Occurrence of Listeria monocytogenes in soft and semi-soft cheeses in retail outlets in Sweden.

Samples of 333 retail cheeses produced in or imported into Sweden were examined for the presence of Listeria monocytogenes. Listeria monocytogenes was isolated from 6% of the cheese samples. Cheeses made from raw milk were more frequently contaminated with L. monocytogenes (42%) than cheeses made from heat-treated milk (2%). The incidence of the organism in whole cheeses and pre-cut wedges was similar (6%). L. monocytogenes was only found in imported cheeses (18 from France, and one from Germany and Italy, respectively). The numbers of L. monocytogenes varied from < 1 x 10(2) to 1 x 10(5) cfu/g. All L. monocytogenes strains belonged to serogroup 1/2, except isolates from two samples that belonged to serogroup 4.