Clinical Features of Diseases Caused by Shigella

Bacillary dysentery is clinically similar regardless of infecting serotype; however, there are some clinical differences, particularly relating to the greater severity and risk for complications with S. dysenteriaeserotype 1 infection.

Incubation Period:
Ingestion of shigellae is followed by an incubation period of 12 hr to several days before symptoms ensue.

Clinical Manifestations:
Severe abdominal pain, high fever, emesis, anorexia, generalized toxicity, urgency, and painful defecation characteristically occur. Physical examination at this point may show abdominal distention and tenderness, hyperactive bowel sounds, and a tender rectum on digital examination.

The diarrhea may be watery and of large volume initially, evolving into frequent small-volume, bloody mucoid stools; most children (>50%) never progress to the stage of bloody diarrhea, whereas in others the 1st stools are bloody. Significant dehydration related to the fluid and electrolyte losses in both feces and emesis can occur. Untreated diarrhea may last 1–2 wk; only about 10% of patients have diarrhea persisting for more than 10 days.

Neurologic findings are among the most common extraintestinal manifestations of bacillary dysentery, occurring in as many as 40% of hospitalized infected children. Enteroinvasive E. coli can cause similar neurologic toxicity. Convulsions, headache, lethargy, confusion, nuchal rigidity, or hallucinations may be present before or after the onset of diarrhea. The cause of these neurologic findings is not understood.

Complications:
The most common complication of shigellosis is dehydration. Inappropriate secretion of antidiuretic hormone with profound hyponatremia may complicate dysentery, particularly when S. dysenteriaeis the etiologic agent. Hypoglycemia and protein-losing enteropathy may occur. Other major complications, particularly in very young, malnourished children, include sepsis and disseminated intravascular coagulation. Given that shigellae penetrate the intestinal mucosal barrier, these events are surprisingly uncommon.

Neonatal shigellosis is rare. Newborns may have only low-grade fever with mild non bloody diarrhea. However, complications occur more commonly than in older children and include septicemia, meningitis, dehydration, colonic perforation, and toxic megacolon