The direct antimicrobial activity of 336 samples of lactic acid bacteria, isolated from Brazilian dry fermented sausages, was evaluated in vitro against two strains of Listeria monocytogenes, using agar diffusion assay. A total of 108 strains of lactic acid bacteria showed direct inhibitory activity against at least one of the two strains of Listeria monocytogenes, probably due to production of organic acids, hydrogen peroxide, and oxygen metabolites, in addition to other substances. These 108 strains were further tested for indirect antimicrobial activity against the same strains of Listeria monocytogenes, as well as against other strains of lactic acid bacteria. Indirect antimicrobial activity was evaluated using free-cells supernatants, obtained through sterilization by microfiltration. These supernatants were treated to eliminate inhibitory substances, such as organic acids, and hydrogen peroxide by adjusting the pH and liofilization. A total of eight strains of lactic acid bacteria had indirect antimicrobial activity against a least one of the indicator microorganisms. This indirect antimicrobial activity is indicator of substance similar to bacteriocins. Three of these eight strains were characterized and identified as Lactobacillus sp.
Lactic acid bacteria; antimicrobial activity; Listeria monocytogenes; Lactobacillus sp
