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Chapter 40. The Intestines: II. Infections; Inflammatory Bowel Diseases

Classification

Intestinal infections can be divided into 3 broad groups (Table 40-1):

Table 40–1. Infections of Intestines.
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Table 40–1. Infections of Intestines.
Organism Source of Toxin or Infectious Agent Clinical Illness
Toxin–mediated
Vibrio cholerae Contaminated water Severe diarrhea
Escherichia coli, toxigenic Food, water Traveler's diarrhea
Staphylococcus aureus toxin Toxin in food Food poisoning
Clostridium perfringens Reheated foods Food poisoning
Bacillus cereus Reheated foods Food poisoning
Vibrio parahaemolyticus Shellfish Diarrhea and dysentery
Clostridium botulinum Neurotoxin in food Botulism
Clostridium difficile Enterotoxin Pseudomembranous enterocolitis
Invasive infections
Viral
Rotaviruses and adenoviruses Person to person Infantile diarrhea
Parvoviruses Person to person “Stomach flu”
Cytomegalovirus Person to person Enterocolitis (mainly in immunocompromised patients)
Bacterial
Salmonella species Food, milk, or water Food poisoning
Salmonella typhi Food, water Typhoid
Shigella species Food, water Dysentery
Enteropathogenic E coli Mostly person to person Diarrhea and dysentery
Campylobacter fetus Animals, infected persons, food Childhood diarrhea
Yersinia species Infected person, food Mesenteric adenitis, diarrhea
Mycobacterium tuberculosis Infected person or milk Chronic disease
Atypical mycobacteria Infected person, soil Chronic diarrhea (mainly in immunodeficient patients)
Protozoal
Entamoeba histolytica Fecal contamination (cysts) Amebic colitis
Metazoan parasites (Table 40–4)
Noninvasive infections
Giardia lamblia Contaminated water Giardiasis
Cryptosporidium, Isospora Contaminated food, water Diarrhea (mainly in immunocompromised patients)
Metazoan parasites (see Table 40–4)

  1. Enterotoxin-mediated, where the disease is caused by a bacterial exotoxin; the organism does not invade the tissues and in some cases does not even enter the body (staphylococcal toxin, botulism), as the exotoxin is preformed in food.

  2. Invasive infections, where the organism invades the intestinal mucosa.

  3. Noninvasive infections, where the organism exists in the intestinal lumen and does not invade the tissues.

Most intestinal infections are transmitted by fecal contamination of food or drinking water. They are common in parts of the world where public health sanitary measures such as disposal of feces and purification of water supplies are not adequate.

Clinically, infections that involve the small intestine result in profuse watery diarrhea, while those that involve the colon produce dysentery (frequent small-volume diarrhea with blood and mucus). Fever is present in most invasive infections but is often absent in enterotoxin-mediated diseases.

Diagnosis

(Table 40-2)

Table 40–2. Laboratory Diagnosis of Intestinal Infections.
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Table 40–2. Laboratory Diagnosis of Intestinal Infections.
Visual examination of feces Large volume, watery (“rice and water”) stool indicates severe secretory diarrhea. Seen in toxin–mediated small intestinal infections (eg, cholera).
Moderate volume, liquid brown or green (“pea soup”) stool. Seen in many small bowel infections (eg, gastroenteritis, typhoid fever).
Small volume stool composed largely of blood and mucus (“red currant jelly stool”). Seen in colonic diseases with mucosal ulceration.
Microscopic examination for neutrophils Neutrophils absent: toxigenic bacteria, viruses, protozoa.
Neutrophils ...

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