Inhibition of small intestinal colonization of enterotoxigenic Escherichia coli by streptococcus faecium M74 in pigs.

Colonizing and anti E. coli activity of S. faecium M74 was tested by oral inoculation of cesarean derived, colostrum deprived piglets with Streptococcus faecium M74 and subsequently with a heat stable enterotoxin (ST) producing E. coli (O101 : K30 : K99 : NM). Enterotoxin neutralization and co-culture studies were also performed in vitro. Bacterial counts in 10 cm ileal segments, fluorescein antibody stained cryostat sections, as well as 0.5 micron sections from the ilea of the experimental pigs taken 16 hours post exposure to enterotoxic E. coli (ETEC) all indicated that S. faecium M74 could not colonize the ileum of the newborn pigs, in a single high (7 X 10(8) - 3 X 10(10)) dose either in TSB or in milk suspension, in contrast to the ETEC. However, S. faecium given in milk suspension resulted a marked decrease in ileal colonization of ETEC and in weight loss of piglets. In vitro experiments indicated that neither extracellular nor cell-bound products of S. faecium M74 could neutralise ST, but there was a significant reduction of pH in the TSB cultures of S. faecium that was accompanied by a reduction in ETEC counts of the mixed cultures.