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

The ability of propionic acid and chloride salts to inhibit Salmonella typh imurium growth was determined. Brain-heart infusion (BHl) was supplemented with 0, 250, 500, or 750 mM of potassium chloride (KCL) sodium chloride (Na Cl) or 0, 125, 250, or 375 mM of both KCl and NaCl. Propionic acid was adde d to the BHl and BHl salts to produce final concentrations of 0, 25 50, 75 mM of propionic acid. The final pH of the media was 6.5. Supplemented BHl w as inoculated with 10(3) S. typhimurium ml(-1) and incubated at 37 degrees C for 48 h. Culture absorbance was measured spectrophotometrically at 625 n m, and colony forming units (cfu) ml(-1) were enumerated on plate count aga r (PCA) BG sulfa agar (BGS), and bismuth sulfite agar (BS) Although propion ic 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 prod uced no injury that reduced the ability of the bacterium to grow on BGS or BS. Absorbance and cfu ml(-1) measurements detected inhibition of S. typhim urium growth by propionic acid and the salts. Findings indicate that the sy nergistic reaction between propionic acid and KCl or NaCl may be a useful c oncept to apply in the formulation of products designed to inhibit S, typhi murium growth. (C) 1999 Academic Press.