Listeriosis associated with gorgonzola (Italian blue-veined cheese).

We describe a case of listeriosis in Italy associated with the consumption of cheese. Opened samples of two brands of gorgonzola (Italian blue-veined cheese; referred to as brands "B" and "C") were collected from the patient's refrigerator. Unopened samples of the brand suspected to be the source of infection (brand B) were taken from the store where the cheese had been purchased, other local stores, and the production plant. Listeria monocytogenes serotype 1/2b was isolated from the patient and from the opened and unopened cheese samples. The contamination level varied from <100 to 1,200 cfu g(-1). Molecular typing of the isolates, using both randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE), demonstrated that the isolates from the patient's refrigerator, food stores, and production-plant samples were indistinguishable from the clinical isolate. Molecular typing verified the peristence of closely related L. monocytogenes isolates in the production plant B for 5 months. The results stress the importance of developing a code of hygienic practice for preventing, limiting, and where possible, eliminating this pathogen in processed foods and of educating at-risk persons on foods likely to be contaminated.