On 16 January, 2014, a large-scale mass food poisoning caused by Norovirus occurred in 19 elementary schools in Hamamatsu City, Shizuoka, Japan. Of 8,027 people eaten the bread, 1,271 were infected. The causative food was determined to be bread for school meals. At the Hamamatsu City Health Environment Research Center, stool specimens of patients and food handler, and lunch ingredients were inspected for causative agent. A total of 137 of the 435 (31.5%) specimens were positive for Norovirus G II by RT-qPCR assay. Phylogenetic analysis of the capsid N/S region nucleotide sequences indicated that these strains showed a high degree of similarity (≧98%) to G II.4 Sydney 2012 variant. The bread was processed using PANSORBIN Trap Method, G II.4 was detected from 2 specimens, and the quantity of virus was 2.4E+03, 3.3E+03 copies/g each. It was estimated that the polluted bread contaminated through the finger of the worker who held Norovirus or work clothes at the time of inspection work.

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Here we examined the efficacy of freezing treatment to reduce the survival of Campylobacter jejuni/coli in chicken meat. Spike experiments showed approximately 1.9–2.3 log CFU/g reduction of C. jejuni NCTC 11168 and 81–176 strains in minced chicken meats following the freezing at -20℃ for 2 weeks. This freezing condition also induced significant reduction of bacterial detection ratio in commercially-distributed minced chicken meats that exhibited 40% positivity for Campylobacter spp. as natural contamination. Furthermore, crust freezing procedure decreased numbers of Campylobacter spp. in chicken meats and offal, compared with those in chilled chicken samples, although indicator bacterial counts did not correlate with the different treatments. Qualitative detection of Campylobacter spp. resulted that imported frozen chicken thigh samples showed only 2.2% positivity while domestically-produced chilled samples were 26.7% positive for those bacteria. Together, these data clearly indicated that freezing treatment consecutively reduced survival of the thermophilic Campylobacter in chicken meats. Practical application of this treatment would be helpful to control of this pathogen in chicken meats.

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[in Japanese]

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