Inhibitory Effects of Metabolites from Lactobacillus casei on Phenotypic Characteristics of Salmonella typhimurium LT2

Several studies have shown the antimicrobial activity of lactobacilli against Salmonella enterica (serotype typhimurium). The aim of this study was to evaluate the inhibitory potential of metabolites produced by probiotic culture of Lactobacillus casei against S. typhimurium and its impact on S. typhimurium motility and biofilm formation.
In order to evaluate the impact of the metabolites, L. casei cell-free culture supernatant (CFCS) was collected by centrifugation of L. casei secondary cultures. Effectiveness of the CFCS against Salmonella was evaluated by the well-diffusion method. In addition, in vitro effect of this treatment on motility in Swarm agar and biofilm formation by the bacteria was investigated.
Inhibition zone diameters of S. typhimurium were 0.83 and 12.1 mm at concentrations of 50 and 100 μl of Lactobacillus CFCS against the log4 of S. typhimurium, respectively. Moreover, CFCS treatment inhibited the motility and biofilm formation by Salmonella. Concentrations of 5% and 10% were determined as the minimum inhibitory concentrations for motility and biofilm formation by S. typhimurium. Furthermore, effectiveness of the CFCS against Salmonella was dose-dependent (P L. casei CFCS is able to inhibit the growth, motility and biofilm formation in S. typhimurium.