Antimicrobial effect of lactic acid bacteria on Listeria monocytogenes isolated from cold smoked salmon

Fresh fish is easily perishable food, as a result of its specific composition and structure. The growth and development of different microorganisms, enzyme activity and biochemical changes of fish cause malfunction. Pathogen microorganism Listeria monocytogenes is often isolated from fresh fish, as well as from smoked fish and other ready-to-eat products, which are often associated with epidemics caused by L. monocytogenes. Lactic acid bacteria are of special interest, since they showed inhibitory effect against L. monocytogenes in different type of food. The aim of this study was to examine antimicrobial effect of commercial lactic acid bacteria Carnobacterium sp. (Lyoflora FP-18, SACCO) and autochthonous lactic acid bacteria (LAB) on L. monocytogenes, isolated from cold smoked salmon. L. monocytogenes was isolated from samples of cold smoked salmon according to ISO 11290-1 method for isolation and identification of L. monocytogenes. In order to identify isolated strains, Gram positive coccoide rods and catalase positive isolates were identified using biochemical characterization API Listeria and PCR method using LM1 (5‟- CCT AAG ACG CCA ATC GAA - 3‟) and LM2 (5‟- AAG CGC TTG CAA CTG CTC - 3‟) primers. Antimicrobial activity of commercial LAB Carnobacterium sp. and autochthonous LAB isolated from traditional cheeses, on isolated L. monocytogenes strains and L. monocytogenes ATCC 19111, was conducted using agar well diffusion assay. Results of API Listeria and PCR method showed that two isolates, from cold smoked salmon, were identified as L. monocytogenes. According to the results of antimicrobial activity, Carnobacterium sp. showed the highest zone of inhibition on L. monocytogenes strains, while autochthonous LAB showed slightly lower inhibition zone. Obtained results indicate that all LAB posses significant antimicrobial activity against L. monocytogenes. Furthermore, autochthonous LAB represent good candidate for further investigation on practical application in the food industry in controlling listeria contamination.