Shigellosis (Bacillary Dysentery)

Key Features

Essentials of Diagnosis

• Cramps and bloody diarrhea

• High fever, malaise, convulsions

• Pus and blood in diarrheal stools examined microscopically

• Diagnosis confirmed by stool culture

General Considerations

• Shigellae are closely related to Escherichia coli

• Shigella is divided into four species: S dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei

• Shigellosis may be a serious disease, particularly in young children, and without supportive treatment an appreciable mortality rate results

• In older children and adults, disease tends to be self-limited and milder

• Usually transmitted by the fecal-oral route

Demographics

• Approximately 15,000–20,000 cases of shigellosis are reported each year in the United States

• S sonnei followed by S flexneri are the most common isolates

• S dysenteriae, which causes the most severe diarrhea of all species and the greatest number of extraintestinal complications, accounts for < 1% of all Shigella infections in the United States

Clinical Findings

Symptoms and Signs

• Incubation period is usually 1–3 days

• Onset is abrupt, with abdominal cramps, urgency, tenesmus, chills, fever, malaise, and diarrhea

• Hallucinations and seizures sometimes accompany high fever

• In severe forms, blood and mucus are seen in small stools (dysentery), and meningismus and convulsions may occur

• In older children, the disease may be mild and characterized by watery diarrhea without blood

• In young children, a fever of 39.4°C–40°C is common

• Symptoms generally last 3–7 days

Diagnosis

• The total WBC count varies, but often there is a marked shift to the left

• Stool may contain gross blood and mucus, and many neutrophils are seen

• Stool cultures are usually positive

Treatment

• In severe cases, immediate rehydration is critical

• A mild form of chronic malabsorption syndrome may supervene and require prolonged dietary control

• TMP-SMX (10 mg/kg/d trimethoprim and 50 mg/kg/d sulfamethoxazole, given in two divided doses orally for 5 days) and ampicillin (100 mg/kg/d divided in four doses)

  • Limited to cases in which results of susceptibility testing are known because of drug resistance

• Parenteral ceftriaxone is effective

• Azithromycin (12 mg/kg/d on day 1, then 6 mg/kg/d for 2 days) is effective

• Ciprofloxacin (500 mg, given twice daily for 5 days)

  • Not approved for use in children

  • However, it may be used in children who remain symptomatic and in need of therapy, and when multiply resistant strains limit other preferred choices

Outcome

Complications

• Dehydration, acidosis, shock, and renal failure

• In some cases, a chronic form of dysentery occurs, characterized by mucoid stools and poor nutrition

• Bacteremia and metastatic infections are rare but serious

• Febrile seizures are common

• Reactive arthritis (Reiter syndrome) may follow Shigella infection in patients with HLA-B 27 genotype

• Fulminating fatal dysentery and hemolytic-uremic syndrome occur ...