Date of Award
Master of Science
Veterinary Microbiology and Preventive Medicine
Veterinary Preventative Medicine
The purpose of this study was to determine the effects of lairage pen cleaning and disinfecting (C & D) procedures on prevalence of S. enterica infected swine at slaughter and antimicrobial resistance patterns of residual S. enterica isolates. A series of four field trials were conducted in a large Midwestern abattoir. Each trial consisted of a cleaned (alkaline chloride detergent) and disinfected (H₂O₂ + peracetic acid sanitizer) pen (treated) and a control pen. Intestinal lymph nodes, cecal contents, and fecal contents were collected from 45 pigs in each pen at harvest and cultured for S. enterica. In all trials, cleaning and disinfection reduced the prevalence of S. enterica positive floor swabs in the treated pen (p<0.05). In Trial 1, no significant difference in prevalence of S. enterica in pigs between treatment and control groups occurred. In Trials 2 and 3, prevalence of S. enterica was higher in pigs from treated pens vs. pigs from control group pens (91% vs. 40%, p<0.0001 and 91% vs. 24%, p<0.0001 respectively). In Trial 4, prevalence of S. enterica was lower in pigs from treated pens vs. pigs from control pens (5% vs. 42%, p<0.0001). Pen swabs were collected from each treated lairage pen before and after application of C & D procedures. Antimicrobial resistance of recovered S. enterica isolates was determined using Kirby-Bauer disk diffusion test methods and results reported as sensitive, intermediate, or resistant to tested antimicrobials. Recovered isolates clustered into 10 resistance patterns. Prevalence of S. enterica positive pen swabs and resistance pattern diversity decreased after C & D procedures. C & D procedures appeared to be non-selective in overall residual S. enterica resistance patterns. Swine lairage pen C & D procedures consistently reduce, but do not eliminate residual S. enterica organisms within lairage pens. However, reductions in prevalence of S. enterica in lairage pens do not translate into reductions in prevalence if S. enterica infected pigs held in those pens. If C & D procedures are used in lairage situations, the impact on antimicrobial resistance of remaining isolates appears to be minimal.
Peggy L. Schmidt
Schmidt, Peggy L., "Swine lairage pen cleaning and disinfecting : effects on prevalence and antimicrobial sensitivity patterns of Salmonella enterica isolates" (2004). Retrospective Theses and Dissertations. 17515.