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Ohtsuka K.,Saitama Prefectural Institute of Public Health | Kobayashi N.,Japan National Institute of Health Sciences | Morita Y.,Japan Institute for Environmental Sciences | Miyasaka J.,Kumamoto Prefectural Meat Hygiene Inspection Office | And 3 more authors.
Journal of the Food Hygienic Society of Japan | Year: 2014

Foodborne infections with enterohemorrhagic Escherichia coli (EHEC) related to food in each step of the cooking of a Japanese barbecue have been reported in Japan. We examined the survival of EHEC during various types of cooking on a Japanese barbecue. The number of EHEC in barbecue sauce remained stable during short-term storage at low temperature. In a series of experiments on survival of EHEC on beef during cooking on an electric griddle or a gas cooktop, the population was reduced by at least 1/1,100. Although these results suggested that EHEC are effectively killed by adequate cooking, the degree of reduction of EHEC varied among types of meat and was affected by uneven cooking. Furthermore, when the same cooking equipment was used to handle meats before and after cooking, 1/500 to 1/300,000 of EHEC population of contaminated uncooked meat cross-contaminated the cooked meat. Adequate cooking of beef, including internal organs, and use of separate cooking equipment for uncooked and cooked beef are important to avoid EHEC infection caused by Japanese barbecues. Source

Takano A.,Japan National Institute of Infectious Diseases | Nakao M.,Asahikawa Medical College | Masuzawa T.,Chiba Institute of Science | Takada N.,University of Fukui | And 18 more authors.
Journal of Clinical Microbiology | Year: 2011

Multilocus sequence typing of Borrelia garinii isolates from humans and comparison with rodent and tick isolates were performed. Fifty-nine isolates were divided into two phylogenetic groups, and an association was detected between clinical and rodent isolates, suggesting that, in Japan, human-pathogenic B. garinii comes from rodents via ticks. Copyright © 2011, American Society for Microbiology. All Rights Reserved. Source

Saitoh M.,Japan Institute for Environmental Sciences | Takeda M.,Japan National Institute of Infectious Diseases | Gotoh K.,Japan Institute for Environmental Sciences | Takeuchi F.,Japan National Institute of Infectious Diseases | And 13 more authors.
PLoS ONE | Year: 2012

We studied the molecular evolution of H gene in four prevalent Asian genotypes (D3, D5, D9, and H1) of measles virus (MeV). We estimated the evolutionary time scale of the gene by the Bayesian Markov Chain Monte Carlo (MCMC) method. In addition, we predicted the changes in structure of H protein due to selective pressures. The phylogenetic tree showed that the first division of these genotypes occurred around 1931, and further division of each type in the 1960-1970s resulted in four genotypes. The rate of molecular evolution was relatively slow (5.57×10-4 substitutions per site per year). Only two positively selected sites (F476L and Q575K) were identified in H protein, although these substitutions might not have imparted significant changes to the structure of the protein or the epitopes for phylactic antibodies. The results suggested that the prevalent Asian MeV genotypes were generated over approximately 30-40 years and H protein was well conserved. © 2012 Saitoh et al. Source

Takashita E.,Japan National Institute of Infectious Diseases | Kiso M.,Tokyo Medical University | Fujisaki S.,Japan National Institute of Infectious Diseases | Yokoyama M.,Japan National Institute of Infectious Diseases | And 78 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2015

Between September 2013 and July 2014, 2,482 influenza 2009 pandemic A(H1N1) [A(H1N1)pdm09] viruses were screened in Japan for the H275Y substitution in their neuraminidase (NA) protein, which confers cross-resistance to oseltamivir and peramivir. We found that a large cluster of the H275Y mutant virus was present prior to the main influenza season in Sapporo/Hokkaido, with the detection rate for this mutant virus reaching 29% in this area. Phylogenetic analysis suggested the clonal expansion of a single mutant virus in Sapporo/Hokkaido. To understand the reason for this large cluster, we examined the in vitro and in vivo properties of the mutant virus. We found that it grew well in cell culture, with growth comparable to that of the wild-type virus. The cluster virus also replicated well in the upper respiratory tract of ferrets and was transmitted efficiently between ferrets by way of respiratory droplets. Almost all recently circulating A(H1N1)pdm09 viruses, including the cluster virus, possessed two substitutions in NA, V241I and N369K, which are known to increase replication and transmission fitness. A structural analysis of NA predicted that a third substitution (N386K) in the NA of the cluster virus destabilized the mutant NA structure in the presence of the V241I and N369K substitutions. Our results suggest that the cluster virus retained viral fitness to spread among humans and, accordingly, caused the large cluster in Sapporo/Hokkaido. However, the mutant NA structure was less stable than that of the wild-type virus. Therefore, once the wild-type virus began to circulate in the community, the mutant virus could not compete and faded out. Copyright © 2015, American Society for Microbiology. All Rights Reserved. Source

Kushibuchi I.,Tochigi Prefectural Institute of Public Health | Kobayashi M.,Japan Institute for Environmental Sciences | Kusaka T.,Kagawa University | Tsukagoshi H.,Japan Institute for Environmental Sciences | And 15 more authors.
Infection, Genetics and Evolution | Year: 2013

We investigated the evolution of the C-terminal 3rd hypervariable region of G gene in the prevalent human respiratory syncytial virus (RSV) subgroups A (RSV-A) and B (RSV-B) in Japan in 2008-2011. Phylogenetic analysis and the evolutionary timescale was obtained by the Bayesian Markov Chain Monte Carlo method. All 38 RSV-A strains detected were classified into genotype NA1 and the 17 RSV-B strains detected belonged to genotypes BA and GB2. NA1 subdivided around 1998 in the present phylogenetic tree. Genotype BA subdivided around 1994. The evolutionary rates for RSV-A and RSV-B were estimated at 3.63×10-3 and 4.56×10-3 substitutions/site/year, respectively. The mean evolutionary rate of RSV-B was significantly faster than that of RSV-A during all seasons. The pairwise distance was relatively short (less than 0.06). In addition, some unique sites under positive selection were found. The results suggested that this region of the RSV strains rapidly evolved with some unique amino acid substitutions due to positive pressure. © 2013 Elsevier B.V. Source

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