Survival and adherence of antimicrobial peptide ST4SA, produced by Enterococcus mundtii, at conditions found in the human gastro-intestinal tract

The probiotic strain Enterococcus mundtii ST4SA, isolated from soy beans, produces a broad-spectrum antimicrobial peptide. The aim of this study was to determine if peptide ST4SA could withstand conditions simulating those found in the gastro-intestinal tract (GIT). Antimicrobial activity of peptide ST4SA has been monitored by growth inhibition of Enterococcus faecium on plates and leakage of beta-galactosidase from damaged cells. The ability of peptide ST4SA to adhere to target cells, which is the first step in cell destruction, has been determined by calculating the percentage of active peptide that remained in the cell-free supernatant. Seventy-five percent of peptide ST4SA adhered to E. faecium HKLHS at 37 degrees C, 88% adhered to the cells at pH 8.0 and 10.0, and 75% adhered to the cells at pH 4.0 and 6.0 at 37 degrees C. Complete adherence of peptide ST4SA to E. faecium HKLHS was recorded in the presence of 3.0%, 5.0% and 10.0% (v/v) pancreatic juice, 0.3%, 0.5% and 1.0% (v/v) oxbile and 1% (w/v) NaCl, MgCl2 and KCl. Peptide ST4SA survived conditions associated with the GIT and may be used to prevent or retard the growth of intestinal microbiota.