In April and May of 1998, public health officials in eleven states received an unusually high number of reports that patients receiving health care services for gastrointestinal illness had been diagnosed with Salmonella serotype Agona infections.  The number of illnesses represented an eightfold increase over the median number of Salmonella Agona cases reported in those states from 1993 to 1997.

To determine the source of the apparent ongoing Salmonella outbreak, investigators from the states and the Centers for Disease Control and Prevention (CDC) conducted a case-control study comparing individuals who had been diagnosed with Salmonella Agona with well household members.  By June 8, 1998, 55 households had been interviewed and investigators learned that a majority of cases had consumed Millville brand plain Toasted Oats cereal before becoming ill.

Testing conducted on Toasted Oats cereal resulted in one positive Salmonella culture from an open box of the cereal and two positive cultures from unopened boxes.  The pulsed field gel electrophoresis (PFGE) pattern, or “genetic fingerprint” of the Salmonella Agona isolated from the cereal was indistinguishable from that isolated from human samples.  Malt-O-Meal, the manufacturer of the cereal, issued a recall of all plain Toasted Oats cereal.

Ultimately, 209 illnesses were reported to public health officials; 47 were hospitalizations.  Salmonella Agona cases associated with consumption of Malt-O-Meal Toasted Oats cereal were reported in California, Connecticut, Idaho, Maryland, Minnesota, Nebraska, New Jersey, Oklahoma, Tennessee, and Washington.

Nearly 10 years later on April 5, 2008, Malt-O-Meal voluntarily recalled its unsweetened Puffed Rice and Puffed Wheat cereals after finding Salmonella Agona contamination during routine testing on March 24 from the same plant. The recalled products were distributed nationally and marketed under the Malt-O-Meal cereal label as well as a variety of private labels.

Following the recall, the U.S. Food and Drug Administration, the Minnesota Department of Agriculture, and the Minnesota Department of Health launched an investigation.  On April 7, PulseNet, the molecular subtyping network for foodborne disease surveillance, independently notified the CDC’s OutbreakNet Team of a cluster of human Salmonella Agona isolates with an indistinguishable PFGE pattern in multiple States.[1],[2]

On April 10, the CDC was informed by several state health departments that patients infected with the genetically identical Salmonella Agona outbreak pattern had all consumed Malt-O-Meal cereal products.  On April 11, the Minnesota State Public Health Department confirmed that the Salmonella isolated from Malt-O-Meal’s Minnesota plant was Salmonella Agona and had the same indistinguishable PFGE pattern as the isolates from ill humans from both 2008 and 1998. Additionally, both the Delaware and New York State Public Health Laboratories isolated Salmonella Agona with matching PFGE patterns from two bags of Malt-O-Meal Puffed Rice cereal.  Within one week of the Malt-O-Meal recall, the Minnesota Department of Health linked at least 21 cases of Salmonella Agona in 13 states to the cereal.

This is another it what will be a long – too long – series of outbreak investigations where we have represented consumers in what I hope will be a cautionary tale, and a learning experience, for manufacturers of food.

[1] Salmonella Agona is an uncommon serovar that comprises less than 3% of all Salmonella cases.

[2] “PFGE” stands for pulsed field gel electrophoresis.  In disease surveillance, PFGE testing is a method of determining the genetic profile of a bacterial isolate.