Co-cultures of lactic acid bacteria from Brazilian foods as inhibitors of Listeria monocytogenes and Escherichia coli O157:H7 biofilm formation

Abstract

This work studies co-culture effects of Lactic Acid Bacteria (LAB) such as Lactobacillus, Lactococcus and Weissella strains on the inhibition of biofilm formation in L. monocytogenes and E. coli O157: H7. The strains were screened for biofilm inhibition as monocultures (single species) as well as in all possible combinations between one Lactococcus bacteriocin producer “bac+” (VB69 and VB94) strain and one Lactobacillus or Weissella non-bacteriocin producer “bac- “strain. Each inoculum contained the lactic acid bacteria (LAB) and pathogenic bacteria in two different ratios (1:10 and 1:100). Results indicated that absolute individual biomass production in biofilm was not enhanced when compared with those of single species biofilms. In L. monocytogenes assays (1:00 ratio) a 2-log reduction was observed for the combination of L. lactis 69 + W. viridescens 113 relative to L. lactis 69 alone and a 4-log reduction was observed relative to W. viridescens 113. On the other hand, assays against E. coli O157: H7 showed that Lb. helveticus 352 + L. lactis 94 caused a 2-log reduction after 48 h incubation, which dropped to 0.75 log units at 72 h. Our data suggest that the relationship between inoculated microorganisms and the spontaneous food microbiota could be relevant for pathogen inhibition and biofilm development.

Keywords

• Biofilm
• Co-cultures
• lactic acid bacteria
• Competition
• Pathogens
• Biopreservation