Safety aspects of bacteriocinogenic lactobacillus curvatus strains isolated from smoked salmon

Introduction: Lactobacillus curvatus is a wide spread bacterium in the natural environment and its potential in producing bacteriocins represents an important opportunity for exploration it as tools for food biopreservation. Safety assessment for presence of virulence and antibiotic resistance genes in lactic acid bacteria (LAB) is an important task to be evaluated in order to be selecting these strains as commercial beneficial cultures. Purpose: The aim of this study was to explore safety aspects of bacteriocinogenic Lb. curvatus strains based on presence and expression of genes related to the virulence factors, production of biogenic amines and antibiotic resistance. Methods: Lb. curvatus ET06, ET30 and ET31 were isolated from smoked salmon, identified based on their biochemical and genetic characteristics including PCR with species-specific primers, and characterized as bacteriocin producers against some food spoilage microorganisms and foodborne pathogens. The strains were subjected to molecular and phenotypical tests to assess the presence of more than 50 genes related to virulence factors, production of biogenic amines and antibiotic resistance. Results: Lb. curvatus ET06, ET30 and ET31 produce class IIa bacteriocins with 2.8, 3.1 and 4.5 kDa, respectively, with bactericidal activity against Staphylococcus spp., Enterococcus spp. and Listeria spp., including L. monocytogenes from various serological groups. Lb. curvatus ET06, ET30 and ET31 presented also low virulence profile, indicated by the presence of few genes related to antibiotic resistance and surface proteins, based on genetic and physiological tests. Significance: Besides all beneficial properties studied for various LAB, most considered as GRAS, special attention needs to be paid to the possible presence of virulence factors, production of biogenic amines and antibiotic resistance. Horizontal gene transfer of virulence factors between pathogenic and LAB, including probiotics is a highly possible scenario in case of uncontrolled application of probiotics or starter cultures.