IAFP 2009 Program Book and Abstract Book - AB58

T8-10 Reduction in Salmonella Positives for Six USDA-FSIS Regulated Product Classes PRIYA KADAM, Gurinder Saini, Denise R. Eblen and Patty Bennett USDA/FSIS/OPHS, Washington, D.C., USA Introduction: In 2006 FSIS introduced a risk-based sampling initiative for PR/HACCP Salmonella sample scheduling. This initiative included the introduction of a risk-based algorithm to schedule Salmonella sampling, the categorization of establishments depending on the level of process control, as determined by Salmonella set results, and the introduction of PR/HACCP testing for turkey carcasses. Purpose: The numbers of Salmonella positives and the proportion of human health-hazard serotypes (HHS, as identified by CDC) were compared for the first two years of risk-based sampling (July 2006 to June 2007 (year 1-risk based:Y1RB) and July 2007 to June 2008 (year 2-risk based:Y2RB)) and the preceding year (non-risk based sampling: NRB, July 2005 to June 2006, for six product classes: cow/bull, market hog, steer/heifer, ground beef, ground chicken and ground turkey. The effect of the season of sample collection and the progress toward the goal of 90% regulated establishments in category 1, i.e., demonstrating consistent process control by 2010, were also examined. Methods: SAS software was used to extract, clean and analyze data retrieved from the FSIS Sybase data warehouse. Results: Overall there was a decline in Salmonella percent positives for all product classes, with a significant decline in ground chicken, from 52.9 % in NRB to 23.5 % in Y2RB (P < 0.05). The overall proportion of HHS did not differ significantly for any product class from year to year. However, ground chicken and turkey had the highest proportions positive for HHS for three years. Furthermore there was no seasonal variation in Salmonella percent positive samples, although HHS were significantly more common in the winter (P < 0.05). In Y2RB, 70% of the establishments were in category 1, which was a 20% increase from NRB. Significance: These data suggest that the risk-based sampling program had a positive impact, and the establishments are demonstrating progress toward consistent process control. T8-11 Effect of Autoinducer-2 on the Gene Expression of Salmonella Typhimurium PALMY R. JESUDHASAN and Suresh D. Pillai Texas A&M University, Poultry Science, College Station, TX, USA Introduction: Salmonella Typhimurium is the most common among the 2500 strains of Salmonella, the enteric pathogen that causes salmonellosis. This foodborne illness accounts for 1.3 million human illnesses due to food and 31% of food-related deaths in the United States each year. S. Typhimurium is known to use the signaling molecule called autoinducer-2 (AI-2) to communicate with other bacteria in response to external stimuli. In other bacteria, AI-2 is known to regulate various cellular processes such as biofilm formation, motility, and virulence. Understanding the role of AI-2 on the global gene expression profile of S. Typhimurium could pave the way for the use of AI-2 as a novel intervention tool. Purpose: The purpose of this study was to understand the influence of autoinducer-2 on global gene expression of S. Typhimurium. Methods: A poultry isolate, S. Typhimurium was obtained from the National Veterinary Service Laboratory, Ames, Iowa. A luxS mutant of this strain, designated PJ002 (luxS::cat), was generated. Fresh culture of PJ002 was inoculated in LB media (90%) + 10% of in vitro synthesized-AI-2 (test -1), LB media (90%) +10 % of spent culture media containing AI-2 from S. Typhimurium (test -2), LB media (90%) +10 % of spent culture media containing AI-2 from E. coli (test -3), and 10 % PBS + 90% of LB media (control) and cultured at 37°C until it reached OD 1.0. Total RNA was extracted from the samples and used for cDNA synthesis. The cDNA from control and tests was labeled with either cy3 or cy5 and hybridized on the S. Typhimurium oligo array. Arrays were subsequently analyzed, using Genepix pro 6.0 and SAS 9.1.3. Genes showing greater than 1.5 (P < 0.05) were identified as significantly differentially expressed genes. Results: AI-2 appears to control the expression of a number of key metabolic genes and other genes controlling transcription, translation, and virulence. Genes including hilA, hilC, hilD, invF, orgC, sprB within the Salmonella Pathogenicity Island -1(SP-1), a Type III secretion system involved in bacterial colonization, were down-regulated in the presence of AI-2. These genes have been previously shown to be important for colonization in poultry and beef cattle. Infectivity assays also confirmed that AI-2 reduced invasion of HeLa cells. Significance: The presence of AI-2 reduces the virulence of S. Typhimurium. Strategies to maintain high concentrations of AI-2 within the host may serve as an effective strategy to control colonization in the host. Technical 58 — Abstract Book

IAFP 2009 Program Book and Abstract Book

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