The Centers for Disease Control and Prevention set up a call center system to begin making random calls this evening to residents in neighborhoods where E. coli victims have been identified.

The federal agency says the system would use random digital dialing to reach residents and compare what was eaten by people who have been sickened with what was consumed by those who have not become ill. The goal, the CDC says, is to try to identify food or foods that might be the source of the E. coli, which has sickened at least 26 people, most of them in the St. Louis area.

Meanwhile, Food and Drug Administration inspectors arrived in St. Louis today to try to help federal, state and local health investigators solve the E. coli mystery.

One suspected target of the contamination has been certain food items at local Schnucks' stores. The state health department said it got an additional 38 food samples from five Schnuck's stores last night as a result of information gathered from patient interviews.

It said the samples included: Bistro salad dressing, broccoli florets, deviled eggs, diced hard boiled eggs, honey Dijon dressing, Italian dressing, pineapple chunks, red wine vinaigrette, shredded carrots, shredded radishes, shredded zucchini, and sliced red onions.

The agency said the list also included the following packaged salads and salad bar ingredients: Bistro Chopped Salad, Fresco House Salad, Fried Chicken Salad, Garden Salad, Italian Salad, and Turkey Cobb Salad. It added that other food samples would be collected and tested as the investigation continues.

The state says it has tested 51 samples from individuals suspected of being sickened by E. coli. The number of  confirmed cases remain at 26. Twenty of them are from the St. Louis area, and at least one case has been found in Arkansas, officials said. They also said all of the samples have not been tested.       

The Missouri Department of Health and Senior Services said it already had been consulting with the FDA. It sought additional assistance after learning that some of the food products under investigation came from distributors or producers outside of Missouri.  The FDA inspectors will help inspect facilities that may have been part of the distribution chain, the state said.

Read the Beacon's earlier story below:

Local and state public health officials say they have yet to identify the source of the recent outbreak of E. coli infections in St. Louis County and surrounding areas. That might puzzle the public, but not all E. coli experts are surprised that the source continues to elude officials.

"It's a reasonably large outbreak," says Dr. Phillip Tarr, a professor of pediatrics at Washington University and an expert on E coli. "It really takes some time to figure out the vehicle (source). This is not like a church picnic outbreak where relatively few people from the community will go to a single gathering. (In that situation) you could identify it."

St. Louis County has been the site of 20 of the 26 "probable and confirmed" cases in Missouri, according to the St. Louis County Health Department.

Dr. Dolores J. Gunn, director of the County Health Department, says so far "none of the food samples we have collected have tested positive" for E. coli.  She said in a statement that the department was still interviewing those affected, inspecting food samples and sending specimens to the state health lab. In addition to the 20 cases in the county, another six confirmed cases had been found in other areas in Missouri. She said 17 of the county victims and two of the victims elsewhere in the state had been hospitalized.

As a precaution, health officials are asking doctors to consider E. coli as a cause when examining an infant, child or adult who has bloody stools, one major symptom of E. coli, as well as diarrhea, fever, nausea, vomiting and cramps.

Noting that the disease is life threatening, Gunn urged parents to be "particularly vigilant if their children have bloody diarrhea. Any child with bloody diarrhea should be taken immediately to a hospital emergency room."

The official name of E. coli is Escherichia coli. County officials say it's a large and diverse group of bacteria. While most strains are harmless, others can sicken people, causing diarrhea, urinary tract infections, respiratory illness, pneumonia, and other illnesses, the officials said in a statement.

E. Coli is spread most commonly when people eat contaminated food, consume unpasteurized (raw) milk or drink water that has not been disinfected, the officials said.              

Late today, the department issued a statement to correct what it called several media inaccuracies about the outbreak, including reports that have linked the outbreak to salad bars in Schnucks stores. The department said:

• Of the 26 people infected by E. coli that have been interviewed thus far, 20 reported having eaten something from a Schnucks (77 percent), and 17 reported having eaten something from a Schnucks salad bar (65 percent). Of those who have been infected with E. coli, 35 percent did not report eating food from a Schnucks salad bar.
• Although a portion of the investigation has been looking at Schnucks' salad bars (and salad bars in general) to see if there is any connection to the outbreak, no such link has been established. Investigators continue to examine other possibilities since nine of those affected did not report having eaten anything from a Schnucks' salad bar.

Tarr said sources or vehicles through which E. coli spread can reach across wide areas.

"If the source is not associated with an identifiable point or an unusual product, it can be very difficult for health authorities to pin down. When you think about all the dozens of things you ate in the last week and try to cross check that against everyone else, that is very, very difficult."

How health officials investigate E. coli outbreaks

(Source: Centers for Disease Control)

To find cases in an outbreak of E. coli O157 infections, public health laboratories perform a kind of "DNA fingerprinting" on E. coli O157 laboratory samples. Investigators determine whether the "DNA fingerprint" pattern of E. coli bacteria from one patient is the same as that from other patients in the outbreak and from the contaminated food. Bacteria with the same "DNA fingerprint" are likely to come from the same source. Public health officials conduct intensive investigations, including interviews with ill people, to determine if people whose infecting bacteria match by "DNA fingerprinting" are part of a common source outbreak.

A series of events occurs between the time a patient is infected and the time public health officials can determine that the patient is part of an outbreak. This means that there will be a delay between the start of illness and confirmation that a patient is part of an outbreak. Public health officials work hard to speed up the process as much as possible. The timeline is as follows:

1. Incubation time: The time from eating the contaminated food to the beginning of symptoms. For E. coli O157, this is typically 3-4 days.
2. Time to treatment: The time from the first symptom until the person seeks medical care, when a diarrhea sample is collected for laboratory testing. This time lag may be 1-5 days.
3. Time to diagnosis: The time from when a person gives a sample to when E. coli O157 is obtained from it in a laboratory. This may be 1-3 days from the time the sample is received in the laboratory.
4. Sample shipping time: The time required to ship the E. coli O157 bacteria from the laboratory to the state public health authorities that will perform "DNA fingerprinting". This may take 0-7 days depending on transportation arrangements within a state and the distance between the clinical laboratory and public health department.
5. Time to "DNA fingerprinting": The time required for the state public health authorities to perform "DNA fingerprinting" on the E. coli O157 and compare it with the outbreak pattern. Ideally this can be accomplished in 1 day. However, many public health laboratories have limited staff and space, and experience multiple emergencies at the same time. Thus, the process may take 1-4 days.

The time from the beginning of the patient's illness to the confirmation that he or she was part of an outbreak is typically about 2-3 weeks. Case counts in the midst of an outbreak investigation must be interpreted within this context.