IAFP 2009 Program Book and Abstract Book - AB90

the laboratory, we have tested the rate of change of MLVA type under stressful conditions of low and high temperature, irradiation and long-term and short-term starvation. Results: Under these conditions some loci (e.g. Vhec1) mutated readily (10-4/generation or less), while others did not mutate at a measurable level. Repeated passage on complete media at 37, 25, 15 or 10°C showed that the mutation rate decreased as the temperature decreased. Likewise, increased temperature (43°C) caused a significant increase in mutation rate. Furthermore, exposure to UVC irradiation and sunlight increased the rate of mutation by increasing the size of insertions and deletions within the tandem repeats. However, MLVA type did not change in 28 strains re-isolated after survival for 3 months on plants. Likewise, under short-term starvation conditions in creek water for 7 days, the MLVA type also failed to change appreciably. Nevertheless, under long-term starvation conditions in which the bacteria are allowed to grow periodically, the mutation rate was elevated. Significance: Therefore, more moderate, long-term environmental stresses foster alterations of MLVA type, but if the level or duration of the stress is such that the bacteria do not replicate, MLVA type appeared stable. P1-77 Prevalence, Serotypes, and Virulence Genes of Shiga Toxin-producing Escherichia coli Isolated from Swiss Raw Milk Cheeses CLAUDIO ZWEIFEL, Nicole Giezendanner, Sabrina Corti, Gladys Krause, Jürg Danuser and Lothar Beutin University of Zurich, Institute for Food Safety and Hygiene, Vetsuisse Faculty, Zurich, Switzerland Introduction: Shiga toxin-producing Escherichia coli (STEC) are among the most important causes of foodborne diseases. Public health problems associated with the consumption of unpasteurized milk and raw milk products are documented by recent foodborne infections. Traditionally, Swiss semi-hard and hard cheese is made from raw milk, with the natural microflora responsible for enhancing desirable flavor characteristics. Purpose: The aim of this study was to assess the STEC prevalence in soft, semi-hard, and hard raw milk cheese within a three year monitoring program and to further characterize isolated strains. Methods: The 1436 cheese samples were collected at the producer level within a national sampling plan during the period of March 2006 to November 2008. Each sample was enriched in brilliant green bile broth and screened by PCR for a region conserved between stx1 and stx2. STEC strains were isolated by colony dot-blot hybridization and further characterized by serotyping, typing of Shiga toxin genes, and detection of eae and hlyA. Results: The proportion of cheese samples with stx-positive PCR results after enrichment was 3.7% in the year 2006 (n = 432), 6.3% in the year 2007 (n = 364), and 6.8% in the year 2008 (n = 640). All positive samples originated from soft and semi-hard raw milk cheeses. The 30 isolated STEC strains belonged to non-O157 serotypes, and stx2 variants dominated among these strains. Production of stx2 and stx2d2 subtypes is an indicator for severe outcome in infected patients. Three strains harbored hlyA (enterohemolysin), whereas none tested positive for the adhesion factor intimin (eae). Significance: The results obtained reinforce the importance of soft and semi-hard raw milk cheeses as potential sources and vehicles for transmission of pathogenic STEC to humans. P1-78 Efficacy of Ethanol as a Disinfectant for Inactivation of Human Noroviruses and Murine Norovirus GRACE TUNG, Helen Rawsthorne, Carrie Zapka, David Macinga and Lee-Ann Jaykus North Carolina State University, Dept. of Food, Bioprocessing and Nutrition Sciences, Raleigh, NC, USA Introduction: Human noroviruses (NoV) account for a large portion of the overall burden of foodborne disease. Studying the effects of disinfectants on NoV can lead to more effective ways of controlling the spread of illness. Purpose: The purpose of this project is to compare commonly used disinfectants with respect to their efficacy for inactivation of several NoV as evaluated by a cell culture infectivity assay and/or quantitative reverse transcription PCR (RT-qPCR). Methods: Ethanol (concentrations of 50%, 70% and 90% vol/vol) was evaluated against two representative genogroup II human NoV strains (GII.2 and GII.4) and the murine norovirus (MNV-1), a culturable surrogate. Experiments were performed in accordance with the ASTM Standard Test Method for Efficacy of Antimicrobial Agents against Viruses in Suspension (Designation: E 1052-96) using ~105 to 107 detectable units/test and a 30 s exposure period. Virus inactivation was quantified using RT-qPCR targeting the junction between the ORF1 and ORF2 (GII human NoV) and RNA polymerase region (MNV-1); infectivity assays were also performed for MNV-1. Results: Log reductions of 0.3, 3.4 and > 3.6 were observed by infectivity assay (MNV-1) after 30 sec exposures to 50, 70 and 90% ethanol, respectively. By RT-qPCR, these numbers were 0.8, 2.8 and 2.2. For the human NoV GII.2 and GII.4 strains, there was no statistically significant (P < 0.05) reduction in titer control virus where compared to virus exposed to ethanol, regardless of concentration, as evaluated by RT-qPCR. Significance: Although it appears that the human NoV is more resistant to ethanol than the MNV-1 surrogate, the absence of a cell culture model for human strains complicates conclusions. It is also possible that protection from stool accounts for the observed difference in ethanol sensitivity. Similar experiments are in progress using disinfectants with other proposed mechanisms of action. P1-79 Characterization of the Transferability of Noviruses between Foods and Representative Surfaces BLANCA I. ESCUDERO-ABARCA, Helen Rawsthorne and Lee Ann Jaykus North Carolina State University, Raleigh, NC, USA Introduction: The human noroviruses (NoV) are responsible for a large proportion of foodborne disease, and poor personal hygiene practices of infected workers is the most common route of foodborne transmission. Their low infectious dose and environmental stability undoubtedly contribute to their success as agents of foodborne disease. 90 — Abstract Book Poster

IAFP 2009 Program Book and Abstract Book

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