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The Delaware Public Health Laboratory (DPHL) provides testing to assist in identification of foodborne illness outbreaks.

DPHL supports other state partners when investigating tainted foods or suspected food-borne outbreaks. Infectious disease epidemiologists and the Office of Food Protection Health Systems Protection (HSP) can refer cases to DPHL for testing. Using symptoms and adverse reactions attributed to consuming suspected food, Epi and HSP guide DPHL in determining the appropriate method for detecting the food borne pathogen. Target organism(s) must be specified on the Request for Non-Clinical Preparedness Testing form and the Chain of Custody form must be completed at the time of delivery to the lab.

Standard procedures for processing food are more complicated than handling routine specimens. Foods cannot be screened for numerous pathogens due to the nature of the testing. Target organisms must be identified so that the food can be enriched specifically for that organism. Special media is required for fastidious organisms, usually found in mixed flora. Communication with the laboratory prior to delivery of the specimen(s) is a requirement.

Currently there are no successfully validated methods for detection of Norovirus in foods. If Norovirus infection is suspected, stool samples can be tested from suspected food handlers, or those persons suspected of being infected. Stools should be collected in sterile leak proof containers with 2 unique identifiers and submitted to the laboratory as soon as possible with completed Test Requisition Form. Requests for Norovirus testing must be approved and coordinated through the Office of Infectious Disease Epidemiology (OIDE).


Pathogen isolation and identification:

  • Bacillus anthracis
  • Bacillus cereus
  • Brucella spp.
  • Burkholderia spp.
  • Shiga-toxin producing E. coli
  • Francisella tularensis
  • Listeria spp.
  • Salmonella spp.
  • Shigella spp.
  • Campylobacter spp.
  • Staphylococcus aureus
  • Yersinia pestis
  • Vibrio spp. (For testing Vibrio in shellfish, please contact DNREC.)

Molecular Testing (real-time PCR):

  • Bacillus anthracis
  • Francisella tularensis
  • Yersinia pestis
  • Shiga toxin-producing E. coli (STEC): stx1, stx2, and wzy (0157:H7)

Whole Genome Sequencing (WGS):

  • Salmonella species
  • Shigella species
  • Shiga toxin-producing E. coli (STEC)
  • Vibrio species
  • Campylobacter spp.
  • Listeria spp.


The Delaware Public Health laboratory does not maintain the capabilities to analyze food for the presence of the Clostridium bacterium or its toxins (e.g., C. botulinum). These services are available at select food testing laboratories, as well as the FDA and CDC. Contact Office of Infectious Disease Epidemiology to determine need for antitoxin or if further testing is warranted. CDC Hotline can be contacted directly at (404) 639-3311.


  1. Sample collection is performed by environmental health specialists. Inquiries for specimen collection should be directed to the Office of the County Health Administrator.
    1. New Castle County - Porter State Service
    2. Kent County - James W. Williams State Service
    3. Sussex County - Georgetown State Service Center
  2. Individual (private) collections are accepted but must be arranged through environmental health personnel.
  3. Whenever possible, the epidemiologist or environmental health specialist may request an unopened can or package of the same lot/batch number along with the opened food item alleged to have been the cause of illness. Prepared food, i.e., potato salad, casseroles, can be submitted in a sterile container.
  4. Office of Infectious Disease personnel complete a detailed questionnaire regarding the history and symptoms of the illness. This will determine what testing is to be performed.
  5. A minimum portion size of 25-100 grams (1-4oz) of food collected aseptically is sufficient for testing.
  6. Complete the Request for Non-Clinical Preparedness Testing and Chain of Custody forms and submit the forms with the specimen to the laboratory or order request online through our Laboratory Information Management System (LIMS). Be sure to include pertinent patient information, as well as submitting site information with the name of the person to whom the report should be sent.
  7. Label the sample with appropriate information prior to transport to the laboratory. Ensure the sample(s) are stored/transported at specified storage temperatures for that product based on feedback from epidemiologist/laboratory personnel. Frozen foods should remain frozen and perishable foods should be refrigerated.
  8. Arrange transport to the laboratory through state health protection specialist or lab courier system.


Foods are blended and inoculated onto the appropriate selective media, incubated, and examined by lab personnel. Subcultures are performed if indicated. Organisms are confirmed with biochemical tests.


Reports are sent to the epidemiologist and environmental health specialist handling the investigation.

Turnaround times vary according to the organism being sought and range from 3 - 7 days.


Samples will be rejected if they are:

  • Unlabeled - All specimens MUST be appropriately labeled.
  • Insufficient quantity - No specimen received, no specimen in the container, or insufficient specimen to perform testing.
  • Damaged - Specimen leaked or broken in transit.
  • Improperly stored - Specimen must be maintained at proper temperature (frozen, refrigerated or room temperature) after collection and during transport to the laboratory.
  • Insufficient request information - Due to the specialized nature of food microbiology, reliable preliminary information is required prior to testing. Preauthorized and specific identification of target organism(s) is required.

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This page was last updated 3/24

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