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Division of Consolidated Laboratory Services

SHIGA TOXIN TESTING

Laboratory: Microbial Reference and Molecular Detection and Characterization

Test Description: Isolation and confirmation of Shiga Toxin producing organisms.

Order Approval Required? No

Specimen Type: Isolate Slant; GN Broth, MacConkey Broth; For follow up samples submitted through Virginia Department of Health (VDH) submit Cary Blair preserved stool.

Collection Container: Cary-Blair Transport Media

Optimal Volume: Cary Blair containers should have enough feces to bring the level of medium up to the fill line on the container

Collection Guidelines: Stool specimens should be collected as soon as possible after diarrhea begins, while patient is actively ill and before antibiotic treatment has been administered; Refer to the Centers for Disease Control and Prevention (CDC) Website http://www.cdc.gov/foodsafety/outbreaks/investigating-outbreaks/specimen-collection.html

Storage Container: Not Applicable

Storage Instructions: Store GN or MacConkey Broth at 2-8°C; Cary-Blair stool store at room temperature

Transportation Instructions: Broths transport at 2-8°C; Do not transport on dry ice. Provide insulation between specimen and ice packs. Cary-Blair stools transport at room temperature

Test Methodology: Conventional culture methods and molecular methods.

Additional Information: Laboratories that use a Shiga toxin Enzyme Immunoassay (EIA) methodology but do not perform simultaneous culture for Shiga toxin producing Escherichia coli should forward all positive stool specimens or positive enrichment broths to Division of Consolidated Laboratory Services (DCLS) for confirmation and further characterization.

Causes For Rejection:

  • Samples with no name or identifier, mismatched samples and test request forms.
  • Media that has expired prior to inoculation.
  • Incorrect or broken transport media.
  • Evidence of exposure to temperature extremes during transport.

Possible Results:

  • Polymerase Chain Reaction (PCR) Shiga-Toxin screen negative
  • Unable to Isolate Shiga-Toxin Producing Organism on Culture
  • Full isolate identification. Isolate may be forwarded to the Centers for Disease Control and Prevention (CDC) for further testing if necessary.