title: The effect of urea and ammonia treatments on the survival of Salmonella spp. and Yersinia enterocolitica in pig slurry.
abstract: OBJECTIVE
  The objective of this study was to investigate the survival of Salmonella and Yersinia enterocolitica strains in pig slurry and evaluate urea and ammonia as disinfection strategies.
  
  
  RESULTS
  Salmonella Anatum, Salmonella Derby, Salmonella Typhimurium DT19 and Y. enterocolitica bioserotypes 4, O:3, 2, O:5,27 and 1A, O:6,30 were selectively marked by insertion of the plasmid, pGLO encoding for green fluorescent protein and for ampicillin resistance. Strain cocktails were inoculated into fresh pig slurry (control), slurry treated with urea [final concentration 2% w/w, (0.33 mol l(-1) )] and slurry treated with ammonia [final concentration 0.5% w/w, (0.3 mol l(-1) )] and stored at 4, 14 and 25°C. Bacterial counts were determined at regular intervals on xylose lysine deoxycholate agar (XLD), and XLD supplemented with ampicillin (0.1 mg ml(-1) ) and arabinose (0.6 mg ml(-1) ) for Salmonella and cefsulodin-irgasan-novobiocin agar (CIN) and CIN supplemented with ampicillin and arabinose for Y. enterocolitica. The pH of the control-, urea- and ammonia-treated samples ranged from 7.1 to 7.7, 8.8 to 8.9 and 8.0 to 8.3, respectively. Salmonella D(4) values ranged from 2.71 to 21.29 days, D(14) values from 2.72 to 11.62 days and D(25) values from 1.76 to 6.85 days. The equivalent D values ranges for the Y. enterocolitica strains were 3.7-19.23, 1.8-16.67 and 1.63-7.09 days, respectively. Treatment significantly (P < 0.01) affected D values with control > ammonia > urea, as did incubation temperature; 4 > 14 > 25°C.
  
  
  CONCLUSIONS
  Urea and to a lesser extent ammonia may be used to disinfect Salmonella- and/or Y. enterocolitica-contaminated pig slurry, decreasing the storage time required while increasing its fertilizer value.
  
  
  CONCLUSIONS
  This study presents data supporting the treatment of pig slurry to kill important zoonotic agents, thereby reducing environmental contamination, cross-infection of other animals and decreasing zoonotic disease in the food chain.
authors.affiliation: Teagasc Food Research Centre, Ashtown, Dublin, Ireland. declan.bolton@teagasc.ie
authors.forename: D J
authors.initials: DJ
authors.lastname: Bolton
authors.forename: C
authors.initials: C
authors.lastname: Ivory
authors.forename: D A
authors.initials: DA
authors.lastname: McDowell
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D004202:Disinfectants / Q000494:pharmacology*; D005308:Fertilizers; D008372:Manure / Q000382:microbiology; D050296:Microbial Viability; D012475:Salmonella / Q000187:drug effects*; D013552:Swine; D013696:Temperature; D014508:Urea / Q000494:pharmacology*; D015008:Yersinia enterocolitica / Q000187:drug effects*
chemical_list: D004202:Disinfectants; D005308:Fertilizers; D008372:Manure; D000641:Ammonia; D014508:Urea