Lactobacillus plantarum impairs the virulence potential of gram-positive and gram-negative food borne pathogens in cell cultures. - GreenMedInfo Summary

Listeria monocytogenes, Salmonella enterica and verocytotoxigenic Escherichia coli (VTEC) are among the most important agents responsible for food outbreaks occurred worldwide. In this work, two Lactobacillus spp. strains (LABs), Lactobacillus plantarum (LB95) and Lactobacillus paraplantarum (LB13) previously isolated from spontaneously fermenting olive brines, and two reference probiotic strains, Lactobacillus casei Shirota and Lactobacillus rhamnosus GG, were investigated for their abilities to attenuate the virulence of the aforementioned pathogens using animal cell culture assays. In competitive exclusion assays, the relative percentages of adhesion and invasion of S. Enteritidis were significantly reduced when the human HT-29 cell line was previously exposed to LB95. The relative percentage of invasion of L. monocytogenes was significantly reduced when the HT-29 cells were previously exposed to LB95. In the cytotoxicity assays, the cell-free supernatant of the co-culture (CFSC) of VTEC with LB95 accounted for the lowest value obtained among the co-cultures of the VTEC with the LABs, and was significantly lower than the value obtained with the co-culture of the VTEC with the two probiotic reference strains. The cytotoxicity of CFSC of VTEC with both LB95 and LB13 exhibited values not significantly different from the CFS of the nonpathogenic E. coli B strain. Our results suggest that LB95 may be able to attenuate the virulence of gram-positive and gram-negative food borne pathogens; together with other reported features of these strains, our data unfold their potential use in probiotic foods due to an interesting potential in preventing enteric infections in humans.