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Key Features

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Essentials of Diagnosis
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  • Cramps and bloody diarrhea

  • High fever, malaise, convulsions

  • Pus and blood in diarrheal stools examined microscopically

  • Diagnosis confirmed by stool culture

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General Considerations
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  • 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

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Demographics
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  • 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

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Clinical Findings

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Symptoms and Signs
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  • 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

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Diagnosis

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  • 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

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Treatment

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  • 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

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Outcome

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Complications
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  • 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 rarely

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Prognosis
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  • Excellent if vascular collapse is ...

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