The extensive use of antibiotics to treat device-associated infections has contributed to the acceleration of the appearance of antibiotic-resistant bacteria by spreading them through contaminated hospital environments to patients (Shintani, 2003 and Shintani et al., 2004). Comprehensive research has had limited success in the reduction of device-associated infections, and usually the only therapy to treat the infections is the removal of the infected devices from patients. Recent strategies to minimize the risks of device-associated infections have focused on the following areas: good clinical practices, prudent selection of biomaterials used for device construction, and modification of device surfaces by increasing surface biocompatibility and decreasing bacterial adherence. This paper discusses from several aspects the elements of bacterial adhesion on indwelling device surfaces that may directly relate to infections and surface treatment technologies reducing the incidence of indwelling medical device-related infections.
In recent years, there has been a great demand for polymers designed with better functions that include blood and tissue compatibility (biocompatibility) and an antimicrobial activity. The surface modification of existing polymers is one of the most attractive ways to accomplish this. Treatment with plasma, gamma ray or electron beam leads to a sufficient level of activation of polymers so that specific monomers may be grafted. The extent of modification, i.e., the degree of grafting, may be easily controlled by the careful manipulation of the radiation exposure and reaction conditions. Graft modification may be carried out almost on all polymers with the creation of a desired functional chemistry both on the surface and in the bulk matrix. The grafting is applicable to almost all polymer-monomer combinations with enormous possibilities regarding physicochemical and biological characteristics to attain appropriate antimicrobial activity as well as suitable biocompatibility.
The action of sodium hypochlorite (NaOCl) solution in the cleaning of alumina (Al2O3) particles fouled with bovine serum albumin (BSA) or pectin was studied as a function of pH. The efficacy of NaOCl in the cleaning process was evaluated in the pH region where OH- alone exerted no significant action on BSA or pectin removal. The efficiency and the rate of the removal of BSA or pectin increased with increasing available chlorine concentrations and pH. The pH dependence of the efficacy of NaOCl could be explained on the basis of the equilibrium between undissociated hypochiorous acid (HOCl) and dissociated hypochlorite ion (OCl-). The efficacy of NaOCl in the removal of BSA or pectin depended on the concentration of OCl-, but not on HOCl. Size-exclusion chromatographic analysis showed that BSA molecules were partially decomposed by the action of NaOCl, whereas no significant variation in the molecular weight of pectin molecules took place. The difference between the actions of OCl- in the removal of BSA and pectin could probably be ascribed to the reactivity of OCl- with their molecules. It could be concluded that the concentration of OCl- was a major factor determining the actual NaOCI concentration required for an efficient cleaning treatment.
method and 96-well microbioassay system with a liquid culture system. These lactones fungicidally inhibited their growth because their minimum fungicidal concentrations were only 2 to 4 times that of their minimum inhibitory concentrations. Results obtained from their structure-fungicidal activity against two species of fungi were as follows: γ-lactones exhibit higher antifungal activity than δ-lactones; the antimicrobial effects of γ-lactones are intensified as the side chain length increases; massoialactone with an unsaturated δ-lactone ring gives a smaller minimum inhibitory concentration against the two types of fungi compared with γ-and δ-decalactones; and the (R)-forms of γ-undecalactone and γ-dodecalactone inhibit the growth of A. niger at smaller concentrations compared with the (S)-forms. Vaporized massoialactone inhibited the growth of the two fungi at 1.2μg/ml in a sealed vial, whereas the γ- and δ-decalactones exhibited no inhibition against the growth of the two fungi. Massoialactone arrested the oxygen consumption byC. albicansat 240 μM, suggesting that the antimicrobial mechanism responsible for massoialactone activity againstC. albicansmay be the inhibition of the respiratory system. The reproduction of influenza virus A was inhibited at 23 and 57% by massoialactone and δ-decalactone at 0.25 and 2.5 μg/ml, respectively.
The purpose of this study is to investigate the spinnability, biodegradability and antibacterial properties of biodegradable polymers containing a silver-based antibacterial agent. The biodegradable polymers used were polybutyrene succinate (PBS) and polylactic acid (PLA). Two types of silver-based antibacterial agents, silver-based zeolite (AgZL) and silver-based zirconium phosphate (AgZR), were used. The experimental results show that the value of the weight-average molecular weight (Mw), which greatly affects the spinnability of the fiber sample, decreases with the increase in the contents of AgZL and AgZR for both PLA and PBS. The degree of the decrease in the Mw for AgZL was greater than that for AgZR because of the higher content of crystal water for AgZL. The value of antibacterial activity (R) for PLA was higher than that for PBS because of the lactic acid of PLA. AgZL was more effective in terms of antibacterial activity than AgZR in PLA and PBS fiber samples because the elution concentration of silver ions of AgZL is higher than that of AgZR from the initial stage of elution. The biodegradability of PLA and PBS increases with the increase in the content of the antibacterial agent. Especially, the hydrolysis of PLA is accelerated by the silver-based antibacterial agent. Finally, the value of R decreases as the number of washing cycles increases because the antibacterial agent falls of from the polymer surface.
Template DNA from Brevibaciiius brevis, Geobaciiius stearothermophilus, Paenibaciiius macerans, P. polymyxa and 10 species of Bacillus was used with the commercially available RAPD Analysis Primers to generate DNA fragments by PCR. Different RAPD band patterns were generated from the DNA of 14 different Bacillus species and related genera with Primer 1 or 4. The result suggested that the single use of Primer 1 or 4 is effective for the simple identification of these strains of Bacillus and related genera by the RAPD analysis. By the RAPD analyses of the template DNA prepared from bacterial colonies formed on nutrient agar plates after cultivation at 35°C for 24 to 48 h, B. brevis, B. circulans, B. firmus, B. iicheniformis, P. macerans, P. polymyxa, B. pumilus, B. sphaericus, B. subtilis and B. thuringiensis were identified by the combination of the present RAPD analysis using Primer 4 and morphological observations of colonies, vegetative cells and spores. For identification of B. coagulans and G. stearothermophilus, the RAPD analyses of the template DNA prepared from colonies formed on standard plate agar after cultivation at 55°C for 24 to 48 h might be effective though further improvements of the assay are required for identification of these Bacillus species. For simple identification of B. cereus and B. megaterium by the PCR-based method, the use of other RAPD primers or a specific PCR primer set should be developed in addition to morphological observations of colonies, vegetative cells and spores.
In order to develop a bactericidal agent which can operate under visible-light irradiation, silica gel-supported dihydroxo (tetraphenylporphyrinato) antimony (V) catalyst (SbTPP/Sio2) was prepared. Experiments to reduce concentrations of Legionella species were performed using a cylindrical SbTPP/SiO2-photocatalytic bactericidal apparatus in a cooling tower which held 8ooL of water. After 10 days, the concentrations of Legionella species were reduced to less than the detection limit, and these levels were kept until the irradiation was stopped. Also, a photocatalytic bactericidal experiment was conducted with a fountain that was filled with 13m3of water. The concentrations of Legionella species were reduced to less than the detection limit 12 days after the SbTPP/SiO2catalyst was installed in the fountain receiving sunlight irradiation. The concentrations of Legionella species were kept at less than 30CFU/100ml for 3 months until the catalyst was removed from the fountain. Thus, visible-light irradiation of the SbTPP/SiO2 catalyst induced a remarkable bactericidal activity against Legionella species in the living environment.
Bacillus subtilis spores pretreated at various water activities (aw, from 0.005 to 0.996) were inactivated by infrared radiation heating (IRH) at 0.5 and 1.0 kW of electric power under dry conditions in an open system. The resistance of B. subtilis spores to IRH was greater in the range of 0.25 to 0.874 aw, and had the maximum value when aw was 0.796 at 0.5 kW and 0.688 at 1.0 kW. Markedly lower IRH resistance of B. subtilis spores was observed at the lower or higher levels of aw.
A kinetic analysis was done for the genetic transformation of Escherichia coil DH5 α with plasmid DNA. Transformation frequency, defined as a ratio of the number of transformants to the total number of viable cells, was correlated with temperature according to Arrhenius' equation, giving a kinetic parameter of energy change associated with the reaction, ΔU. The parameter YNT, 273, defined as the plasmid-based yield of transformation at 273 K, was also proposed to evaluate the transformation process in a quantitative manner. It was found that both the values of ΔU and YNT, 273 were smaller when plasmids with larger molecular weight were used as the DNA donors. This was attributed to the unstable state of large-size plasmid DNA in the periplasmic space of the recipient cells. The coexistence of chromosome DNA as an impurity mainly caused the reduction in the YNT, 273 value without a notable drop in the ΔU value, reflecting a competitive reaction between the plasmid and chromosome DNA molecules for receptor sites on the cell surfaces.
A rapid and simple procedure for the specific detection of Salmonella was developed by using a dissolved oxygen measurement device (DOX-96) with anti-Salmonella antibodies. In the DOX-96 system, a gold electrode is located at the bottom of each well, in a 96-hole plate. The gold electrode acts as the working electrode. The anti-Salmonella antibodies are then introduced into the system and immobilized on each well of the plate. Wells contained bound Salmonella Typhimurium cells which were incubated at 37°C, and the oxygen consumption in each well was monitored. It appeared that the oxygen consumption curve was inversely proportional to the growth of S. Typhimurium. In the present method, S. Typhimurium cells with an initial concentration of 2.5 ×10 0-2.5 ×108CFU/ml in the sample showed an oxygen consumption curve within 13 h of incubation. Other microorganisms, such as Escherichia coli, Pseudomonas aeruginosa, Corynebacterium aquaticum and Bacillus subtilis did not interfere with the assay system. Thus the present method would be applicable toward a rapid and simple detection of Salmonella in food.
To investigate the practical usefulness of a newly developed agent, named the KMT reagent (Kida et al., 2004), a comparative study on sporicidal activities of the KMT reagent, peracetic acid (Acecide ®), chlorine dioxide (Exspor®), hydrogen peroxide, and sodium hypochlorite against Bacillus subtilis spores prepared at 22 or 37°C was performed. The spores prepared at 37°C were more resistant than those prepared at 22°C against the agents tested, and the sporulation temperature seemed to be an important factor in the determination of sporicidal activity. Acecide ® showed the most potent sporicidal activity among the agents tested. Exspor® also showed potent activity, but its activity, like that of sodium hypochlorite, was strongly inhibited by serum as an organic substance. The sporicidal activity of the KMT reagent was not as great as that of Acecide R, but it showed almost the same activity as 15% hydrogen peroxide. The KMT reagent possesses advantages in practical use over Acecide®and Exspor ®. We think the KMT reagent might be widely applicable as a universal sporicidal agent.