A new type of ultrasonic washer-disinfector-sterilizer, able to clean, disinfect and sterilize most kinds of reusable medical devices, has been developed by using the ultrasonic levitation function with umbrella-shape oscillators and ozone bubbling together with sterilization carried out by silver electrolysis. We have examined the biomedical and physicochemical performance of this instrument. Prokariotic and gram-negative Escherichia coli and eukariotic Saccharomyces cerevisiae were killed by silver electrolysis in 18 min and 1 min, respectively. Prokariotic and gram-positive Geobacillus stearothermophilus and Bacillus atrophaeus, which are most resistant to autoclave and gas sterilization, respectively, were killed by silver electrolysis within 20 min. Prokariotic and gram-negative Pseudomonas aeruginosa was also killed by silver electrolysis in 10 min. The intensity distribution of the ultrasonic levitation waves was homogeneous throughout the tank. The concentration of ozone gas was 2.57 mg/ kg. The concentration of dissolved silver ions was around 0.17 mg/L. The disulfide bond in proteins was confirmed to be destroyed by silver electrolysis.
The gemini quaternary salt (gemini-QUAT) containing two pyridinium residues per molecule, 3,3'-(2,7-dioxaoctane)bis(1-decylpyridinium bromide) (3DOBP-4,10), exerted fungicidal activity against Saccharomyces cerevisiae accompanied by respiration inhibition and the cytoplasmic material leakage of ATP, magnesium, and potassium ions. We previously found that gemini-QUAT exerted bacterioclastic action against Escherichia coli by causing the rapid and abundant leakage of turbid materials from the cells. In addition, the first stage of the bacterioclastic action was the leakage of magnesium ions, outer membrane protein E, ATP, and lipopolysaccharides. Here, we investigated how the gemini-QUAT 3DOBP-4,10 exerts fungicidal action against S. cerevisiae. The results showed that that ≥ 0.4 μM 3DOBP-4,10 stopped respiration and that ≥ 3.0, 1.0 and 1.0 μM caused the leakage of cytoplasmic components ATP, magnesium and potassium ions, respectively. Scanning and transmission electron micrographs showed a preserved cell wall structure, whereas intracellular organelles were destroyed in cells incubated with 3DOBP-4,10. We postulated that 3DOBP-4,10 exerts its fungicidal action against S. cerevisiae not through cell wall destruction and protein leakage, but rather by penetrating the cell wall and disrupting the membranes of organelles.
The objective of this study was to develop a numerical, reaction-diffusion based model that predicted colony formation by taking into account the influence of nutrients, moisture (water activity), temperature, and the surface characteristics of building materials for various fungi. First, the results of fundamental experiments that measure the growth responses of colony size on culture media under various environmental conditions are presented. Second, the mathematical models that reproduce colony formation on the PDA medium and the numerical simulation intended for the experimental conditions are discussed. Fitting of the model coefficients was performed using the data of the fundamental experiments, and sensitivity analysis was executed. The mathematical models proposed depended on the nutrient concentration and the substrate softness of the surface of the construction materials, and were in reasonable agreement with the experimental data.
Quantitative separation of live cells from food samples is essential for non-culture methods to be validated. In this viewpoint, the feasibility of density gradient centrifugation (DGC) was demonstrated for the first time using samples of yellowtail meat to which Morganella morganii, a histamine producing bacterium had been added. Using a Ficoll density gradient from 50 to 10 w/v % with 10 w/v % steps, meat-free fractions of M. morganii cells were collected in 20-50 w/v % layers. The total cell collection rate ranged from 73-86 % irrespective of the cell density in the range 102-106 cells/200 µl.
The cytotoxicity of musty odor-emitting substances, geosmin (GM) and 2-methylisoborneol, at a concentration of 10 ng/L - 300mg/L was investigated using cultured mammalian cells. These two compounds exhibited no cytotoxicity in either the colony-formation of human KB cells or WST-1 assays of human -, monkey -, and dog -derived cells. These results suggest that the maximum concentration (700 ng/L) of GM found in the water of Lake Shinji is not toxic.
An advantage of vapor phase hydrogen peroxide (VPHP) is that it can readily react to form reactive free radicals, which perform the sterilization and form water and hydrogen by catalyst. Absorptive hydrophilic materials such as cellulosics hinder penetration due to hydrogen bonding and necessitate the use of hydrophobic materials, i.e., polyethylene or polypropylene, as packaging materials. The 8h TWA (time-weight-average) is 1 ppm. Hydrogen peroxide sterilization is now being used for the sterilization of gloveboxes, freeze dryers, isolators and endoscopes and so on. This paper focuses on the application of VPHP to the sterilization of the endoscopes.