Influence of selected LAB on L. monocytogenes during production of traditionally fermented sausages.

Within the project "Safety of traditional fermented sausages: Research on protective cultures and bacteriocins" the task of Work Package 5 (WP5) was pilot production of fermented sausages inoculated with pathogen using selected protective cultures or bacteriocins. Resulting from previous work packages, three strains of Lactobacillus sakei (I151, I154 and I155) showed bacteriocin-based antimicrobial activity against Listeria monocytogenes only. Because of that, the task 5.1. was slightly changed to production of fermented sausages inoculated with pathogen Listeria monocytogenes, together with the selected protective culture. Three protective strains, as well as the strain of L. monocytogenes, were sent by the Italian partner and used for inoculation of sausages. For the purpose of this task, three batches of the indigenous sausages were prepared according to the recipes previously described in the 1st Annual Report. Within each batch, four groups of sausages were produced: a positive control group (sausages inoculated only with L. monocytogenes), and one of the three protective strains of Lb. sakei (I151, I154 and I155). A slight advantage of the strain I151 over the other two was observed in antilisterial activity, which may suggest that three investigated starins represented just three isolates of the same bacteria. This hypothesis was supported by the results of genetic investigation of bacteriocin determinants of the isolates carried out in WP3, where it was verified that all the Italian strains are subclones of the same population. Having in mind these results, it may be suggested to use only Lb. sakei I151 as a protective starter culture in further experimental investigation.