Yogurt containing bioactive molecules produced by Lactobacillus acidophilus La-5 exerts a protective effect against enterohemorrhagic Escherichia coli in mice

J Food Prot. 2012 Oct;75(10):1796-805. doi: 10.4315/0362-028X.JFP-11-508.


An active fraction extracted from Lactobacillus acidophilus La5 cell-free spent medium (LAla-5AF) was incorporated in a dairy matrix and tested to assess its antivirulent effect against enterohemorrhagic Escherichia coli (EHEC). Mice in experimental groups were fed for 4 days with yogurt supplemented with LAla-5AF. On the fifth day, mice were challenged with a single dose (10(7) CFU per mouse) of E. coli O157:H7. The clinical manifestations of the infection were significantly less severe in mice fed the yogurt supplemented with LAla-5AF. EHEC attachment and colonization was attenuated by LAla-5AF. Tumor necrosis factor alpha production was down-regulated, which might indicate a protective effect in the kidney during EHEC infection. To investigate the mechanisms associated with the in vivo effects observed, LAla-5AF was tested by reverse transcription real-time PCR to confirm its effects on the expression of several virulence genes of EHEC O157. The results showed that these fractions were able to down-regulate several virulence genes of EHEC, including stxB2, qseA, luxS, tir, ler, eaeA, and hlyB.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Adhesion / physiology
  • Colony Count, Microbial
  • Down-Regulation
  • Escherichia coli O157 / genetics
  • Escherichia coli O157 / growth & development*
  • Female
  • Lactobacillus acidophilus / metabolism
  • Lactobacillus acidophilus / physiology*
  • Mice
  • Mice, Inbred BALB C
  • Probiotics
  • Tumor Necrosis Factor-alpha / metabolism
  • Virulence Factors / genetics*
  • Yogurt / microbiology*


  • Tumor Necrosis Factor-alpha
  • Virulence Factors