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PubMed | Oita Prefectural Institute of Health and Environment, Kumamoto Prefectural Meat Inspection Office, University of Miyazaki, Toyama Institute of Health and 13 more.
Type: Journal Article | Journal: Open forum infectious diseases | Year: 2015

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection causes severe diseases such as bloody diarrhea and hemolytic uremic syndrome (HUS). Although EHEC O157:H7 strains have exhibited high genetic variability, their abilities to cause human diseases have not been fully examined.Clade typing and stx subtyping of EHEC O157:H7 strains, which were isolated in Japan during 1999-2011 from 269 HUS patients and 387 asymptomatic carriers (ACs) and showed distinct pulsed-field gel electrophoresis patterns, were performed to determine relationships between specific lineages and clinical presentation.Clades 6 and 8 strains were more frequently found among the isolates from HUS cases than those from ACs (P = .00062 for clade 6, P < .0001 for clade 8). All clade 6 strains isolated from HUS patients harbored stx2a and/or stx2c, whereas all clade 8 strains harbored either stx2a or stx2a/stx2c. However, clade 7 strains were predominantly found among the AC isolates but less frequently found among the HUS isolates, suggesting a significant association between clade 7 and AC (P < .0001). Logistic regression analysis revealed that 0-9 year old age is a significant predictor of the association between clade 8 and HUS. We also found an intact norV gene, which encodes for a nitric oxide reductase that inhibits Shiga toxin activity under anaerobic condition, in all clades 1-3 isolates but not in clades 4-8 isolates.Early detection of EHEC O157:H7 strains that belonged to clades 6/8 and harbored specific stx subtypes may be important for defining the risk of disease progression in EHEC-infected 0- to 9-year-old children.


Aikawa M.,Japan Institute for Environmental Sciences | Ohara T.,Japan National Institute of Environmental Studies | Hiraki T.,Japan Institute for Environmental Sciences | Oishi O.,Fukuoka Institute of Health Environmental | And 4 more authors.
Atmospheric Environment | Year: 2010

We found a significant geographic gradient (longitudinal and latitudinal) in the sulfate (SO4 2-) concentrations measured at multiple sites over the East Asian Pacific Rim region. Furthermore, the observed gradient was well reproduced by a regional chemical transport model. The observed and modeled SO4 2- concentrations were higher at the sites closer to the Asian continent. The concentrations of SO4 2- from China as calculated by the model also showed the fundamental features of the longitudinal/latitudinal gradient. The proportional contribution of Chinese SO4 2- to the total in Japan throughout the year was above 50-70% in the control case, using data for Chinese sulfur dioxide (SO2) emission from the Regional Emission Inventory in Asia (40-60% in the low Chinese emissions case, using Chinese SO2 emissions data from the State Environmental Protection Administration of China), with a winter maximum of approximately 65-80%, although the actual concentrations of SO4 2- from China were highest in summer. The multiple-site measurements and the model analysis strongly suggest that the SO4 2- concentrations in Japan were influenced by the outflow from the Asian continent, and this influence was greatest in the areas closer to the Asian continent. In contrast, we found no longitudinal/latitudinal gradient in SO2 concentrations; instead SO2 concentrations were significantly correlated with local SO2 emissions. Our results show that large amounts of particulate sulfate are transported over long distances from the East Asian Pacific Rim region, and consequently the SO4 2- concentrations in Japan are controlled by the transboundary outflow from the Asian continent. © 2009 Elsevier Ltd. All rights reserved.


Arizono N.,Kyoto Prefectural University of Medicine | Arizono N.,Kyoto Prefectural Institute of Public Health and Environment | Yamada M.,Kyoto Prefectural University of Medicine | Tegoshi T.,Kyoto Prefectural University of Medicine | Onishi K.,Kyoto Prefectural University of Medicine
Korean Journal of Parasitology | Year: 2012

Natural habitat fragmentation and reducing habitat quality have resulted in an increased appearance of Japanese macaques, Macaca fuscata (Gray, 1870), in suburban areas in Japan. To investigate the risk of zoonotic infections, a coprological survey of helminth eggs passed by wild Japanese macaques was carried out in 2009 and 2010 in Shiga Prefecture, Japan. Microscopic examination found helminth eggs in high prevalence, and nucleotide sequencing of DNA extracted from the eggs identified Oesophagostomum cf. aculeatum and Trichuris trichiura. A fecal culture also detected infective larvae of Strongyloides fuelleborni. These zoonotic nematodes pose a potential health issue to local people in areas frequented by Japanese macaques. © 2012, Korean Society for Parasitology.


Arizono N.,Kyoto Prefectural University of Medicine | Arizono N.,Kyoto Prefectural Institute of Public Health and Environment | Kuramochi T.,The National Museum of Nature and Science | Kagei N.,Japan National Institute of Infectious Diseases
Parasitology International | Year: 2012

Acanthocephalans of the genus Bolbosoma are intestinal parasites of marine mammals with a lifecycle similar to that of anisakid nematodes. Several cases of Bolbosoma infection in humans have been reported, but no species identification has been made. Here, we report a case of Bolbosoma infection, in which the worm was found in histological sections of the partially resected small intestine of a Japanese man. Morphological features of the worm reconstructed from serial sectioning indicated that the worm was most likely to be a sexually immature female of Bolbosoma capitatum. DNA extraction from paraffin-embedded sections and ITS1-5.8S rRNA-ITS2 sequencing showed that this species formed a monophyletic group with Bolbosoma nipponicum, and was clearly distinguishable from Corynosoma spp. or Polymorphus spp. These results may provide a reference for identifying and characterizing unknown acanthocephalans found in histological sections. © 2012 Elsevier Ireland Ltd.


Arizono N.,Kyoto Prefectural University of Medicine | Arizono N.,Kyoto Prefectural Institute of Public Health and Environment | Yamada M.,Kyoto Prefectural University of Medicine | Tegoshi T.,Kyoto Prefectural University of Medicine | Yoshikawa M.,Nara Medical University
Foodborne Pathogens and Disease | Year: 2012

Anisakiasis is one of the most common fishborne helminthic diseases in Japan, which is contracted by ingesting the larvae of the nematode Anisakis spp. carried by marine fish. Anisakis simplex sensu stricto (s.s.) and A. pegreffii are the dominant species in fish caught offshore Japan. The present study aimed to identify the anisakid species infecting Japanese patients and determine whether there is any difference in the pathogenetic potential of A. simplex (s.s.) and A. pegreffii. In total, 41 and 301 Anisakis larvae were isolated from Japanese patients and chub mackerel (Scomber japonicus), respectively; these were subjected to molecular identification using polymerase chain reaction targeted at a ribosomal DNA internal transcribed spacer region. Chub mackerel larvae were further examined for survival in artificial gastric juice (pH 1.8) for 7 days and for invasiveness on 0.75% solid agar over a 24-h interval. All clinical isolates, including those of asymptomatic, acute, and chronic infections as well as those from the stomach, small intestine, colon, and stool, were identified as A. simplex (s.s.). Chub mackerel harbored A. simplex (s.s.) and A. pegreffii larvae, together with a few larvae of other anisakid species. A. simplex (s.s.) larvae from chub mackerel tolerated the artificial gastric juice better than A. pegreffii, with 50% mortality in 2.6 and 1.4 days, respectively. In addition, A. simplex (s.s.) penetrated the agar at significantly higher rates than A. pegreffii. These results show that A. simplex (s.s.) larvae have the potential to survive acidic gastric juice to some extent and penetrate the stomach, small intestine, or colon in infected humans. © Copyright 2012, Mary Ann Liebert, Inc.


Saka M.,Kyoto Prefectural Institute of Public Health and Environment | Tada N.,Kyoto Prefectural Institute of Public Health and Environment | Kamata Y.,Japan National Institute of Health Sciences
Ecotoxicology and Environmental Safety | Year: 2012

We examined the validity of an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test) under an individual-separated exposure system, where tadpoles were individually held in small glass beakers. We first conducted a comparative rearing experiment for 28 days between this exposure system and the traditional individual-grouped exposure system, both of which held 30 tadpoles (stages 49 and 50) in dechlorinated tap water (a control solution). The former system served to reduce interindividual variability in regard to three morphological measures (developmental stage, hind limb length, and total body length). Under this system, we tested thyroxine (T4, 1. μg/L) and propylthiouracil (PTU, 75. mg/L) for 28 days of exposure. The morphological data collected at 7-day intervals indicated that significant metamorphic acceleration and retardation were consistently induced in the tadpoles exposed to T4 and PTU, respectively. In addition, the thyroid glands of the tadpoles exposed to T4 and PTU clearly exhibited atrophy and hypertrophy accompanied with severe follicular cell hyperplasia, respectively. Our results are in agreement with the historical data generated from previous studies employing the traditional exposure system, thus indicating the validity of our alternative testing protocol. © 2012 Elsevier Inc.


Saka M.,Kyoto Prefectural Institute of Public Health and Environment | Tada N.,Kyoto Prefectural Institute of Public Health and Environment | Kamata Y.,Japan National Institute of Health Sciences
Current Herpetology | Year: 2011

To demonstrate the annual ovarian cycle of a multiclutched turtle Chinemys reevesii, we quantified vitellogenin (VTG, a yolk-precursor protein) in the serum collected monthly from turtles kept in an outdoor enclosure. We also sacrificed wild adult females (one or two individuals per month) captured from a river site in Kyoto, Japan, and observed oviductal eggs and follicles assigned to five size classes: C 1 to C 5, in ascending order. The seasonal variation in the serum VTG level showed a sharp peak in late spring and a broad peak during autumn, indicating that vitellogenesis accelerated rapidly in spring, decreased in summer, increased slowly but steadily in autumn, and ceased in winter. From May to July, ovulations occurred in succession preceded by the C 4-to-C 5 growth of follicles, but without substantial growth of C 1-C 3 follicles. The vernal peak of vitellogenesis would therefore contribute largely to the sequential growth of the follicles prepared for the second and third clutches of the breeding season. In August, when the successive ovulations had been completed, no remarkable growth of C 1-C 3 follicles was observed anymore, reflecting the ovarian quiescence. Newly-formed C 1 follicles appeared in September when C 2 and C 3 follicles markedly increased in number but C 4 and C 5 follicles were still absent. In October and November, C 4 and C 5 follicles were observed again, suggesting that the follicles for the first clutch of the next breeding season reached preovulatory size before hibernation. The production and remarkable growth of follicles occurring from September to November would account for the broad peak of vitellogenesis in autumn. Thus the observed seasonal variations in the serum VTG level and follicular growth were concordant with each other. © 2011 by The Herpetological Society of Japan.


Saka M.,Kyoto Prefectural Institute of Public Health and Environment | Tada N.,Kyoto Prefectural Institute of Public Health and Environment | Kamata Y.,Japan National Institute of Health Sciences
Ecotoxicology and Environmental Safety | Year: 2013

We examined the chronic toxicity of three rice paddy herbicides (simetryn, mefenacet, and thiobencarb) using an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test under an individual-separated exposure system). Each herbicide was tested at two concentrations (1/100 and 1/10 of the 96-h LC50 value reported previously) with morphometric, gravimetric, and thyroid-histological endpoints. Simetryn caused significant retardation in growth and development at both test concentrations (0.04 and 0.40. mg/L), as indicated by significantly shorter total body lengths and hind limb lengths, smaller wet body masses, and delayed developmental stages compared to those observed in the control tadpoles. However, no clear histopathology was observed in the thyroid glands of the tadpoles exposed to simetryn. These results suggest that simetryn can act as a chemical stressor retarding tadpole growth and development without disrupting thyroid functions, even at 1/100 of the 96-h LC50 value. In addition, scoliosis near the tail base was observed in the tadpoles exposed to 0.40. mg/L of simetryn at a significantly high incidence (7/30=23.3%). Therefore, simetryn can also act as a teratogen inducing axial malformations at 1/10 of the 96-h LC50 value. During the 28 days of exposure, neither mefenacet (0.03 and 0.30 mg/L) nor thiobencarb (0.008 and 0.080 mg/L) induced any abnormalities, although the test concentrations measured immediately before the solution renewals decreased to nearly 50 percent of the nominal concentrations since day 14. Because the concentrations tested for simetryn are likely to occur in paddy water, wild anuran tadpoles in paddy water may therefore be adversely impacted by simetryn. © 2013 Elsevier Inc.


Saka M.,Kyoto Prefectural Institute of Public Health and Environment
Ecotoxicology and Environmental Safety | Year: 2010

I examined the toxicity of rice paddy herbicides simetryn, mefenacet, and thiobencarb to amphibians by conducting acute toxicity tests with tadpoles of Silurana tropicalis, which has attracted as a new model species instead of Xenopus laevis. The tadpoles at stages 49 and 50 were exposed to the herbicides at several concentrations during 96 h, and median lethal concentration (LC50) values were calculated at 24-h intervals. The LC50 values of simetryn, mefenacet, and thiobencarb were 16.9-3.70 mg/L (79.3-17.4 γM), 3.06-2.70 mg/L (10.3-9.04 γM), and 1.77-0.752 mg/L (6.85-2.92 γM), respectively. The most toxic herbicide was thiobencarb followed by mefenacet and simetryn. As for thiobencarb, the sensitivity of S. tropicalis was similar to that of X. laevis reported previously. This suggests that S. tropicalis as well as X. laevis can act as a model species in acute toxicity tests. The LC50 values of the three herbicides were very close to or at most two orders of magnitude higher than the maximum concentrations likely to occur in paddy water. Therefore, the three herbicides can be harmful to amphibian larvae living in paddy water. © 2010 Elsevier Inc.


Saka M.,Kyoto Prefectural Institute of Public Health and Environment | Tada N.,Kyoto Prefectural Institute of Public Health and Environment | Kamata Y.,Iwate University
Current Herpetology | Year: 2014

Using 55 wild-caught turtles of various sizes [straight carapace length (SCL): 35-227 mm], we estimated a time span of the subadult stage extending from the onset to completion of sexual maturation in female Mauremys reevesii from central Japan. We examined serum vitellogenin (VTG, a yolk-precursor protein) levels of the 55 turtles and thereby determined the size at the onset of sexual maturation. We also sacrificed nine of these turtles (SCL: 143-180 mm) and made anatomical observations focusing on their ovaries and oviducts in order to determine size at the completion of sexual maturation. Serum VTG was detected in all females with SCL ≥155 mm but not in any female with SCL <145 mm, thus indicating that the first vitellogenesis in M. reevesii occurs when SCL has reached around 150 mm. Of the nine turtles dissected, three (SCL: 172-180 mm) had oviductal eggs, corpora lutea, and/or enlarged follicles that would be ovulated in the next breeding season, while the other turtles (SCL: 143-168 mm) did not show any anatomical evidence of full maturity. It is therefore considered that the sexual maturation of female M. reevesii is complete when SCL has reached around 170 mm. A growth curve based on the age and SCL data of the wild-caught turtles indicated that SCLs at the onset and completion of sexual maturation (150 and 170 mm, respectively) corresponded to the ages of five and seven years, respectively. The time span of the subadult stage was therefore estimated to be two years in female M. reevesii. © 2014 by The Herpetological Society of Japan.

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