Inhibitory Effects of Bifidobacterium infantis 15697 Filtrates on the Growth of Salmonella Choleraesuis and Escherichia coli

Abstract

A study was conducted to investigate the mode of action of Bifidobacteriu m l ongum subsp. infantis ATCC 15697 culture ( B. infantis ) filtrates for inhibitory capabilities against Salmonella Choleraesuis and Escherichia coli . Filtrates were also tested for bacteriocins by examining acidic or proteinaceous properties of the inhibitory component. Additionally, B . infantis culture filtrates were used to treat raw turkey thigh meat to examine inhibition of pathogens in a food medium. When B . infantis filtrates were compared to a blend of acetic and lactic acids (at the same level produced by the bacteria, 3:2 ratio), the acid blend achieved a 40% lower inhibition rate against S . Choleraesuis and E . coli than the filtrate. Growing B . infantis on de Man-Rogosa-Sharpe agar (MRS) plus cysteine produced a filtrate with twice as much inhibitory action (measured as zones of inhibition) as filtrates prepared from cultures grown on Tripicase Peptone Yeast Extract (TPY) media. Bacterial inhibition was observed for filtrates applied to turkey thigh meat; however, this inhibition was the same as that of the acid blend. Results demonstrate that while the primary mode of action for B. infantis against other bacteria is acetic and lactic acids, another synergistic mechanism (possibly a bacteriocin) is involved.