Shigella dysenteriae may cause disease by producing Shiga toxin, either alone or combined with tissue invasion. The incubation period is 1 to 7 days. Infected adults may shed organisms for 1 month. Infection is spread by person-to-person contact or by the ingestion of contaminated food with 10 to 100 organisms. The colon is selectively affected. High fever and febrile seizures may occur in addition to diarrhea.
Only certain strains of E. coli produce diarrhea. E. coli strains associated with enteritis are classified by the mechanism of diarrhea: enterotoxigenic (ETEC), enterohemorrhagic (EHEC), enteroinvasive (EIEC), enteropathogenic (EPEC), or enteroaggregative (EAEC). ETEC strains produce heat-labile (cholera-like) enterotoxin, heat-stable enterotoxin, or both. ETEC causes 40% to 60% of cases of traveler’s diarrhea. ETEC adhere to the epithelial cells in the upper small intestine and produce disease by liberating toxins that induce intestinal secretion and limit absorption. EHEC, especially the E. coli O157:H7 strain, produce a Shiga-like toxin that is responsible for a hemorrhagic colitis and most cases of diarrhea associated with hemolytic uremic syndrome (HUS), which is a syndrome of microangiopathic hemolytic anemia, thrombocytopenia, and renal failure (see Chapter 164). EHEC is associated with contaminated food, including unpasteurized fruit juices and, especially, undercooked beef. EHEC is associated with a self-limited form of gastroenteritis, usually with bloody diarrhea, but production of this toxin blocks host cell protein synthesis and affects vascular endothelial cells and glomeruli, resulting in the clinical manifestations of HUS. EIEC invades the colonic mucosa, producing widespread mucosal damage with acute inflammation, similar to Shigella. EPEC is responsible for many of the epidemics of diarrhea in newborn nurseries and in day care centers.
Campylobacter jejuni is spread by person-to-person contact and by contaminated water and food, especially poultry, raw milk, and cheese. The organism invades the mucosa of the jejunum, ileum, and colon. Yersinia enterocolitica is transmitted by pets and contaminated food, especially chitterlings. Infants and young children characteristically have a diarrheal disease, whereas older children usually have acute lesions of the terminal ileum or acute mesenteric lymphadenitis mimicking appendicitis or Crohnʼs disease. Postinfectious arthritis, rash, and spondylopathy may develop.
Clostridium difficile causes C. difficile-associated diarrhea or antibiotic-associated diarrhea, secondary to its toxin. The organism produces spores that spread from person to person.
C. difficile-associated diarrhea may follow exposure to any antibiotic.