Probiotic E. coli treatment mediates antimicrobial human β-defensin synthesis and fecal excretion in humans

摘要

Inducible epithelial human β-defensins (hBD) play an important role in intestinal barrier function. In vitro studies showed that clinically effective probiotics induce antimicrobial hBD-2. Here, we aimed to assess the in vivo effect in healthy volunteers and also addressed how defensins affect probiotic survival. Symbioflor 2 containing one strain of several viable genotypes of Escherichia coli was administered to 23 healthy individuals. After 3 weeks, fecal hBD-2 peptide was increased in 78% (mean 3.7-fold; P< 0.0001). Interestingly, the fecal hBD-2 peptide was still elevated 9 weeks after treatment (P= 0.008). In vitro studies revealed that this effect was mediated by only one out of three tested E. coli genotypes and comparable to probiotic E. coliNissle 1917 (10-to 15-fold). Functional assays showed that all tested bacteria were similarly killed by defensins allowing to speculate about a suicidal character of this effect. Defensin induction seems to be a common and important mechanism of probiotic treatment. ~