Food Protection Trends - November 2010 - 705

IMS linked to Real-time PCR. Samples were inoculated at low levels (1—10 CFU/sample) with Listeria spp. and L. monocytogenes. Listeria spp. were successfully isolated from pooled food samples (0.004 CFU/g) and environmental contacts samples (1 CFU/100 cm2), showing that this method has the potential to enhance HACCP and pathogen testing regimes to reduce the incidence and spread of Listeria in food plants. Patrice Chablain, from Pall GeneSystems, France, developed a multi-parametric tool for the detection and identification of the most prevalent genera and species of sporeforming bacteria in the food chain, with naturally and artificially contaminated samples. The reason for this study was the lack of diagnostic tools, the major obstacle to control of sporeformer contamination. Inclusivity and exclusivity studies have been conducted on more than 220 collected strains, mostly composed of food isolates. The Bacillus genus was systematically confirmed, while Clostridium detection could not always been confirmed on standard RCM medium, due to difficult recovery on agar medium. The development of ready-to-use multiple parametric tools enable detection, identification and traceability of 5 genera and 9 species in less than 24 h rather than quantification of a few species. A study of differentiation and speciation of vibrios by PCR of 16S-23S rRNA intergenic spacer region (ISR) was presented by Maria Hoffmann from the US Food and Drug Administration, USA. 16S rRNA gene sequencing was accomplished for all strains analyzed and Vibrio-specific PCR primers were designed to amplify 16S-23S rRNA ISR targets. Capillary gel electrophoresis was used to analyze ISR amplicons. The ISR-typing system was shown to be reliable and efficient, taking advantage of capillary electrophoresis technology, which has been proven to be effective for identification of Vibrio at the species and subspecies level. Frank Schlitt-Dittrich from Morinaga Milk Industry Co. Ltd., Japan, presented a new protocol to detect low numbers of only viable Enterobacteriaceae in inoculated pasteurized milk, using direct PCR after ethidium bromide monoazide (EMA) treatment, with the goal of minimizing time consuming and laborious culture methods. The direct PCR (DPCR) assay was applied to inoculated samples with up to 7-log CFU of viable and heat-killed bacteria. In 8 hours, viable cells of 13 Enterobacteriaceae strains were detected in milk at inoculation levels of 14 ± 8 CFU, in duplicate. Analysis time (< 8 h) was significantly shorter than with culturing methods (several days). The method could detect < 10 viable Enterobacteriaceae cells in 10 ml of milk.

T2 — Pathogens, Sanitation and Seafood Di Li and Amit Morey
“Variation in Desiccation among Salmonella Strains” was presented by Regina C. Whitemarsh from the University of Wisconsin-Madison. It was concluded that Typhimurium strain LT2 had the poorest survival. Incubation at 15°C significantly increased survival compared with survival at 30°C. Heat shock of Salmonella for an hour at 45°C prior to inoculation of low-aw solutions enhanced survival. “Effect of Crust Freezing on the Survival of Escherichia coli and Salmonella Typhimurium in Raw Poultry

Products” was presented by Byon D. Chaves-Elizondo from Clemson University. The research showed no significant difference between crust- or completely frozen products, and skin was not a critical factor in determining survival, reduction, and injury of bacteria on products. “Characterization of the Listeria monocytogenes Transcriptional Response to Synergistic Growth Inhibition by Potassium Lactate and Sodium Diacetate” presented by Matt Stasiewicz from Cornell University, discussed research showing significant interaction between lactate and diacetate treatments. Combined diacetate and lactate treatments have synergistic effects that suggest the physiological mechanisms used by L. monocytogenes to overcome the organic acid stress. In “High Pressure Inactivation of Noroviruses in Vegetables and Fruits,” Fangfei Lou from the Ohio State University talked about the effect of pressure, pH and temperature during murine norovirus inactivation and concluded that noroviruses were more effectively inactivated at 4°C than at 20°C and more sensitive to high pressure at pH 7.0 than at pH 4.0. HPP has minimal impact on the quality of fresh produce. “Phenotypic and Genotypic Characterization of Antimicrobial Resistance in Salmonella Serotypes Isolated from Retail Meats in Canada” was presented by Mueen Aslam from the Lacombe Research Centre, Canada. The study showed that the most common Salmonella serotypes identified in chicken and turkey were Heidelberg, Hadar, and Kentucky. The presence of resistance genes generally correlated with resistance phenotypes, and their prevalence differed among serotypes. “Comparison of the rfb Cluster in 16 Rare Salmonella Serotypes” presented by Matthew Ranieri from Cornell University, showed that within Salmonella serogroups sharing a common antigenic factor, there was a high degree of similarity, especially with genes related to sugar biosynthesis, and that PCR can determine serogroups for untypeable strains. The finding of a common gene, responsible for transferring O-units across the cytoplasmic membrane may provide an alternative to traditional serotyping. Mei Lok from Penn State University successfully used comK prophage junction fragment sequences to cluster epidemic clones and those associated with 2008 Canadian outbreak with respect to their origin (processing plants) and found 1998 and 2002 comK primer pairs on strains at each year but not in plant H, although this strain had comK prophage. Further research was suggested in the area of ascertaining the role of comK in colonization and persistence. xinna Zhu from Shanghai Jiao Tong University, China, presented his research on the ABC—Transporter and biofilm formation in Listeria monocytogenes. His results suggested that lm.G_1771 plays a vital role in controlling the expression of biofilm-mediating proteins, along with others, thus ultimately regulating biofilm formation. John Holah, representing Campden BRI, UK, presented some designs to minimize washroom contamination. His research focused on the placement of handwash stations, the flow of workers and the sequence in which they should enter and exit the washroom and processing hall. He also mentioned that commercial bootwashers do not fully clean the boots but with time can act as a source of contamination.

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Food Protection Trends - November 2010

Table of Contents for the Digital Edition of Food Protection Trends - November 2010