Inhibition of the growth of Salmonella typhimurium ST-10 by propionic acid and chloride salts

Abstract

The ability of propionic acid and chloride salts to inhibit Salmonella typhimurium growth was determined. Brain–heart infusion (BHI) was supplemented with 0, 250, 500, or 750 m M of potassium chloride (KCl), sodium chloride (NaCl), or 0, 125, 250, or 375 m M of both KCl and NaCl. Propionic acid was added to the BHI and BHI salts to produce final concentrations of 0, 25, 50, 75 m M of propionic acid. The final pH of the media was 6·5. Supplemented BHI was inoculated with 103S. typhimurium ml−1and incubated at 37°C for 48 h. Culture absorbance was measured spectrophotometrically at 625 nm, and colony forming units (cfu) ml−1were enumerated on plate count agar (PCA), BG sulfa agar (BGS), and bismuth sulfite agar (BS). Although propionic acid, KCl, and NaCl reduced S. typhimurium growth, mixtures of propionic acid and one or both salts were more effective in inhibiting S. typhimurium growth than either substance alone. Propionic acid and chloride salts produced no injury that reduced the ability of the bacterium to grow on BGS or BS. Absorbance and cfu ml−1measurements detected inhibition of S. typhimurium growth by propionic acid and the salts. Findings indicate that the synergistic reaction between propionic acid and KCl or NaCl may be a useful concept to apply in the formulation of products designed to inhibit S. typhimurium growth.