In vitro evaluation of probiotic properties of 19 strains of Lactobacillus gasseri, plantarum, acidophilus and fermentum isolated from human and food sources

In the present study, simultaneous evaluation for the survival ability of probiotic bacteria at pH 2.5, viability in the presence of pepsin-pancreatin, resistance to bile salt, Adhesion ability, bacterial resistance against antibiotic substances with measuring of minimum inhibitory concentration, auto-aggregation and co-aggregation with interference of (Escherichia coli (NCTC 12900 O157:H7), Salmonella enterica (ATCC 13076) and Listeria monocytogenes (ATTC 7644)) were investigated. In the test of Acid tolerance, it was found that all the strains except LF 55, 61 and F had high viability. Strains LF 56, LF 57, LF 55, O, F and strains LF 56, LF 57 and A7 showed that had the most resistant against pancreatin and in the presence of pepsin, respectively. Furthermore, all of the strains except La5, 52 and 49 were highly resistant to bile salts. Among the 19 strains, Lactobacillus gasseri had the highest adhesion ability (62.90%). Strain Lactobacillus plantarum LF 56 and Lactobacillus gasseri 54 C showed that had the highest potentials for auto-aggregation and co-aggregation (75.31% and 33%) on three pathogens, respectively. Several strains of Lactobacillus plantarum were sensitive to the studied antibiotic substance. However, strains M8 and M11 were resistant to Kanamycin and Chloramphenicol, and also, LF 55 and D showed high resistance against Ampicillin and Chloramphenicol, respectively. It was, moreover, found that Kanamycin, Tetracycline and Chloramphenicol had no significant influence on strains 61. It was demonstrated that Lactobacillus gasseri had medium resistance to Ampicillin, Erythromycin and Tetracycline, while Lactobacillus fermentum showed highly resistance to Ampicillin and Erythromycin. According to the results, human-isolated Lactobacillus gasseri gained the high scores in terms of probiotic properties as compared with other strains. Therefore, Lactobacillus gasseri can potentially protect epithelium tissue of intestine against pathogenic bacteria and it is a preferred candidate for prophylactic purposes, preventing of intestine infections and increasing of body immune system.