Survey on the prevalence of Listeria monocytogenes in Belgian artisanal cheeses

Description of the subject. Cheese is a vector of Listeria monocytogenes. By default, European Commission imposes its absence in cheese before sales, but fixes pH and water activity thresholds below which it cannot grow. Objectives. To study pH and water activity of Belgian cheeses and the prevalence of L. monocytogenes in these products. Method. Salt content, pH and water activity of 134 cheeses were determined. Absence of L. monocytogenes in 25 g of cheese was also checked. Results. Three samples had pH or water activity under threshold values from regulation. Nevertheless, all unripened cheeses were acid in comparison with data from foreign countries. Listeria monocytogenes was isolated from 1.49% of the samples. Conclusions. Belgian artisanal cheeses could allow the growth of L. monocytogenes, and the bacterium was isolated from two samples. Further experiments should be performed to understand the fate of the pathogen in these products.