The Step-by-Step Process for Tracing a Food Implicated in an E. coli Outbreak:
- A person experiencing the symptoms of E. coli (watery and/or bloody diarrhea, abdominal cramps, nausea, fever, vomiting, and/or body aches) goes to the doctor. The doctor makes an initial diagnosis, and stool cultures from the patient are sent to a clinical laboratory.
- Medical lab tests are done on the stool culture. If the presence of E. coli is determined by the local clinical lab, an isolate of that bacterial culture is sent to the state health department lab for further testing, including PFGE (pulse-field gel electrophoresis). The state health department lab sends the PFGE results electronically to the Centers for Disease Control and Prevention (CDC).
The DNA "fingerprint" (PFGE result) of the E. coli isolate is compared at CDC with other "fingerprint" samples. If is a match, CDC notifies - via an automated e-mail - the state health departments, along with the Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA).- When there are several isolates with the same PFGE pattern, state health departments investigate to identify a common exposure, such as a common food that was eaten. Local health department representatives, generally epidemiologists, use standard questionnaires to interview both sick and well persons. First, they want to find out where the sickened people ate, such as at home, a picnic, or a restaurant. Then they look for a common food that was eaten.
- If health officials find a sample of suspected food, testing is done to determine if the food is contaminated with E. coli and, if so, the PFGE pattern of the E. coli. If the PFGE matches those of the outbreak victims, that food is considered the source of the outbreak.
- If it is determined that the foodborne illness was due to a food item that was served at a public eating establishment, such as a restaurant, health officials interview the food workers. They use questionnaires to find out what and how foods were prepared. If there was a sick food worker on the job when sickened people ate at the restaurant, etc., health officials will get stool cultures from the food worker. If his or her PFGE matches those of the sickened people, health officials consider the worker to be the source of the contamination.
- If food found at a restaurant tests positive for E. coli and the PFGE matches the outbreak pattern, that food is considered the source of the outbreak. Even if health officials do not find food that tests positive for E. coli, a restaurant can be found liable for any illness associated with eating its food.
- Once the traceback investigation has determined the source of the outbreak, steps are taken to prevent further exposure or spread of the infection. For example, if the source is a specific food being distributed, a recall of that food will be implemented. If the source is an infected food worker, that person will be removed from any food-service duties until they have recovered and tested negative for that bacteria.
If a common food is identified , federal health officials use trace-back techniques to determine where the food came from. If the food is produce, the goal is to find the field where it came from. If the food is meat, the goal is to find the animal it came from. The trace-back stage of the investigation is the responsibility of the FDA (produce) or USDA (meat).
Subscribe RSS
