Yoshiyuki Ozawa

PCR Classification of CTX-M-Type β-Lactamase Genes Identified in Clinically Isolated Gram-Negative Bacilli in Japan

ABSTRACT Of 1,456 strains isolated from 2001 to 2003 demonstrating resistance to either oxyimino-cephalosporin, 317 strains, isolated in 57 of 132 clinical facilities, were found to harbor blaCTX-M genes by PCR. Fifty-seven, 161, and 99 strains harbored blaCTX-M genes belonging to the blaCTX-M-1, blaCTX-M-2, and blaCTX-M-9 clusters, respectively.

16S rRNA Methylase–producing, Gram-Negative Pathogens, Japan

To investigate the exact isolation frequency of 16S rRNA methylase–producing, gram-negative pathogenic bacteria, we tested 87,626 clinical isolates from 169 hospitals. Twenty-six strains from 16 hospitals harbored 16S rRNA methylase genes, which suggests sparse but diffuse spread of pan-aminoglycoside–resistant microbes in Japan.

Vancomycin-resistant enterococci in humans and imported chickens in Japan.

ABSTRACT The phenotypes and genotypes of 22 VanA-type vancomycin-resistant enterococci that had been isolated in Japan were examined. The VanA resistance determinant was plasmid mediated in each of the 22 strains. Of the 22 strains, 8 were isolated from different patients and 11 and 3 were obtained from different samples of chickens imported from Thailand and France, respectively. Three of the strains that were isolated from patients and the 11 strains isolated from the Thai chickens showed high-level vancomycin resistance (MICs, 512 to 1,024 μg/ml) and low-level teicoplanin resistance (MICs, 0.5 to 4 μg/ml). Each of these strains had three amino acid substitutions in the N-terminal region of the deduced VanS sequence. L50 was converted to V, E54 was converted to Q, and Q69 was converted to H compared to the vanS gene sequence of Tn1546.

Mechanical Dispersion and Molecular Motion in Crystals of Polyethylene and Other Polymers

Dynamic mechanical loss of solution-grown polyethylene crystals is measured by the suspension method as a function of temperature and the crystalline dispersion (α dispersion) is observed above 40°C in just the same manner as in melt-grown polyethylene. In the temperature range of this dispersion, the ratio of crystal lattice constants b/a progressively changes toward that of a higher symmetry hexagonal form with increasing temperature. NMR line width of the broad component becomes gradually narrow with rising temperature in this temperature range. It is concluded from these reasons that the α dispersion of polyethylene should be ascribed to the rotational vibration of chain molecules in crystalline phase about c-axis. Similar behavior of low molecular weight paraffin crystals below the rotational transition point affords an additional confirmation of the above conclusion. Crystalline dispersions of other polymers are briefly discussed.

Effects of Bjerknes Forces on Gas-Filled Microbubble Trapping by Ultrasonic Waves.

When gas-filled microbubbles flow into an ultrasonic wavefield, the microbubbles interact with the ultrasonic waves and aggregate into large masses of bubbles. Those bubbles are trapped against the surrounding liquid flow by ultrasonic waves. In this paper, the microbubble trapping by an ultrasonic wavefield are discussed both from theoretical and experimental viewpoints. Both, the microbubble aggregation by ultrasonic-wave secondary Bjerknes force and the microbubble trapping by ultrasonic-wave primary Bjerknes force are considered. The dynamics of microbubbles inside an ultrasonic wavefield are observed using two different types of gas-filled microbubbles with corresponding mean diameters of 20 µm and 1.3 µm.

Trapping of Micrometer Size Bubbles by Ultrasonic Waves

An ultrasonic trapping method of small objects is applied to micrometer size bubbles. The experiments are carried out using an ultrasonic contrast agent of mean diameter 1.3 µm. An ultrasonic focused wave of opposite phase with frequency 5 MHz is applied to produce sequential traps for the microbubble flow. It is found that the microbubbles aggregate forming large masses of bubbles which are trapped inside the ultrasonic wave field. The effects of viscosity of the surrounding liquid are also examined.

Characterization of secondary ultrasonic waves radiated from bubbles based on small-bubble trapping pattern analysis

When a microbubble oscillates under an ultrasonic wave, the bubble radiates a secondary ultrasonic wave around it. This wave produces the secondary Bjerknes force between the neighboring bubbles and it assists in the aggregation of bubbles to make bubble clouds if the phases of the vibrations are the same. In this paper, a novel technique to characterize the secondary ultrasonic wave radiated from a bubble is proposed. This method is based on the observation of the interference fringe pattern which is produced by small bubbles trapped around the bubble of interest. A method to estimate the frequency, phase and amplitude of the secondary ultrasonic wave is discussed. Experiments are carried out for bubbles produced by an ultrasonic wave contrast agent. The results show that aggregated bubbles of a few tens of micrometers radiate approximately 7th- to 8th-order harmonic waves at 200 kPa sound pressure.

Effects of Red Blood Cells on Ultrasonic Wave Microbubble Trapping

One of the problems in microbubble trapping by ultrasonic waves when applied to in vivo experiments is the existence of red blood cells (RBCs). It is expected that the amount of microbubbles which are trapped by acoustic radiation forces decrease because the RBCs in the liquid act as obstacles when the bubbles produce the bubble clouds. In this study, the effects of RBCs on microbubble trapping are examined experimentally. The results for different RBCs concentrations are shown. The dependency of the ultrasonic wave frequency on ultrasonic wave microbubble trapping is also presented.

Measurement of Secondary Ultrasonic Waves from Microbubbles by Holographic Image Reconstruction

Oscillation of a microbubble under an ultrasonic wave produces a secondary ultrasonic wave around the bubble. In this paper, a novel method for reconstructing a secondary wave source map is proposed. A holographic method is adopted in order to derive both the amplitude and phase maps of secondary ultrasonic wave sources. Experiments are carried out using microbubbles produced by an ultrasonic wave contrast agent.