Shigella

Shigella

Compiled By: Julie A. Albrecht, Ph.D., Associate Professor

The Organism: Shigella are facultative anaerobic bacteria that produces an endotoxin referred to as a shiga toxin. The organism is fragile, easily killed by heat during cooking or processing.

PDF Fact Sheet

Sources of the organism:

  • Fecally contaminated water
  • Food handler with poor personal hygiene practices

Associated foods:

  • Any food contaminated by a food handler with poor hygiene practices
  • Contaminated water
  • Salads (potato, tuna, shrimp, macaroni, chicken)
  • Raw vegetables
  • Sandwiches

Microorganism Characteristics: Gram-negative nonsporeforming facultative anaerobic rod-shaped bacteria which produces an endotoxin

Growth conditions:

  • Temperature range: 10-40°C (50-104°F).
  • Optimum Temperature: 37°C (98.6°F)
  • pH range: Organisms do not survive below pH 4.5
  • Salt tolerance: 5-6%

The Disease: Shigellosis, also known as bacillary dysentery, is caused by several bacteria of the genus Shigella. Numerous species of Shigella are associated with food borne illness outbreaks. Shigella sonnei is the major cause of shigellosis from food. Virulent Shigella organisms attach to and penetrate the epithelial cells of the intestine. After invasion, they multiply and spread to the epithelial cells.

Symptoms include:

  • Abdominal cramps
  • Diarrhea
  • Vomiting
  • Fever
  • Stools may contain mucus or blood

Onset time:

  • 12-48 hours

Infective Dose:

  • Small numbers (10-100 cells) of viable Shigella cells consumed by a susceptible host.

Duration of symptoms:

  • 4-7 days

Control:

  • Proper hand washing after using the bathroom.
  • Use properly treated water.
  • Cook foods to appropriate temperatures.
  • Chill food to 41°F within 4 hours.