Antibacterial activity of lactic acid bacteria against spoilage and pathogenic bacteria isolated from the same meat small-scale facility: 1—Screening and characterization of the antibacterial compounds

A total of 87 lactic acid bacteria (LAB) (36 Lactobacillus sakei, 22 Enterococcus faecium, 16 Lactococcus garvieae, 11 Vagococcus carniphilus and 2 Enterococcus sp.) isolated from a small-scale facility producing traditional dry sausages were screened for antagonistic activity against other LAB and some spoilage and pathogenic microorganisms, also isolated from the same processing facility, except Listeria innocua (in lieu of Listeria monocytogenes) and Escherichia coli. The final goal was to investigate LAB antibacterial activity within the facility microbial ecosystem and to select interesting strains for the role of bio-preservatives. Twenty-one Ec. faecium, 6 Vc. carniphilus, 4 Lc. garvieae, 3 Lb. sakei and 2 Enterococcus sp. were shown to inhibit the growth of some indicator microorganisms in an agar well diffusion assay. Except 2 Lb. sakei and an Enterococcus sp., all these isolates exhibited antibacterial activity against L. innocua, but only 3 Ec. faecium, 5 Vc. carniphilus and 3 Lc. garvieae displayed also antagonistic activity against Staphylococcus aureus. The 5 Vc. carniphilus isolates were also found to be inhibitory for the Gram-negative bacterium Hafnia alvei. Isolates displaying antibacterial activity against L. innocua and/or Sc. aureus were investigated for the nature of antibacterial compounds synthesized against these indicator microorganisms. Bacteriocin-like production could be detected only on agar plated in overlay assays, and was unsuccessfully researched in cell-free culture supernatant fluids under conditions that eliminate acid and hydrogen peroxide inhibition. Results also showed that a Lb. sakei isolate displayed an additional inhibitory effect by H2O2 against L. innocua. These isolates will be investigated for their ability to repress the growth of undesirable bacteria in biofilms, i.e., the real mode of bacterial attachment. This is the first report on bacteriocin-like from Vc. carniphilus and on bacteriocin-like from Lc. garvieae active against both L. innocua and Sc. aureus species