AN OUTBREAK OF LISTERIOSIS SUSPECTED TO HAVE BEEN CAUSED BY RAINBOW-TROUT

An outbreak of listeriosis in Sweden, consisting of nine cases, was in vestigated by means of molecular typing of strains from patients and s trains isolated from suspected foodstuffs, together with interviews of the patients. Listeria monocytogenes was isolated from six of the pat ients, and ail isolates were of the same clonal type. This clonal type was also isolated from a ''gravad'' rainbow trout, made by producer Y , found in the refrigerator of one of the patients. Unopened packages obtained from producer Y were also found to contain the same clonal ty pe of L. monocytogenes, Based on the interview results and the bacteri ological typing, we suspect that at least six of the nine cases were c aused by gravad or cold-smoked rainbow trout made by producer Y. To ou r knowledge, this is the first rainbow trout-borne outbreak of listeri osis ever reported.