Effects of water activity, ammonia and Corynebacterium urealyticum on the survival of Salmonella Typhimurium in sterile poultry litter

Aims: This study examined the effects of water activity (a(w)), ammonia and Corynebacterium urealyticum on the survival of Salmonella Typhimurium in sterile poultry litter. Methods and Results: Sterile poultry litter inoculated with S. Typhimurium was adjusted to pH 9.0, various a(w) levels (0.84, 0.92 and 0.96), and total ammonia nitrogen levels were increased either by the addition of ammonium sulphate or C. urealyticum inoculation with 1% urea added. All litter treatments were incubated at 30 degrees C and sampled daily for five days. Similar results were observed at each a(w) level in both experiments. At 0.84 and 0.92 a(w), S. Typhimurium populations in litter fell below 1 log CFU g(-1) within 5 days, with no significant differences between the controls and increased ammonia treatments. At 0.96 a(w), Salmonella populations treated with increased ammonia levels were significantly lower than control treatments on days 1-5. Conclusions: This study showed that C. urealyticum can produce ammonia in litter at higher a(w) levels with sufficient available urea and that the antimicrobial efficacy of ammonia is dependent on high a(w) (similar to 0.96) in litter. Significance and Impact of the Study: These results provide insights into the production of ammonia in litter, its antimicrobial efficacy in litter and the importance of a(w) in this interaction.