Biomedical subjects

Tetsuya Hayashi

Publications and source records attributed to Tetsuya Hayashi.

41 records · Page 3Linked to original sources

PubMed2002

Clonal association of Staphylococcus aureus causing bullous impetigo and the emergence of new methicillin-resistant clonal groups in Kansai district in Japan.

A molecular epidemiological analysis was performed to reveal the clonal association of Staphylococcus aureus strains isolated from patients with bullous impetigo. Pulsed-field gel electrophoresis with cluster analysis, genetic and phenotypic characterizations, and antimicrobial susceptibility profiling of 88 S. aureus strains isolated from outpatients at 4 hospitals in the Kansai district in Japan were undertaken. Three distinct clonal groups were identified: 2 of them carried the exfoliative toxin (ET) A gene (eta), and the other carried the ETB gene (etb). The former groups represent 2 eta-positive clonal groups that have not been described previously. All the strains in the more dominant eta-positive clonal group and some of the strains in the etb-positive clonal group were methicillin-resistant S. aureus (MRSA) showing borderline-to-moderate resistance to beta-lactams. These MRSA strains appear to be emerging clonal groups that have not been considered in previous epidemiological studies of ET-producing S. aureus in Japan and thus pose a significant threat for future treatment of patients with bullous impetigo and/or staphylococcal scalded-skin syndrome.

Blister↗

PubMed2002

Physical and genetic map of Enterococcus faecium ATCC19434 and demonstration of intra- and interspecific genomic diversity in enterococci.

A physical map of the Enterococcus faecium ATCC19434 chromosome was constructed by NotI, I-CeuI and Sse8387I. The chromosome was a circular DNA of 2600 kb in size, and contained six rRNA operons (rrn). The locations and orientations of the six rrn operons and 24 different determinants were mapped. Genomes of three additional E. faecium strains were also analyzed by I-CeuI digestion, and the genome sizes were found to vary from 2550 to 2995 kb. We further investigated the genome sizes and number of rrn operons in four E. faecalis, one E. avium, and one E. durans strains. The genome sizes were larger than E. faecium: 3000-3250 kb in E. faecalis, 3445 kb in E. avium, and 3070 kb in E. durans. E. avium and E. durans contained six rrn operons as in E. faecium, but all the E. faecalis strains possessed four rrn operons.

Chromosomes, Bacterial↗

PubMed2002

Complete nucleotide sequence of plasmid Rts1: implications for evolution of large plasmid genomes.

Rts1, a large conjugative plasmid originally isolated from Proteus vulgaris, is a prototype for the IncT plasmids and exhibits pleiotropic thermosensitive phenotypes. Here we report the complete nucleotide sequence of Rts1. The genome is 217,182 bp in length and contains 300 potential open reading frames (ORFs). Among these, the products of 141 ORFs, including 9 previously identified genes, displayed significant sequence similarity to known proteins. The set of genes responsible for the conjugation function of Rts1 has been identified. A broad array of genes related to diverse processes of DNA metabolism were also identified. Of particular interest was the presence of tus-like genes that could be involved in replication termination. Inspection of the overall genome organization revealed that the Rts1 genome is composed of four large modules, providing an example of modular evolution of plasmid genomes.

Bacterial Proteins↗

PubMed2002

[Genetic diversity of enterohemorrhagic Escherichia coli].

Enterohemorrhagic Escherichia coli(EHEC) causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Genomic comparison of an EHEC O157: H7 strain isolated from the Sakai outbreak and a benign laboratory strain K-12 revealed that acquisition of a large amount of foreign DNA has promoted the genetic diversification of E. coli strains. In the emergence of O157: H7, bacteriophages, in particular, played an important role. EHEC are a group of strains with several serotypes, each belonging to different E. coli lineages. Even in an O157 lineage, significant phenotypic and genetic heterogeneities are observed. Recent knowledge on the significance and the generating mechanism of such heterogeneity in EHEC strains are summarized.

Escherichia coli O157↗

PubMedDate not supplied

Pressure-independent enhancement of cardiac hypertrophy in atrial natriuretic peptide-deficient mice.

1. Homozygous deletion of the pro-atrial natriuretic peptide (Nppa) gene (ANP-/-) has been associated with both cardiac hypertrophy and salt-sensitive hypertension in mice, suggesting that cardiac hypertrophy in ANP-/- mice may be related, at least in part, to increased afterload. 2. To test the hypothesis that cardiac hypertrophy in ANP-/- mice is independent of blood pressure, male ANP-/- and wild-type ANP+/+ mice were fed a low (0.05%) or basal (0.55%) NaCl diet. Five weeks later, mean arterial pressure (MAP) was measured in conscious mice; the whole heart, atria, left and right ventricles (LV and RV, respectively), brain, lung, kidney, liver and spleen were weighed and fixed for histological analysis. Separate groups of mice were subjected to echocardiographic examination under tribromoethanol anaesthesia. 3. Mean arterial pressure and atrial, LV and RV mass were greater in ANP-/- mice than in ANP+/+ mice fed the basal salt diet. Salt depletion equalized MAP in the two genotypes, but did not alter the relative cardiac hypertrophy in ANP-/- mice. The ANP-/- mice had significant LV cardiomyocyte hypertrophy when fed either basal or low-salt diets. 4. Left ventricle chamber dimensions did not differ between genotypes, but were significantly reduced in mice fed the low-salt diet; LV posterior wall and septal thickness were greater in ANP-/- than ANP+/+ mice and were not altered by diet, indicating a concentric pattern of LV hypertrophy in ANP-/- mice. Left ventricle function (cardiac output, stroke volume, ejection fraction, circumferential wall stress and velocity of circumferential wall shortening) did not differ between strains on either diet; circumferential wall stress was reduced in the low-salt groups; other functional parameters were not altered by diet. 5. These findings indicate that ANP deletion results in cardiomyocyte hypertrophy and biventricular hypertrophy independent of blood pressure, supporting the concept that ANP has direct antihypertrophic effects in the heart.

Animals↗