Adherent Properties and Macrophage Activation Ability of 3 Strains of Lactic Acid Bacteria

Lactic acid bacteria (LAB) must possess probiotic properties in order to be beneficial to humans and animals. The adherent properties, the acid and bile tolerance as well as the macrophage activation ability of isolated LAB strains were investigated in this study. The adhesion was analyzed following heat, acid, trypsin, and sodium periodate treatments. Production of the cytokine tumor necrosis factor-alpha (TNF-alpha) by RAW 264.7 macrophages was also measured after stimulation with heat-killed LAB strains. The viable strains of Lactobacillus fermentum AF7, L. acidophilus GG5, and L. plantarum BB9 were able to tightly adhere to the intestinal Caco-2 cells. In addition, the GG5 strain was not affected by heating, acid, trypsin, or sodium periodate treatment. However, the adhesion of strains AF7 and BB9 was reduced significantly by heating and trypsin treatment. This result suggested the GG5 and AF7 or BB9 strains had different cell-surface adherent factors. TNF-alpha production by the RAW 264.7 macrophages was induced significantly following stimulation with heat-killed LAB at 10(8) CFU/mL in a dose-dependent fashion. In addition, macrophage activity was similar whether the treatment consisted of live probiotics, or probiotics treated with heat, acid, or trypsin. However, the activity was reduced after treating with sonication. These in vitro results showed that the LAB studied possess probiotic characteristics, such as acid or bile tolerance, adherent capability, and immune activation, and may suggest that these LAB strains retain their probiotic activity as they pass through the gastrointestinal tract.