Inhibition of in vitro growth of Shiga toxin-producing Escherichia coli O157 : H7 by probiotic Lactobacillus strains due to production of lactic acid

The inhibiting characteristics of lactic acid bacteria on Shiga toxin-produ cing Escherichia coli (STEC) O157:H7 (three strains, clinically isolated) w as investigated by using a batch fermentation system. The species such as L actobacillus casei strain Shirota or L. acidophilus YIT 0070 exert growth i nhibitory and bactericidal acitivities on STEC. The pH value and undissocia ted lactic acid (U-LA) concentration of the culture medium of STEC cocultur ed with L. casei or L. acidophilus dramatically lowered when compared with those of the control culture. The cytotoxic properties of U-LA on STEC stra in 89020087 analyzed in vitro was divided into two phases, i.e., the bacter iostatic phase (between 3.2 to 62 mM) and the bactericidal phase (over 62 m M), These data suggest that the bactericidal effect of Lactobacillus on STE C depends on its lactic acid production and pH reductive effect. (C) 2001 E lsevier Science B.V. All rights reserved.