Salmonella Typhimurium Outbreak in Clover Sprouts in Utah

Salmonella . . . Just Another Gastric Monstrosity!

Bureau of Epidemiology Utah Department of Health July 1999

"…There were two other clusters of Utah residents running off to the doctor during the month of June, also exhibiting diarrheal illnesses. Laboratory testing confirmed the presence of S. typhimurium (ST) and S. muenchen (SM) in these cases. One cluster of ST matched a strain (through PFGE analysis) associated with the consumption of alfalfa/clover sprouts. The remaining SM cases matched a strain associated with unpasteurized orange juice contaminated with the bacteria.

On Friday, May 28, 1999 the Bureau of Epidemiology was contacted by an EIS officer from the CDC's Foodborne Disease Division about four Utah residents diagnosed with ST. The bacteria isolated from these four cases had a PFGE pattern that was the same as that from 79 cases that were being investigated in Colorado. During the weeks that followed, three additional ST cases were identified with the same PFGE pattern. Preliminary case-control studies conducted in Colorado suggested that consumption of alfalfa/clover sprouts was associated with the disease. Five of the seven cases completed interviews with epidemiologists who inquired about the consumption and/or handling of sprouts. Despite the matching pattern among the seven cases, only two of them reported eating sprouts including an individual who grew alfalfa sprouts at his residence.

The CDC indicated that the implicated lot of clover sprouts originally came from an Oregon sprouter.This lot was then sold to distributors in Oklahoma and Kentucky. The lot was produced in November 1998 and shipped in January and February 1999. The Utah Department of Health's Bureau of Epidemiology was particularly interested in the source of the seeds used in the home-grown sprouts, hoping to find a connection with the Oregon sprouter. A traceback including suppliers, distributors, sellers, and growers indicated this lot of seeds was originally shipped in June of 1998. The seeds were all purchased from local growers in South Dakota. From the series of phone calls, investigators learned that it was unlikely that the individual case who enjoyed home-grown sprouts became ill from them. The other case, whose PFGE pattern matched the outbreak strain, could not identify her exact date of onset due to complications from a chronic gastrointestinal disease. Although she consumes sprouts frequently from various food establishments, she also suffers from frequent abdominal pain, nausea, and vomiting. It would, therefore, be difficult to pinpoint a date for this particular traceback."

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