Incidence of Listeria monocytogenes in cheese produced in Rio de Janeiro, Brazil.

The present study evaluated the incidence of Listeria spp. in some Brazilian cheeses obtained from retail stores in Rio de Janeiro, Of 103 samples of various types of cheese examined as recommended in the Listeria isolation protocol of the Health Protection Branch of Canada, 11 (10.68%) were contaminated by Listeria monocytogenes, 13 (12.62%) by Listeria innocua, 6 (5.83%) by Listeria grayi, and 1 (0.97%) by Listeria welshimeri. A higher incidence of L. monocytogenes as observed mainly in the homemade Minas Frescal cheeses (a Brazilian soft white cheese, eaten fresh), 7 of 17 (41.17%), followed by ripened cheeses, 3 of 53 (5.67%), and industrially manufactured Frescal (Minas and Ricotta) cheeses, 1 of 33 (3.03%). Three serotypes (1/2a, 1/2b and 4b) were observed among the strains of L. monocytogenes isolated, all of them being frequently involved in outbreaks of foodborne listeriosis and sporadic cases of the disease all over the world.