In vitro modelling of simultaneous interactions of Listeria monocytogenes, Lactobacillus sakei, and Staphylococcus carnosus.

The Jameson effect model describes suppression of microorganism growth as being dependent on non-specific competition. This model was developed for simultaneous growth in a liquid medium and microbial interactions between Listeria monocytogenes, Lactobacillus sakei, and Staphylococcus carnosus with addition of NaNO2 to mimic the manufacturing process of salami for 48 h at 21°C and then for 14 days at 17°C. L. monocytogenes in the presence of L. sakei was inhibited by 2.120 log CFU/mL in the presence of NaNO2, and 1.146 log CFU/mL without NaNO2. Inhibition of L. monocytogenes cocultured with S. carnosus was 2.248 log CFU/mL at 48 h, but after 336 h was not significantly (p>0.05) different from L. monocytogenes in mono-culture. The interspecific competition parameter (β) <1 indicated that the prevailing competition in co-cultures was intraspecific. Differentiation between 2 bacterial species interactions can be applied for use in starter cultures with pathogenic flora.