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The Delaware Public Health Laboratory provides testing to assist in identification of foodborne illness outbreaks. Foods are considered to be any raw, cooked or processed edible substance, including ice, beverages or ingredients, used or intended for use in whole or in part for human consumption.

The laboratory functions in support of the state epidemiologist and Office of Food Protection in charge of investigating tainted foods or suspected food-borne outbreaks on a referral basis only. For effective laboratory analysis, it is necessary to know the symptoms and adverse reactions attributed to consuming the suspect food as determined by the epidemiologist or environmental health specialist in order to guide the laboratory analysis. 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 medias are required for fastidious organisms, usually found in mixed flora. Communication with the laboratory prior to delivery of the specimen(s) is a MUST.

Currently there are no successfully validated methods for detection of Norovirus in foods. If Norovirus infection is suspected, stool samples can be tested for this pathogen from suspected food handlers or those persons suspected of being infected. Stools should be collected in labeled sterile leak proof containers 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 Bureau of Epidemiology (EPI)


Pathogen isolation and identification:

  • Bacillus anthracis
  • Bacillus cereus
  • Brucella spp.
  • Burkholderia spp.
  • E.coli 0157:H7
  • Francisella tularensis
  • Listeria spp.
  • Salmonella spp.
  • Shigella spp.
  • Staphylococcus aureus
  • Yersinia pestis
  • Vibrio spp. (For testing Vibrio in shellfish, please contact DNREC.)

Molecular Testing:

  • Bacillus anthracis
  • Brucella spp.
  • E.coli 0157:H7
  • Francisella tularensis.
  • Salmonella spp.
  • Yersinia pestis

Toxin identification:

  • Ricin


  • Salmonella species
  • Shigella species
  • E.coli 0157:H7 and STEC
  • Vibrio species


At present this laboratory is NOT capable of analyzing food, stool or gastric specimens for the presence of bacterial or other toxins (e.g. C. botulinum). These services are available from FDA or CDC laboratories with pre-approval. Contact State Epidemiology personnel 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 will want 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, must be collected by an environmental health specialist in a sterile container.
  4. State epidemiology 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-Clincal 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. Take care to maintain temperature of the sample at routine storage temperature for that product. Frozen foods should remain frozen and perishable foods should be refrigerated.
  8. Arrange transport to the laboratory through State health protection specalist 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 biochemicaltests.

Serotyping is performed to speciate organisms for epidemiological purposes.


Reports are sent to the epidemiologist and sanitarian handling the investigation.

Turn around 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 in 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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