Background
Shigella organisms cause bacillary dysentery, a disease that has been described since early recorded history.
Pathophysiology
Shigella species (eg, Shigella dysenteriae, Shigella flexneri, Shigella sonnei, Shigella boydii) are aerobic, nonmotile, glucose-fermenting, gram-negative rods that are highly contagious, causing diarrhea after ingestion of as few as 180 organisms.[1]
Shigella species cause damage by 2 mechanisms, as follows: (1) invasion of the colonic epithelium, which is dependent on a plasmid-mediated virulence factor, and (2) production of enterotoxin, which is not essential for colitis but enhances virulence.
The organism is spread by fecal-oral contact; via infected food or water; during travel; or in long-term care facilities, day care centers, or nursing homes.[2]
Epidemiology
Frequency
United States
Approximately 450,000 cases of shigellosis are estimated to occur annually in the United States.
International
Shigellosis occurs worldwide, and it tends to occur whenever war, natural calamities (eg, earthquakes, floods), or unhygienic living conditions result in overcrowding and poor sanitation. S boydii and S dysenteriae occur more commonly internationally. Disease from Shigella species causes an estimated 1 million deaths and 165 million cases of diarrhea annually worldwide.
Mortality/Morbidity
Infection with Shigella species may be associated with extragastrointestinal complications.
- Bacteremia occurs primarily in malnourished children and carries a mortality rate of 20% as a result of renal failure, hemolysis, thrombocytopenia, gastrointestinal hemorrhage, and shock.[3]
- Hemolytic uremic syndrome may complicate infections with Shigella species and Escherichia coli, and it carries a mortality rate of greater than 50%.[1] Hemolytic uremic syndrome is characterized by acute hemolysis, renal failure, uremia, and disseminated intravascular coagulation.
- Metabolic disturbances: Hyponatremia secondary to syndrome of inappropriate antidiuretic hormone (ADH) secretion may occur.
- Leukemoid reaction: An elevated WBC count of 50,000/mm3 occurs in approximately 4% of patients, mainly in pediatric patients aged 2-10 years.
- Neurologic disease: Seizures, the most common neurologic complication, are always associated with fever and are generalized. They are typically nonrecurring and uncomplicated. Seizures are least common with S dysenteriae. The prevalence of seizures is approximately 10% across all ages.
- Encephalopathy with lethargy, confusion, and headache has been noted in up to 40% of children hospitalized with Shigella infections.
- Reactive arthritis (also known as Reiter syndrome) may occur.
Race
No racial differences exist.
Sex
No sexual predilection exists in Shigella infections.
Reactive arthritis, which is a triad of arthritis, urethritis, and conjunctivitis, occurs most commonly in men aged 20-40 years, and it occurs 2-4 weeks after infection with the Shigella species. Reactive arthritis is associated with the human leukocyte antigen (HLA)–B27 phenotype. The arthritis is asymmetrical and can be chronic and relapsing.
Age
Shigellosis is most common in children aged 6 months to 5 years.
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