RESUMO
Using MRS medium, as imitating gastroenteric environments, such as low pH (1.5-4.5) and high bile salt (0.1%~0.4%), the antagonistic properties of Lactobacillus acidophilus were studied. At the same time, the antimicrobial activities on pathogenic E. coli and S. aureus in the intestinal tract and antibiotic tolerance of Lacto-bacillus acidophilus were also studied. The results indicated that Lactobacillus acidophilus survived at pH 2.5 - 4.5 after 6h culture and the living bacterial number could reach 107cfu/mL. One strain even survived at pH 1.5; that living bacterial number were above 106cfu/mL at the 0.1% -0.3% bile salt and a strain survived in 0.4% after 4h culture; that antimicrobial activities to the pathogenic E. coli and 5. aureus were obvious; and that the tolerance to Penicillin and Roxithromycin was medium and power.