Food poisoning

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 affected by a foodborne illness annually. Risk factors include the cross-contamination of food and improper handling and storage. 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.

• Pathogen: Staphylococcus aureus ^[1][2]
  • Gram-positive bacterium
  • Some strains produce heat-stable staphylococcal enterotoxins that cause food poisoning and, in severe cases, toxic shock syndrome.
  • While Staphylococcus aureus is destroyed by cooking, the heat-stable enterotoxins are not.
  • Bacteria proliferate in inadequately refrigerated food (canned meats, mayonnaise/potato salad, custards).
• Transmission: ingestion of preformed toxins in contaminated food
• Incubation period: 1– 8 hours
• Clinical features
  • Typically involves a short latency period; resolution of symptoms after 24–48 hours
  • Nausea, vomiting, abdominal discomfort, diarrhea
• Treatment
  • Supportive
  • Antibiotics are unnecessary.

• Pathogen: Bacillus cereus, a heat-stable, spore-forming ; gram-positive rod that produces two different enterotoxins
• Transmission
  • The bacteria grows in heated food that cools down too slowly or is improperly refrigerated.
  • Reheated rice; is a common source of infection: Spores survive the cooking process and germinate when rice is kept warm, which results in enterotoxin formation. ^[1]
• Incubation period and clinical findings
  • Enterotoxin I (a preformed cereulide) causes the emetic form: 30 minutes to 6 hours after ingestion, nausea and vomiting begin.
  • Enterotoxin II causes the diarrheal form: 6–15 hours after ingestion, watery diarrhea and abdominal pain begin, typically lasting for 24–48 hours.
• Treatment: supportive: , as antibiotics are not effective against toxins ^[3]

Poisoning from reheated rice can be serious (B. cereus).

Histamine fish poisoning

• Transmission: : Predominantly caused by ingestion of contaminated, inadequately refrigerated dark-meat fish, e.g. mackerel, bonito, mahi-mahi, and tuna
• Mechanism of action: : when temperature rises above a certain degree, histidine is transformed into histamine through histidine decarboxylases produced by bacteria
• Clinical features
  • Scombroid poisoning is often confused with fish allergy
  • After 5 minutes to 1 hour, symptoms similar to anaphylaxis appear:
    • Fever
    • Vomiting, diarrhea
    • Erythema, flushing, itching, urticaria
    • Oral burning sensation
  • Over time, symptoms may aggrevate to:
    • Respiratory distress due to bronchospasm
    • Hypotension
    • Angioedema
  • Symptoms usually resolve within 48 hours.
• Treatment
  • Antihistamines
  • Epinephrine and albuterol may be administered in severe cases.

Reef fish poisoning (ciguatoxin)

• Transmission: ingestion of reef fish containing Gambierdiscus toxicus
  • Barracuda
  • Moray eel
  • Snapper
  • Sea Bass
  • Amberjack
• Mechanism of action: opening of Na⁺ channels → depolarization
• Clinical features
  • Cardiovascular: hypotension, heart block, bradycardia
  • Gastrointestinal: diarrhea, nausea, vomiting
  • CNS: ataxia, vertigo
  • Numbness of mouth, lips, extremities
  • Reversal of hot and cold sensation
• Treatment: supportive

Puffer fish poisoning (tetrodotoxin)

• Transmission: : ingestion of puffer fish containing the potentially deadly neurotoxin
• Mechanism of action: blocks voltage-gated sodium channels, which inhibits action potential propagation
• Clinical features
  • Nausea, diarrhea
  • Muscle weakness, paralysis
  • Loss of reflexes
  • Paresthesias
• Treatment: supportive

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 article on bacterial gastroenteritis.

Predominantly vomiting

Pathophysiology: Vomiting is commonly due to delayed gastric emptying caused by changes to gastric motility.

Symptom onset and resolution are quick in S. aureus and B. cereus poisoning: S. aureus and B. cereus are fast and fureus.

Predominantly diarrhea

Watery diarrhea

• Pathophysiology: enterotoxin or bacterial invasion shifts water and electrolyte excretion/absorption in proximal small intestine → watery diarrhea
• Clinical features
  • Mild–moderate: abdominal pain, diarrhea
  • Severe
    • Tachycardia, hypotension
    • Fever
    • Bloody or profuse watery diarrhea
    • Metabolic acidosis
• Diagnostics: stool tests
  • WBC negative
  • No blood

Invasive diarrhea

• Pathophysiology: penetration of mucosa and subsequent invasion of reticuloendothelial system in the distal small intestine → enteric fever
• Diagnostics: stool tests
  • WBC positive (fecal mononuclear leukocytes)
  • Blood may be present.

Inflammatory diarrhea

• Pathophysiology: damage to the colonic mucosa → blood in stool, fever
• Diagnostics: stool tests
  • WBC positive (fecal polymorphonuclear leukocytes)
  • Blood present

Additional non-gastrointestinal symptoms

Common sources of fecal-oral transmission in intestinal diseases are the 5 F's: fingers, feces, food, fluids, flies.

• Food hygiene ^[17]
  • 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 ^[18]
  • 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.