Tsutomu Asao

Osaka Prefectural Institute of Public Health, Ōsaka, Ōsaka, Japan

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Publications (7)21.04 Total impact

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    ABSTRACT: Eight VanA-type enterococcal strains were isolated from 8 of 171 domestic poultry products by using enrichment by incubation in buffered peptone water at 35 degrees C and 42 degrees C. The pulsed-field gel electrophoresis patterns of all six VanA-type Enterococcus faecalis isolates were nearly indistinguishable, indicating the presence of a specific clone in Japan.
    Applied and environmental microbiology 08/2010; 76(15):5317-20. · 3.69 Impact Factor
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    FEMS Microbiology Ecology 03/2004; 47(2):263. · 3.56 Impact Factor
  • Yuko KUMEDA, Tsutomu ASAO
    Mycotoxins 01/2004; 54(1):39-41.
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    ABSTRACT: Heteroduplex panel analysis (HPA) was previously developed for genetic identification of Aspergillus Section Flavi strains, utilizing polymerase chain reaction-amplified fragments of the internal transcribed spacer (ITS) regions of the rRNA gene. Application of HPA to a field study demonstrated that a new type of FP-1 strains belonging to Section Flavi is predominantly distributed throughout sugarcane field soil in the southernmost islands of Japan, and such a trend may also be the case in Vietnam. All of the 71 tested isolates of type FP-1 were able to produce aflatoxins B and G. The morphological observations of the type FP-1 isolates showed that a major part of them had broad interfaces with Aspergillus parasiticus and the remainder with Aspergillus flavus. Phylogenetic analysis based on the ITS sequences indicated that type FP-1 formed an independent clade positioned between A. parasiticus and A. flavus, and was more closely related to the former species. This is also the first report on the distribution of Aspergillus nomius in sugarcane field soil and/or sugarcane stems in Japan and Vietnam.
    FEMS Microbiology Ecology 07/2003; 45(3):229 - 238. · 3.56 Impact Factor
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    ABSTRACT: An extensive outbreak of staphylococcal food poisoning occurred in Kansai district in Japan. As many as 13,420 cases frequently ingested dairy products manufactured by a factory in Osaka City. The main ingredient of these dairy products was powdered skim milk manufactured by a factory in Hokkaido. Staphylococcal enterotoxin A (SEA) (< or = 0.38 ng/ml) was detected in low-fat milk and approx. 3.7 ng/g in powdered skim milk. The total intake of SEA per capita was estimated mostly at approx. 20-100 ng. The assumed attack rate was considerably lower than those reported in previous outbreaks. SEA exposed at least twice to pasteurization at 130 degrees C for 4 or 2 s retained both immunological and biological activities, although it had been partially inactivated. The present outbreak was unusual in that the thermal processes had destroyed staphylococci in milk but SEA had retained enough activity to cause intoxication.
    Epidemiology and Infection 02/2003; 130(1):33-40. · 2.87 Impact Factor
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    Y Kumeda, T Asao
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    ABSTRACT: For genetic identification of Aspergillus Section Flavi isolates and detection of intraspecific variation, we developed a novel method for heteroduplex panel analysis (HPA) utilizing fragments of the internal transcribed spacer (ITS) regions (ITS1-5.8S-ITS2) of the rRNA gene that was PCR amplified with universal primers. The method involves formation of heteroduplexes with a set of reference fragments amplified from Aspergillus flavus, A. parasiticus, A. tamarii, and A. nomius and subsequent minislab vinyl polymer gel electrophoresis. The test panel is compared with species-specific standard panels (F-1, P-1, T-1, and N-1) generated by pairwise reannealing among four reference fragments. Of 90 test panels, 89 succeeded in identifying the species and 74 were identical to one of the four standard panels. Of the 16 new panels, 11 A. flavus/A. oryzae panels were identical and typed as F-2 and 4 of 5 A. nomius panels were typed as N-2 or N-3. The other strain, A. nomius IMI 358749, was unable to identify the species because no single bands were formed with any of the four reference strains. DNA sequencing revealed that our HPA method has the highest sensitivity available and is able to detect as little as one nucleotide of diversity within the species. When Penicillium or non-Section Flavi Aspergillus was subjected to HPA, the resulting bands of heteroduplexes showed apparently lower mobility and poor heteroduplex formation. This indicates that HPA is a useful identification method without morphological observation and is suitable for rapid and inexpensive screening of large numbers of isolates. The HPA typing coincided with the taxonomy of Section Flavi and is therefore applicable as an alternative to the conventional methods (Samson, R. A., E. S. Hoekstra, J. C. Frisvad, and O. Filtenborg, p. 64-97, in Introduction to Food- and Airborne Fungi, 6th ed., 2000).
    Applied and Environmental Microbiology 10/2001; 67(9):4084-90. · 3.68 Impact Factor
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    Y Kumeda, T Asao
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    ABSTRACT: A novel genetic approach for classifying the species of Aspergillus Section Flavi is described here. This approach consists of PCR amplification of the 5.8S ribosomal DNA-intervening internal transcribed spacer regions (ITS I-5.8S-ITS II) with universal primers and of analysis of the PCR product by the principle of single-strand conformation polymorphism (SSCP). The approximately 570- to 590-bp PCR products were denatured and subjected to electrophoresis on a polyacrylamide gel supplemented with 20% formamide. The SSCP patterns of these species became more distinct by the addition of formamide to the gel and by visualization with ethidium bromide staining. A little interspecific length polymorphism among amplified ribosomal DNAs was enhanced to be detected by PCR-SSCP analysis. This analysis was capable of classifying 67 of the 68 Aspergillus Section Flavi strains tested into the following four groups, regardless of origin: A. flavus/A. oryzae, A. parasiticus/A. sojae, A. tamarii, and A. nomius. The results of restriction fragment length polymorphism analysis with PCR products of the ITS regions were consistent with those of PCR-SSCP analysis, except for A. nomius, which was not clearly differentiated from A. parasiticus/A. sojae. Nonradiolabelled PCR-SSCP analysis is inexpensive and practical to perform without special apparatus or skill and should assist in fungal morphological identification.
    Applied and Environmental Microbiology 09/1996; 62(8):2947-52. · 3.68 Impact Factor