Growth response of Salmonella enterica Typhimurium in co-culture with ruminal bacterium Streptococcus bovis is influenced by time of inoculation and carbohydrate substrate

Streptococcus bovis (S. bovis) is a normal inhabitant of the gastrointestinal tract of ruminants. It has a high metabolic rate and short generation time. Under conditions of carbohydrate overload, S. bovis can outgrow other ruminal microorganisms and dramatically lower the pH of the rumen. The purpose of this study was to characterize the growth effect on foodborne Salmonella enterica Typhimurium (S. Typhimurium) in the presence of the ruminal S. bovis JB1 isolate under differing incubation conditions. When S. bovis and S. Typhimurium were inoculated simultaneously and co-cultured together in Luria–Bertani broth, growth inhibition of S. Typhimurium was observed. In minimal medium supplemented with different carbon sources, inhibition of growth of S. Typhimurium was greatest in glycerol, followed by maltose, trehalose, and glucose. When the inoculation sequence was staggered in the co-culture with an initial inoculation of S. bovis followed by a subsequent inoculation with S. Typhimurium, growth inhibition of S. Typhimurium was greater for all carbon sources. Based on these studies it appears that carbon substrate and time of inoculation influence S. Typhimurium growth in the presence of actively growing S. bovis.

► Str. bovis inhibits growth of S. Typhimurium in co-culture.
► Inhibition of S. Typhimurium is greater when Str. bovis is inoculated first.
► S. Typhimurium has a slower growth rate on glucose than does Str. Bovis.