Combined effect of temperature, water activity and salt content on the growth and gene expression of Listeria monocytogenes in a dry-cured ham model system.

The combined effect of temperature, water activity (aw) and NaCl content, usually found in dry-cured ham, on the growth and expression of the virulence and stress-related genes of Listeria monocytogenes was evaluated in a dry-cured ham model system. The highest growth of this pathogen was observed at 15 °C and, at 0.98 and 0.96 aw values. At 0.94 and 0.92 aw values, moderate NaCl levels stimulated the L. monocytogenes growth and repressed the expression of the four tested genes. At 7 °C, the expression of the plcA gene was favored while at 15 °C the hly and iap genes were activated. Preventive actions based on temperature, aw and salt content should be taken to minimise risks associated with growth and gene expression of L. monocytogenes in dry-cured ham.