We examined antibacterial cutting boards with antibacterial activity values of either “ 2 ” or “ 4 ” in compliance with the JIS Z 2801 standard, and compared their findings with those of cutting boards with no antibacterial activity. These cutting boards were used in ten different households, and we measured changes in the viable cell counts of several types of bacteria with the drop plate method. We also identified the detected bacterial flora and measured the minimum antimicrobial concentrations of several commonly used antibacterial agents against the kinds of bacteria identified to determine the expected antibacterial activity of the respective agents. Cutting boards with activity values of both “ 2 ” and “ 4 ” proved to be antibacterial in actual use, although no correlation between the viable cell counts and the antibacterial activity values was observed. In the kitchen environment, large quantities of Pseudomonas, Flavobacterium, Micrococcus, and Bacillus were detected, and it was confirmed that common antibacterial agents used in many antibacterial products are effective against these bacterial species. In addition, we measured the minimum antimicrobial concentrations of the agents against lactobacillus, a typical good bacterium, and discovered that this bacterium is less sensitive to these antibacterial agents compared to more common bacteria.
The plasma of several different gases has shown a sporicidal activity. From these gases, nitrogen gas was most difficult to produce atomic nitrogen radicals. However, these radicals have a high energy, indicating that nitrogen gas plasma could be used to sterilize microorganisms and inactivate endotoxins. The sterilization mechanism of nitrogen gas plasma is the synergistic effect of a high rising-up voltage pulse, UV irradiation and atomic nitrogen radicals. Thus, the target cells were damaged by degradation, which resulted in death. The biological indicator (BI) used in this study was Geobacillus stearothermophilus ATCC 7953 at a population of 1×106 CFU/sheet. Sterility assurance was confirmed by using the Bl. Moreover, endotoxins were successfully inactivated. More than 5 log reduction of endotoxins could be attained with 30 minutes of nitrogen gas plasma exposure. Material functionality influenced by nitrogen gas plasma presented a satisfactory result. No deterioration of polymers could be observed by nitrogen gas plasma exposure.
This study compared the antifungal activities of bronopol and 2-methyl-4-isothiazolin-3-one (MT) against members of the genus Saprolegnia in the family saprolegniaceae, which have the ability to infect fish. The minimum inhibitory concentration of bronopol was 100-200 mg/I but for MT it was 31 mg/I. Concerning fungicidal effects against the hyphae, treatment with bronopol at 100-200 mg/I for 30 min or treatment with MT at 25-50 mg/I for 30 min was effective in killing the vegetative stage of all fungal strains tested. Treatment with bronopol at 100 mg/I for 60 min or treatment with MT at 25-50 mg/I for 60 min was effective in killing the zoospores of all fungal strains tested. These results showed that MT was a more effective antifungal agent than bronopol against infectious members of the genus Saprolegnia.
This study was conducted to investigate the susceptibility of the biofilm cells of Escherichla coil O 157, Salmonella Enteritidis, and Staphylococcus aureus to some cleaning detergents and sanitizers. No weakly acidic, neutral, and weakly alkaline detergent could remove the biofilm bacteria from stainless steel chips at commonly used concentrations recommended by manufacturers. Among sanitizers, sodium hypochlorite did not completely inactivate any biofilm bacteria at active chlorine concentrations of 25 to 200μg/ml. Benzalkonium chloride, alkyldiaminoethyl glycine hydrochloride, chlorhexidine digluconate, and polyhexamethylenebiganide inactivated the great majority of E. coil and S. Enteritidis at commonly used concentrations, but did not inactivate S. aureus effectively enough. The biofilm S. aureus population was shown to be more tolerant than the E. coil and S. Enteritidis populations to the sanitizers.
Duopath Legionella (Merck KGaA, Darmstadt, Germany) is a rapid and simple immunochromatographic assay kit for the identification of Legionella species. We evaluated the precision of the kit in identifying 100 strains of Legionella and 35 strains of non-Legionella bacteria isolated from cooling tower and bath water samples. Consequently, of all the Legionella strains tested, 99 strains were judged to be Legionella, and only one strain (Legionella busanensis) was judged to be non-Legionella. All of the 35 non-Legionella strains were judged to be non-Legionella. We therefore conclude that Duopath Legionella is a useful method for the rapid identification of Legionella.