Protective Effect of Lactobacillus plantarum and Lactobacillus casei used as probiotic agent against enterotoxigenic Escherichia coli in vitro and in vivo

Two isolates of Lactic acid bacteria (Lactobacillus plantarum and Lactobacillus casei) were obtained from previous study. These isolates were reidentified according to different morphological and biochemical tests. Ability of these two isolates as probiotic microorganisms were examined against enterotoxigenic E. coli (ETEC) in vitro and in vivo. Results showed that L. plantarum propagated on both Man-Rogoza-Sharp (MRS) agar and in MRS broth, for different incubation periods (18, 24, 48 and 72 hr.) under anaerobic conditions had an inhibitory effect against the ETEC grown on nutrient agar plates more than that of L. casei propagated under the same
conditions. Results also showed that the optimum period for production of probiotic compounds by both isolates was 24hr to inhibit the growth of ETEC in vitro. On the other hand it was found that the ability of these isolates to inhibit the growth of ETEC after the propagation in MRS broth is better than their ability in MRS agar. A different probiotic compounds produced by both L. plantarum and L. casei that may have the inhibitory effect was examined separately. Results showed that the organic acids were the specific compounds responsible for the inhibitory effect against ETEC.