Potential sources of human listeriosis in Sweden

Abstract Altogether 68 Listeria monocytogenes strains belonging to serovar 1/2a isolated from human cases of listeriosis, salmon, rainbow trout and soft cheeses were further characterized to find out if these food products could be connected with human listeriosis in Sweden. Phagetyping and restriction endonuclease analysis (REA) with pulsed-field gel electrophoresis (PFGE) were used for characterization of the strains. Twenty-three strains belonging to phagovar 1 and five strains belonging to the closely related phagovar 24 were selected for REA and PFGE. L. monocytogenes isolates from two humans and two fish products shared the same PFGE pattern. The same was true for three human isolates and one salmon isolate. These findings suggest that there may be an association between human cases of listeriosis and consumption of salmon or rainbow trout. None of the soft cheese isolates were identical with the human strains.