Diarrhea, Infectious

Key Features

Essentials of Diagnosis

• Acute diarrhea: lasts < 2 weeks

• Chronic diarrhea: lasts > 2 weeks

• Mild diarrhea: 3 or fewer stools per day

• Moderate diarrhea: 4 or more stools per day with local symptoms (abdominal cramps, nausea, tenesmus)

• Severe diarrhea: 4 or more stools per day with systemic symptoms (fever, chills, dehydration)

General Considerations

• Acute diarrhea can be caused by a number of different factors, including

  • Emotional stress

  • Food intolerances

  • Inorganic agents (eg, sodium nitrite)

  • Organic substances (eg, mushrooms, shellfish)

  • Medications

  • Infectious agents (including viruses, bacteria, and protozoa)

• Inflammatory diarrhea

  • Suggests colonic involvement by invasive bacteria, by parasites or by toxin production

  • Common causes include

    • Shigella

    • Salmonella

    • Campylobacter

    • Yersinia

    • Invasive strains of Escherichia coli and other Shiga-toxin–producing strains of E coli (STEC)

    • Entamoeba histolytica

    • Clostridioides difficile

• Noninflammatory diarrhea

  • Common causes of this syndrome include

    • Viruses (eg, rotavirus, norovirus, astrovirus, enteric adenoviruses), vibriones (Vibrio cholerae, Vibrio parahaemolyticus)

    • Enterotoxin-producing E coli

    • Giardia lamblia

    • Cryptosporidia

    • Agents that can cause food-borne gastroenteritis

    • In developed countries, viruses (particularly norovirus) are an important cause of hospitalizations due to acute gastroenteritis among adults

• The term "food poisoning" denotes diseases caused by toxins present in consumed foods

• Epidemiologic features may be helpful in determining etiology:

  • Recent hospitalization or antibiotic use suggests C difficile

  • Recent foreign travel suggests Salmonella, Shigella, Campylobacter, E coli, or V cholerae

  • Undercooked hamburger suggests STEC

  • Outbreak in long-term care facility, school, or cruise ship suggests norovirus (including newly identified strains, eg, GII.4 Sydney)

  • Fried rice consumption is associated with Bacillus cereus toxin

Clinical Findings

• Inflammatory diarrhea

  • Frequent bloody, small-volume stools

  • Often associated with fever, abdominal cramps, tenesmus, and fecal urgency

• Noninflammatory diarrhea

  • Generally milder than inflammatory diarrhea

  • Large-volume watery diarrhea, often with nausea, vomiting, and cramps

• When incubation period of "food poisoning" is short (1–6 hours after consumption),

  • Vomiting is usually a major complaint

  • Fever is usually absent

  • The toxin is usually preformed and can be detected in the food; examples of pathogens with preformed toxins include Staphylococcus aureus or B cereus

• When the incubation period is longer—between 8 hours and 16 hours

  • Vomiting is less prominent

  • Abdominal cramping is frequent

  • Fever is often absent

  • The organism is present in the food and produces toxin after being ingested; the best example is Clostridium perfringens

Diagnosis

• Inflammatory diarrhea

  • Tests for fecal leukocytes or the neutrophil marker lactoferrin are frequently positive

  • Definitive etiologic diagnosis requires stool culture

• In cases of "food poisoning," toxin can be detected in food or stool specimens

• See Table 30–3