One factor causing the spread of bacteria in the hospital environment is transmission of bacteria via shoes. To prevent this, disrupting the spread of bacteria from contaminated areas into clean areas is very important. We experimentally produced the following 3 types of mats.(1) Water retention type mat: The part corresponding to the pile part of commercially available floor mats is made of nylon and acrylic, and polyester is used in the base to improve water retention. In addition, an indicator, which tells the remaining amount of the disinfectant was attached.(2) Paper mat: This is a bag-shaped mat that is composed of nylon and nonwoven fabric, and filled with pulp sheats (tissue-pattern) for better water retention.(3) Tank type mat: This has a water-retaining part in the central area of the mat and parts that absorb water, released from the water-retaining part, on both sides. After spraying 0.2% (w/v) benzalkonium chloride on each mat, the number of viable bacteria on the mat was serially counted. The tank-type mat showed longer term inhibition of bacterial proliferation compared with the other two types. The disinfection rate at which bacteria was eliminated from the soles of footgear (sterile filtration rate) with S.D. was 83 ±12% for the tank type, 75 ±9% for the water retention type, and 68 ±12% for the paper type mat. Since the tank type mat was superior to the other mats in not only the disinfection rate, but also in the water retention rate, it appears to be the most effective device for disrupting the infection routes.
Escherichia coli T even phages were ethanol sensitive, whereas T odd phages were ethanol tolerant. The phagecidal activities of alcohols on ethanol sensitive phages (T even, λ) were revealed to be in the order n-propanol > ethanol > methanol >> n-butanol >> n-hexanol >> noctanol. However, the those of alcohols on ethanol tolerant phages (T odd) were revealed to be in the order methanol > ethanol > n-propanol. The phagecidal activity of n-butanol (hydrophobic) increased when small amounts of hydrophilic methanol (10 and 20%, v/v), ethanol (10 and 20%, v/v) were added. The relative soluvbility curves of glucose plus Sudan III (hydrophobicity-hydrophilicity indication) were similar to the λ phagecidal activity curves of ethanol solution. The denaturation of ethanol-sensitive phage proteins with ethanol solution (50 or 70%, v/v) on SDS-polyacrylamide gel electrophoresis was associated with a loss of the plaque-forming activity of the phage. These phenomena were not observed for the ethanoltolerant phages treated with ethanol solutions. The head proteins of ethanol-tolerant phage have a greater number of hydrophobic amino acids and fewer hydrophilic amino acids, whereas those of ethanol sensitive phage have a greater number of hydrophilic amino acids and fewer hydrophobic amino acids. From these data, we suggest that the hydrophobicityhydrophilicity balance of the alcohol solution and the phage surface proteins affects the loss of the plaque-forming activity of E. coli phages by alcohol.
We investigated the death kinetics for Escherichia coli K12 cells heated at different temperatures in the presence of saturated fatty acids having short and medium alkyl-chain lengths at various concentrations. Apparent first-order death kinetics were observed with cells heated in the presence of caproic acid, caprylic acid, capric acid, or lauric acid. Values of activation enthalpy and activation entropy of the death reaction decreased with an increase in the concentration of caprylic acid, capric acid, and lauric acid, but did not decrease much for caproic acid. Also, the value of dilution coefficient decreased with increasing heating temperature for the former three fatty acids but was not noticeably temperature dependent for caproic acid. These results suggest that there are two distinct modes for the death reaction of E. coli cells heated in the presence of fatty acids and that the hydrophobicity based on the alkyl-chain length of fatty acid molecule is responsible for such a difference in the death kinetics.
The present study was performed to isolate Salmonella by plating the bead-bacteria complexes on DHL agar after immunomagnetic separation (IMS) from food and fecal samples contaminated artificially at 1 to 103 cfu/ml, and then to detect Salmonella by polymerase chain reaction (PCR) assay. With IMS, it was possible to collect Salmonella from the samples at 1 cfu /ml. Even if colonies other than Salmonella developed on the selective agar plate, only Salmonella was detected by the PCR assay using two pairs of primers for the Salmonella invA and stn genes. Also, Salmonella was completely detected within 24 h from eggs contaminated naturally with Salmonella O9 and from diarrheal stool samples of patients with Salmonella O9 or O16. This combination of IMS and PCR seems to be a useful method for rapid and sensitive detection of Salmonella in food products and fecal specimens.
We isolated a substance inhibiting the growth of lactic acid bacteria from duhat bark, which is added to “basi”, a sugar cane wine in the Philippines, and investigated its structure. By adding gelatin to the aqueous extract of duhat bark (AEDB), 63.2% of the polyphenol components in AEDB were precipitated, and the resulting supernatant lost its inhibitory activity on the growth of lactic acid bacteria. This result indicates that the inhibitory substance was the polyphenol component combining to protein. In addition, we fractionated AEDB into two fractions by ultrafiltration and investigated their inhibitory activities on the growth of lactic acid bacteria. A strong inhibitory activity was found in the fraction having molecular weight (MW) above 1× 104 containing about 53% of the polyphenol components in AEDB, indicating that the main inhibitory substance is a polyphenol component with high MW. We then separated the polyphenol components with MW above 1× 104 by ion-exclusion chromatography using CMSepharose CL-6B, and obtained a polyphenol component with inhibitory activity on the growth of lactic acid bacteria. The polyphenol component produced gallic acid, anthocyanidins of delphinidin and cyanidin, and glucose by hydrolysis with HCl, and was assumed to be condensed tannin comprised of gallic acid and leucoanthocyanin.
The mechanism of wood degradation by the soft-rot deuteromycete, Graphium sp., was investigated. One-electron oxidation activity, assayed by ethylene generation from 2-keto-4-thiomethylbutyric acid (KTBA), and phenol oxidase activity were measured in intact cultures and in Sephadex G-50 fractions from the acetone-precipitated extracellular media, with glucose or wood as the carbon source for the cultures. Both the one-electron oxidation activity and the phenol oxidase activity were higher in wood cultures than in glucose cultures. Most of the phenol oxidase activity in wood cultures appeared to derive from laccase. Most of the ethylene generation from KTBA was attributed to hydroxyl radicals, produced by a lowmolecular-weight substance in the extracellular media. This substance was composed of peptides, carbohydrates, and Fe (II), and catalyzed redox reactions between O2 and unidentified electron donors, to produce hydroxyl radicals via H2O2. It is suggested that hydroxyl radicals may produce new phenolic substructures on the lignin polymer, making it susceptible to attack by laccase. Thus, both one-electron oxidation activity and laccase activity are important in wood degradation by Graphium sp.
The effect of clove extract, a well-known natural medicine, on the production of vero-toxins by enterohemorrhagic Escherichia coil (EHEC) O157: H7 was investigated. The production of EHEC vero-toxins was inhibited by the extract of clove (0.5%, w/v). The inhibitory effect against EHEC was obtained at a concentration below the minimal inhibitory concentration of the clove extract (>1.0 %, w/v), indicating that this extract seems to act on the vero-toxinproducing cells of EHEC before vero-toxins are produced.
In this study, the growth rate of fungus was investigated under the following three types of conditions: (a) constant temperature and humidity, (b) constant relative humidity with varying temperatures, and (c) constant absolute humidity with varying temperatures. The results showed that the growth rates of Cladosporium cladosporioides IFO 6348 under conditions (b) and (c) became 1 /2 to 1 /4 of those under condition (a). Furthermore, higher growth rate was observed in the environment where the relative humidity is constant than in the environment where the absolute humidity is constant, if the temperature variations are the same in each environment. These results suggest that the method of controlling absolute humidity is more effective than the method of controlling relative humidity to protect against the growth of fungi in building environments.
Large leaf-shaped crystals of struvite (17-19 mg/100 ml) were formed by maintaining a culture supernatant of Bacillus subtilis (natto) KFP419 at 4°C for three months. Small crystals, which formed in 4 d, were white rhombic-shaped structures, and large forms consisted of a combination of many small crystals. Struvite was also formed by a non-natto organism, Bacillus subtilis IFO3026, but to a lesser extent than by KFP419. Crystal formation was not dependent on the levels of beef extract but on those of phytone. Formation of struvite by mixing in its three constituents, that is, ammonium ions, magnesium ions and phosphoric acid, was especially influenced by the concentrations of magnesium ions or phosphoric acid.
To build a database on the thermal death of microorganisms, we designed a formulated card system consisting of more than 60 items. Those items are displayed on a card on the monitor screen of a personal computer and most of the corresponding parameters for each item are selectable by clicking. Data from research papers published so far and from experiments performed under defined environmental, microbiological, and operational conditions have been collected for the database.