BATCH CULTURE-GROWTH RESPONSE OF A POULTRY SALMONELLA-TYPHIMURIUM ISOLATE TO AMMONIUM-SALTS

High ammonium levels have often been associated with poultry waste. in this study we chose to examine the effect of ammonium salt on growth of salmonellae. A nalidixic acid, novobiocin, resistant primary poultr y Salmonella typhimurium isolate was grown at 37 degrees C in bicarbon ate buffered (60 mM) tryptic-soy broth containing either NH4Cl, NaCl, KCl, (NH4)(4)SO4, ammonium oxalate, ammonium acetate or NH4OH. Concent rations rested ranged from 0 to 600 mM ammonium-nitrogen and growth re sponse was measured at 37 degrees C as batch culture maximum growth ra te. NH4OH was the most inhibitory ammonium salt with a minimum inhibit ory concentration of 50 mM ammonium-nitrogen while the other ammonium salts were much less inhibitory. Based on comparison of the inhibition constant (K-i) calculated from growth rates of bacteria grown on the respective salt, S. typhimurium was least sensitive to (NH4)(2)SO4 and most sensitive to NH4OH when compared to all other growth and salt co nditions. Salmonella typhimurium was equally sensitive to nonbuffered NH4Cl, KCl and NaCl containing media. However cells that were initiall y exposed to ammonium oxalate, ammonium acetate or cells exposed to NH 4Cl and either adapted (at least 10 transfers in the same basal medium ), unadapted (less than four transfers), or grown anaerobically were m ore inhibited. If appears that the initial inhibition of Salmonella gr owth by ammonium is dependent on extracellular pH and type of ion form ing the ammonium salt, but some adaptation over time to higher concent rations may also occur. (C) 1997 Elsevier Science Ltd.