GROWTH-INHIBITION OF LISTERIA-MONOCYTOGENES BY SODIUM POLYPHOSPHATE AS AFFECTED BY POLYVALENT METAL-IONS

Sodium polyphosphate (SPP, average chain length = 13) increased the la g time of L. monocytogenes Scott A (Lm) in brain-heart infusion broth (BHI). Polyvalent metal ions (1-10 mM) reversed inhibition of Lm growt h by 0.5% SPP (nominal 3.6 mM). 10 mM Ca2+ or Mg2+, 5 mM Fe3+, 2 mM Mn 2+ or 1 mM Zn2+ added to SPP-containing BHI, pH 6.0, at 19 degrees C r esulted in growth comparable to control cultures. Fe2+ partially resto red growth; Ni2+, Co2+, Cu2+ or Al3+ were ineffective. SPP inhibited g rowth at 28 degrees C in BHI, pH 5.0, and Lm grew upon addition of Ca2 +, Mg2+ or Mn2+, but not Zn2+ or Fe3+. Addition of 0.5% SPP to mineral -rich foods, such as pureed beef, green beans or sweet potatoes, did n ot delay growth.