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Food Poisoning, Bacterial
Jewell P. Carr, MD
Daniel J. Fisher, MD
image BASICS
  • Food poisoning (also known as foodborne illness) is a state resulting from the consumption of contaminated food (1).
  • The illness may be caused by bacterial, parasitic, or viral infection or by toxins produced by bacteria (2).
  • The Centers for Disease Control and Prevention (CDC) estimates that roughly 1 in 6 Americans (48 million people) get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases annually (3).
  • Contaminated produce is the most common source of diarrhea due to foodborne infection (1).
  • No pathogen is identified in 80% of cases of foodborne illness (3).
  • Noroviruses are responsible for >50% of cases of foodborne illness (1).
  • According to CDC data, the bacterial pathogens most commonly contributing to foodborne illness are Salmonella (nontyphoidal) Campylobacter, Clostridium perfringens, and Staphylococcus aureus (3).
  • Short incubation period (1 to 6 hours): likely preformed toxin-induced
    • Bacillus cereus
      • Food sources: improperly cooked rice/fried rice and red meats
      • Causes sudden onset of severe nausea and vomiting. Diarrhea may be present.
    • S. aureus
      • Food sources: nonrefrigerated or improperly refrigerated meats and potato and egg salads
      • Causes sudden onset of severe nausea and vomiting. Abdominal cramps and fever may be present.
  • Medium incubation period (8 to 16 hours)
    • Bacillus cereus (toxin)
      • Food sources: meat, stew gravy, vanilla sauce
      • Causes watery diarrhea, abdominal cramps, nausea
    • C. perfringens
      • Food sources: dry/precooked meats and poultry
      • Causes watery diarrhea, nausea, abdominal cramps
  • Long incubation period (>16 hours)
    • Toxin-producing organisms:
      • Clostridium botulinum: Source is commercially canned or improperly home-canned foods. Causes vomiting, diarrhea, slurred speech, diplopia, dysphagia, and descending muscle weakness/flaccid paralysis
      • Enterohemorrhagic Escherichia coli (e.g., 0157:H7): Food sources are undercooked beef, especially hamburger, unpasteurized milk, raw fruits and vegetables, and contaminated water. Causes severe diarrhea that often becomes bloody, abdominal pain, vomiting. More common in children <4 years of age
      • Enterotoxigenic E. coli: Food sources are foods or water contaminated by human feces. Causes watery diarrhea, abdominal cramps, and vomiting
      • Vibrio cholerae: Food sources are contaminated water, fish, and shellfish, especially food sold by street vendors. Causes profuse watery diarrhea and vomiting, which can lead to severe dehydration and death within hours
    • Invasive organisms: often bloody stool and fever
      • Salmonella: Food sources are contaminated eggs, poultry, unpasteurized milk or juice, cheese, contaminated raw fruits and vegetables, and contaminated peanut butter. Causes watery diarrhea, fever, abdominal cramps, vomiting
      • Campylobacter jejuni: Food sources are raw and undercooked poultry, unpasteurized milk, and contaminated meats. Causes diarrhea (may be bloody), cramps, vomiting, fever
      • Shigella: Food sources are food or water contaminated by human fecal material. Causes abdominal cramps, fever, diarrhea
      • Vibrio parahaemolyticus: Food source is raw shellfish. Causes nausea, vomiting, diarrhea, abdominal pain
      • Vibrio vulnificus: Food source is undercooked and raw seafood; wounds exposed to sea water. Causes vomiting, diarrhea, abdominal pain, bacteremia, wound infections; can be fatal in patients with liver disease or those who are immunocompromised
      • Yersinia enterocolitica and Y. pseudotuberculosis: Food sources are undercooked pork, unpasteurized milk, tofu, contaminated water. Causes appendicitis-like symptoms: abdominal pain, fever, diarrhea, vomiting; occurs primarily in older children and younger adults
      • Listeria: Sources include unpasteurized/contaminated milk, soft cheese, and processed/delicatessen meats. Causes nausea, vomiting, fever, watery diarrhea
  • Recent travel to a developing country (1)
  • Food handlers, daycare attendees, nursing home residents, and recently hospitalized patients (2)
  • Altered immunity due to underlying disease or medications (1); patients taking antacids, H2 blockers, and proton pump inhibitors (1)
  • Cross-contamination and subsequent ingestion of improperly prepared and stored foods
  • When preparing food at home:
    • Wash hands, cutting boards, and surfaces before food preparation and after preparing each food item.
    • Wash fresh produce thoroughly before eating.
    • Keep raw meat, poultry, fish, and their juices away from other food that will not be cooked (e.g., salad).
    • Do not put cooked protein or washed produce back into containers or on surfaces where unwashed or raw food was stored.
    • Thoroughly cook meat to the following internal temperature:
      • Fresh beef, veal, pork, and lamb: 145°F
      • Ground meats and egg dishes: 160°F
      • Poultry: 165°F
      • Cook chicken eggs thoroughly until the yolk is firm.
    • Refrigerate leftovers within 2 to 3 hours in clean, shallow, and covered containers. If the temperature is >90°F, refrigerate within 1 hour.
  • When traveling to underdeveloped countries:
    • Eat only freshly prepared foods.
    • Avoid beverages and foods prepared with nonpotable water.
    • Other risky foods include raw or undercooked meat and seafood, unpeeled raw fruits, and vegetables.
    • Bottled, carbonated, and boiled beverages are generally safe to drink.
  • Concerning prevention, improved hygiene and sanitation reduces the risk of traveler's diarrhea, but the prevention strategy “Boil it, Cook it, Peel it, or Forget it” has inconsistent and limited evidence (4,5)[C].
  • Chemoprophylaxis for traveler's diarrhea (trips <14 days):
    • Bismuth subsalicylate 525 mg QID (4)[A]
    • Ciprofloxacin 500 mg daily or BID (4)[A]
    • Rifaximin 200 mg daily or BID (4)[A]
  • Focus on signs of dehydration: delayed capillary refills, increased skin turgor, dry mucous membranes, and orthostatic changes (2).
  • Fever may be suggestive of a more invasive or toxin producing bacteria (2).
  • Abdominal exam: important to assess for pain and to differentiate between other acute abdominal processes (2)
  • Rectal exam may be useful to assess for blood, rectal pain or consistency of stool (2).
  • Infectious gastrointestinal illness of any kind (i.e., viral or parasitic)
  • C. difficile colitis
  • Inflammatory bowel disease
  • Appendicitis and other acute abdominal surgical processes
  • Hepatitis
  • Malabsorption
Initial Tests (lab, imaging)
  • Culture of stool and sensitivity, fecal leukocytes, and Hemoccult testing; consider ova and parasites if dehydration, history of foreign travel, or symptoms lasting >2 weeks (1)[C].
  • CBC, BMP for severe cases with dehydration, inpatient, and nursing home exposure (1)[C]
  • P.387

  • Flexible sigmoidoscopy and colonoscopy are reserved for severe cases or when pathogen is suspected in setting of negative stool cultures (1).
  • Abdominal CT may be helpful when intra-abdominal pathology or bowel disease are in the differential (1).
Follow-Up Tests & Special Considerations
Epidemiologic investigation may be warranted.
Most cases of food poisoning are self-limiting and do not require medication.
First Line
  • Children, the elderly, and pregnant patients with signs of mild diarrhea should be started on oral rehydration solution to prevent dehydration (2)[C].
  • Oral rehydration options can be purchased or mixed simply from common home ingredients: 6 tsp sugar and 1/2 tsp salt in 1 L of clean, potable water (2)[B].
  • Travelers may consider empiric treatment for diarrhea with a single dose of ciprofloxacin 750 mg together with loperamide (2)[A].
  • Empiric antibiotic therapy for traveler's diarrhea should be considered in cases of moderate to severe disease (4)[A].
Second Line
For severe cases of food poisoning (up to 8% have bacteremia) or if the patient has a prosthetic valve, the following medications are recommended.
  • B. cereus (2)
    • Supportive care only
  • Campylobacter jejuni (1,2,5)
    • Mild: supportive care only-antibiotics may induce resistance (5)
    • Severe: azithromycin 500 mg/day for 3 to 5 days or ciprofloxacin 500mg BID to QID for 5 to 7 days
  • C. botulinum
    • Supportive care. Antitoxin can be helpful if administered early in the course of the illness.
  • C. perfringens
    • Supportive care only
  • C. difficile (1,2,6)
    • Mild disease: metronidazole 500 mg TID for 10 days (6)[A]
    • Moderate disease: vancomycin 125 mg PO QID for 14 days (6)[A]
    • Severe disease: vancomycin 500 mg PO QID plus metronidazole 500 mg IV every 8 hours (6)[A]; or fidaxomicin 200 mg BID for 10 days
    • Discontinue offending antibiotic if applicable.
  • Enterohemorrhagic E. coli (e.g., 0157:H7) (1)
    • Supportive care only. Closely monitor renal function, hemoglobin, and platelets. Infection associated with hemolytic uremic syndrome (HUS). Antibiotics may increase this risk.
  • Enterotoxigenic E. coli (common cause of traveler's diarrhea) (1,2,4,5)
    • Generally self-limited. Antibiotics shorten course of illness (4,5)[A]
    • Ciprofloxacin 500 mg BID or 750 mg daily for 1 to 3 days; azithromycin 1 g × single dose or daily for 3 days; or rifaximin 200 mg TID for 3 days
  • Salmonella, nontyphoidal (1,2,4,5)
    • No therapy in mild disease-increases duration of shedding without reducing disease duration (5)
    • Moderate: ciprofloxacin 500 mg BID for 5 to 7 days, levofloxacin 500 mg daily for 7 to 10 days or TMP/SMX DS 160/800 mg twice per day for 5 to 7 days
    • Severe diarrhea, immunocompromised, systemic signs, positive blood cultures: IV ceftriaxone 1 to 2 g daily for 7 to 10 days
  • Shigella (1,2)
    • Ciprofloxacin 500 mg BID or 750 mg daily for 3 days, or 2-g single dose; alternative options: azithromycin 500 mg twice per day for 3 days, TMP/SMX DS 160/800 mg twice per day for 5 days, or ceftriaxone 2 to 4 g single dose
  • S. aureus (1)
    • Supportive care only
  • Noncholeraic Vibrio (1)
    • Ciprofloxacin 750 mg daily for 3 days or azithromycin 500 mg daily for 3 days
  • Vibrio cholerae (1)
    • Doxycycline 300 mg 1-time dose in most cases or tetracycline 500 mg QID for 3 days or erythromycin 250 mg TID for 3 days or azithromycin 500 mg/day for 3 days
  • Yersinia (2)
    • Usually supportive care only
    • Severe: doxycycline combine with aminoglycoside; TMP/SMX DS 160/800 mg BID for 5 days; or ciprofloxacin 500 mg BID for 7 to 10 days
  • For severe nausea and vomiting, promethazine is effective in adults. Ondansetron is effective in children (4).
  • Loperamide 4 mg initially, then 2 mg after each loose stool to a maximum of 8 mg in a 24-hour period may be used unless high fever, bloody diarrhea, and/or severe abdominal pain present (signs of enteroinvasion) (4)[A]
  • Bismuth subsalicylate (Pepto-Bismol) 525 mg QID is moderately effective in traveler's diarrhea (4)[A].
  • Probiotics (i.e., Lactobacillus sp.) have been shown to reduce severity and sometimes duration by 24 hours. May also decrease likelihood of antibiotic-associated diarrhea (1,2). However, the evidence for their use is inconsistent (4)[C].
  • Diligent hand washing during course will decrease spread (2)[A].
  • Avoid food while nausea is present, but drink plenty of fluids in frequent sips.
  • As the nausea subsides, drink adequate fluids; add in bland, low-fat meals; and rest. Avoid alcohol, coffee, nicotine, and spicy foods.
  • Nursing infants should continue to be breastfed on demand, and infants and older children should be offered their usual food.
  • For diarrhea, consider a bland diet (BRAT: Bananas, Rice, Apples, Toast-dry).
  • Limiting dairy till 24 hours after last diarrhea episode may assist in symptom reduction.
Most infections are self-limited and will resolve over the course of 4 to 5 days. If antibiotics are given in moderate to severe traveler's diarrhea, the duration may shorten to a day and a half (Steffen).
1. DuPont HL. Acute infectious diarrhea in immunocompetent adults. N Engl J Med. 2014;370(16):1532-1540.
2. Barr W, Smith A. Acute diarrhea in Adults. Am Fam Physician. 2014;89(3):180-189.
3. Centers for Disease Control and Prevention. Trends in Foodborne Illness in the United States, 2013. Atlanta, GA: Centers for Disease Control and Prevention; 2014. http://www.cdc.gov/foodborneburden/trends-in-foodborne-illness.html.
4. Steffen R, Hill DR, Dupont HL. Traveler's diarrhea: a clinical review. JAMA. 2015;313(1):71-80.
5. Zollner-Schwetz I, Krause R. Therapy of acute gastroenteritis: role of antibiotics. Clin Microbiol Infect. 2015;21(8):744-749. http://dx.doi.org/10.1016/j.cmi.2015.03.002.
6. Leffler DA, Lamont JT. Clostridium difficile infection. N Engl J Med. 2015;372(16):1539-1548.
Additional Reading
  • Allen SJ, Martinez EG, Gregorio GV, et al. Probiotics for treating acute infectious diarrhoea. Cochrane Database Syst Rev. 2010;(11):CD003048.
  • Kalyoussef S, Feja KN. Foodborne illnesses. Adv Pediatr. 2014;61(1):287-312.
See Also
Appendicitis, Acute; Botulism; Brucellosis; Dehydration; Diarrhea, Acute; Guillain-Barré Syndrome; Hypokalemia; Intestinal Parasites; Salmonella Infection; Typhoid Fever
  • A05.9 Bacterial foodborne intoxication, unspecified
  • A02.0 Salmonella enteritis
  • A04.5 Campylobacter enteritis
Clinical Pearls
  • Consider bacterial food poisoning when multiple people present after ingesting the same food with fevers and blood/mucus in stool or have recently returned from a developing nation.
  • Consider culture and antibiotics in a prolonged febrile state with blood/mucus in stool, septicemic states, and traveler's diarrhea.
  • With signs of enteroinvasion (high prolonged fever, bloody diarrhea, severe pain, septicemia), consider withholding antispasmodics (e.g., loperamide).