A survey on prevalence and sources of Listeria monocytogenes in ripened and steamed cheeses from the retail market in the Czech Republic.

The aim of the study was to determine the prevalence and characteristics of Listeria monocytogenes in ripened and steamed cheeses from the retail market in the Czech Republic examined between 2007 and 2016. The examination to detect and enumerate L. monocytogenes in samples was carried out at the time of purchase and at the end of the shelf-life. The isolates recovered from the samples were characterized by serotyping, clonogrouping by polymerase chain reaction (PCR) and by macrorestriction analysis. L. monocytogenes was detected in 20 of 387 (5.2%) originally packaged cheeses from different producers. The counts of L. monocytogenes did not exceed the limit of 100 CFU·g-1 in any of the samples. L. monocytogenes was detected most frequently in blue-veined cheeses from one producer (28.9%). Probably persistent L. monocytogenes strains were found in blue-veined cheeses and smear-ripened cheeses from two producers. With respect to the fact that L. monocytogenes is able to persist in food-processing facilities, it is necessary to carry out regular monitoring of Listeria occurrence in the food-processing environment. As L. monocytogenes can multiply at refrigeration temperatures, it is necessary to set the appropriate use-by date and provide information to consumers. [ABSTRACT FROM AUTHOR]