The contribution of bacteriocin to inhibition of Listeria monocytogenes by Carnobacterium piscicola strains in cold-smoked salmon systems.
OBJECTIVE
To study the importance of bacteriocin production for the antilisterial effect of a bacteriocinogenic Carnobacterium piscicola strain A9b on growth of Listeria monocytogenes in broth and cold-smoked salmon systems.


RESULTS
Acriflavin treatment of strain A9b resulted in loss of bacteriocin production and of immunity to carnobacteriocin B2. Two plasmids present in the wild-type were lost in the variant that was also more sensitive to bavaricin and leucocin A than the wild-type indicating cross-resistance to class IIa bacteriocins. The growth rate of the bac- mutant was higher than that of the wild-type at 5 and 37 degrees C but not at 25 or 30 degrees C. In salmon juice the maximum cell density of L. monocytogenes was suppressed 3 and 6 log by co-culture with C. piscicola A9b bac- and bac+, respectively, as compared with the control. Sterile filtered cultures of C. piscicola A9b bac- caused a limited suppression of the maximum cell density of L. monocytogenes similar to that observed when sterile buffer was added in equal amounts. Semi-purified carnobacteriocin B2 caused a 3.5 log decline in viable cell count after 6 day of incubation in cold-smoked salmon juice at 5 degrees C. High resistance level to carnobacteriocin B2 was observed for L. monocytogenes cells exposed to semi-purified and in situ produced carnobacteriocin B2.


CONCLUSIONS
The presence of bacteriocin production in C. piscicola enhances its inhibition of L. monocytogenes.


CONCLUSIONS
Due to the emergence of resistance, a bacteriocin negative lactic acid bacteria may be more suited for practical use as a bioprotective agent against L. monocytogenes in ready-to-eat foods.
Nilsson
L
L
Department of Seafood Research, Danish Institute for Fisheries Research, Lyngby, Denmark.
Ng
Y Y
YY
Christiansen
J N
JN
Jørgensen
B L
BL
Grótinum
D
D
Gram
L
L
D000818:Animals; D000898:Antibiosis; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000502:physiology; D001430:Bacteriocins / Q000096:biosynthesis*; D003470:Culture Media; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D007777:Lactobacillaceae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008089:Listeria monocytogenes / Q000254:growth & development*; D009154:Mutation; D012474:Salmon / Q000382:microbiology*
D001426:Bacterial Proteins; D001430:Bacteriocins; D003470:Culture Media; C086963:bacteriocin B2 protein, Carnobacterium piscicola