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The potential in vitro of Lactobacillus gasseri was evaluated. To do that, the susceptibility/resistance to penicillin (P), cephalothin (KF), ciprofloxacin (CIP), gentamicin (CN) and dicloxacillin (DCX) was determined. The inhibitory effect of L. gasseri and the supernatant on Y. pseudotuberculosis was studied. L. gasseri growth was studied in various stress conditions such as temperature 38oC and 45oC, pH 2.5-3.5-4.5 and 6, concentrations of 3-4 and 5% bile salts and 0.5-1 and 2% of bovine bile. In the kinetics CFU/150µl, pH, acidity, sugar consumption and protein determination on MRS and PRO mediums were determined. An analysis of peptide and lactic acid was performed using high-performance liquid chromatography. It was found that: L. gasseri was resistant to KF and DCX unlike Y. pseudotuberculosis was resistant only to DCX. L. gasseriand its supernatant inhibited the pathogenic bacteria with halos of 4 and 3 ml; growths of 3x1013 and 3x1012 CFU/150μl at 38°C and 45°C; 3x109-1,3x1010 and 3x109CFU/150μl at pH from 6-4.5 and 3.5; 2.7x1012-1.3x1012 and 2.5x1012 CFU/150μl to 3-4 and 5% bile salts; 5x1012-2.4x1012 and 3.5x1012 CFU/150μl to 0.5-1 and 2% bovine bile were observed. The exponential phase of the MRS and PRO mediums occurred at 20 and 16 hours with values of 5x1011 and 3.7x1012CFU/150μl; the pH recorded initial and final values between 5.72 to 4.6 and from 5.7 to 4.48, and initial and final rates of 0.54 to 1.32% and 0.21 to 0.90% acidity. The total consumption of sugars in the MRS and PRO mediums was 69.94 and 88.09% and 0.66 and 3.12 mg/L of protein. The supernatant recorded values of 4.80 and 5.10 g/L of lactic acid and a peptide with a concentration of 0.58 mg/ml. [ABSTRACT FROM AUTHOR]

Lactobacillus plantarum strains underwent different in vitro tests through two means which simulated physiological conditions of the digestive tract; the first was the commercial MRS broth and the second was prepared based on sugar, soy milk, milk powder and wheat bran (PRO). The maximum growth relative to kinetics parameters of fermentation, the count of microorganisms viable in plate (CFU/150 ul), tolerance to pH (2.5; 3.5; 4.5 and 6%), resistance to 38°C and 45°C temperatures, viability against bile salts (3%, 4% and 5% w/v) and bile (0.5%, 1% and 2% w/v), susceptibility to antibiotics, determination of proteins, consumption of sugars, identification of peptides and lactic acid in supernatant samples were evaluated. The exponential phase in MRS and PRO media was presented at 16 hours, with a sugar consumption of 1.71 mg/L and 1.94 mg/L, a protein value of 1.61 and 1.47 mg/L. in the MRS and PRO media. The supernatant recorded values of 6.50 and 6.80 g/L lactic acid. L. plantarum was resistant only to dicloxacillin, and presented inhibition halos on Yersinia pseudotuberculosis 6 mm and 5 mm in the supernatant; counts of 3x1011and 3x1012 CFU/150μl at 38°C and 45°C, 1x109 CFU/150μl to pH 6; 4x1010 at pH 4.5 and 1x109 CFU/150μl to pH 3.5 were obtained. Finally, it was viable to different concentrations of bile salts with values between 2x1011 and 7x1013 CFU/150μL and values between 2x1012 and 2,4x1012CFU/150μL for bovine bile. [ABSTRACT FROM AUTHOR]