An overview is provided in this section. For details regarding the bacterial pathogens see the learning card “Bacterial gastroenteritis”.

Predominently vomiting

Commonly due to delayed gastric emptying caused by changes to gastric motility.

Pathogen Foods/Transmission Incubation period Treatment

Staphylococcus aureus

(Enterotoxins cause the symptoms)

  • Canned meats, mayonnaise/potato salad, custards
  • 1–3 h
  • Supportive
Bacillus cereus
  • Reheated rice, food kept warm but not hot
  • Vomiting: 30 min to 6 h
  • Diarrhea: 6–15 h
  • Supportive

Noroviruses (e.g., Norwalk)

(Vomiting more common in children)

  • Fecal-oral
  • 12–48 h
  • Supportive

Predominently diarrhea

Watery diarrhea

Typical pathomechanism of watery diarrhea: pathogen or toxin enters gastrointestinal tract → binds epithelial cells, sometimes damaging microvilli → ↑ secretion or ↓ absorption of hydrophilic molecules or electrolytes (e.g., NaCl) → ↑ intestinal water due to osmosis → diarrhea.

Enterotoxin or bacterial invasion shifts water and electrolyte excretion/absorption in proximal small intestine → watery diarrhea

  • WBC negative
  • No blood
Pathogen Foods/Transmission Incubation period Treatment
Staphylococcus aureus
  • Inadequately refrigerated food
  • Reheated meat dishes
  • Undercooked meat and raw legumes
  • 6–24 h
  • Recent travel (e.g., Asia, Africa, the Middle East, Mexico, Central, and South America)
  • Undercooked meat, endogenous
  • Fecal-oral
  • 9 h to 3 days
Listeria monocytogenes
  • Cheese, deli meats, coleslaw, hot dogs, unpasteurized milk
  • 1–2 days
Vibrio cholerae

Enteric viruses (adenovirus, norovirus, rotavirus)

  • Fecal-oral
Cryptosporidium
  • Fecal-oral
  • 5–7 days
  • Immunocompetent patients: self-limiting; nitazoxanide may be shorten the duration
  • Immunocompromised patients: Antiretroviral therapy to elevate the CD4 cell count/restore the immune system is essential prior to eradication with antiparasitic drugs.
Cyclospora (Cryptosporidium cyclospora cayetanensis)
  • Fecal-oral
  • 5–7 days
Intestinal tapeworms
  • Larvae in undercooked pork/beef, raw freshwater fish
  • 6–8 weeks
  • Asymptomatic for years
  • Praziquantel, niclosamide

Invasive diarrhea

Pathogens penetrate the mucosa and invade the reticuloendothelial system of the distal small intestine → enteric fever

  • WBC positive (fecal mononoculear leukocytes)
  • Blood may be present
Pathogen Foods/Transmission Incubation period Treatment
Yersinia
Salmonella typhi or paratyphi
  • Poultry/eggs

Inflammatory diarrhea

Typical pathomechanism of inflammatory diarrhea: pathogen enters gastrointestinal tractinflammation → mucosal damage → barrier defect → diarrhea.

Bacteria or cytotoxins damage the colonic mucosa → blood in stool and fever

  • WBC positive (fecal polymorphonuclear leukocytes)
  • Blood present
Pathogen Association Foods/Transmission Incubation period Treatment
Salmonella (100s of strains, including S. enteritidis and S. typhimurium)
  • Poultry/eggs
  • Chicken products: eggs, raw chicken
  • 6–48 h
Campylobacter jejuni
  • Most common bacterial organism pathogen responsible for foodborne gastroenteritis in the US
  • Poultry
  • Fecal-oral
  • Days
Shigella dysenteriae
  • Second most common association with hemolytic-uremic syndrome (HUS)
Fecal-oral
  • Days
Yersinia enterocolitica
  • Contaminated milk, pork
  • Days
Vibrio (usually parahaemolyticus)
  • Shellfish
  • Undercooked seafood
  • 16–72 hours

Enterohemorrhagic Escherichia coli (EHEC)

  • O157:H7: most common pathogenic strain; associated with HUS
  • Undercooked meat; most common association with hemolytic-uremic syndrome (HUS)
  • Non-disinfected water; contaminated food, such as unpasteurized dairy products (milk, soft cheese) or apple cider
  • Fecal-oral
  • 3–4 days
(range: 24 h to 10 days)
  • Supportive
  • Antibiotics are contraindicated because they increase the risk of HUS
Clostridium difficile

Additional non-gastrointestinal symptoms

Pathogens Predominating symptoms Foods/Transmission Incubation period Treatment
Clostridium botulinum
  • Descending paralysis
  • Adults: respiratory support, antitoxin
  • Infants: respiratory support, hyperimmune human serum
  • Do not use antibiotics! .
Histamine fish poisoning
  • Inadequately refrigerated fish
  • 5 min to 1 h
Brucellosis (Brucella spp.)
  • Cyclical fever, arthralgias
  • Unpasteurized dairy products
  • Contact with animals (e.g., hunter)
  • 2-4 weeks (range: 5 days to 5 months)
Hepatitis A (Hepatitis A virus)
  • Jaundice, commonly following initial GI symptoms
  • Fecal-oral
  • 28 days (range 14–50 days)
  • Supportive (generally self-limiting)
  • Immune serum globulin
  • Vaccine

Vibrio vulnificus

  • Oysters, undercooked seafood
  • 1–7 days
Salmonella typhi and paratyphi
  • Fecal-oral
  • Hours
Ciguatera toxin
  • Paresthesia
  • Fish containing Gambierdiscus toxicus
  • 2–6 h
  • Supportive
  • Can last years

Common vectors for fecal-oral transmission in intestinal diseases are the 5 F's: fingers, feces, food, fluids, flies.
References:[5][6][7][1][8][9][10][11][12][13][14][15][16][17][17][18][19][20][2][21][22][23][24][25][26][27][28][3][29]

Food and water safety

  • Food hygiene
    • Wash hands and surfaces frequently
    • Wash fruits and vegetables with safe drinking water
    • Avoid cross-contamination by keeping raw meat products, eggs and seafood separated from other kinds of food
    • Use a food thermometer while cooking
    • Maintain a refrigerator temperature < 4°C (40°F)
    • When traveling (especially to developing countries): only consume fully cooked or dry (e.g., bread, crackers) foods, pasteurized dairy products, and fruits and vegetables you can peel or have properly washed yourself
  • Water hygiene
    • Do not consume untreated water or ice
    • Options if water treatment is unknown:
      • Consume sealed bottled beverages
      • Boil water for at least one minute before consuming
      • Use an appropriate filter

There is a simple rule to avoid foodborne illness while traveling: Boil it, cook it, peel it, or forget it!
References:[30][31]