5a-h, a series of (5-substituted-2-methyl-1,3-thiazole-4-yl) acetic acids as heterocyclic acetic acid derivatives, was designed and synthesized from ethyl acetoacetate. The synthesized compounds were screened for their antimicrobial activities against bacterial and fungal strains, and their characteristics were investigated by assays under various temperature and pH conditions. Cytotoxicity was evaluated with the use of sheep erythrocytes and human neonate dermal fibroblasts. Similarly, agents such as lauric acid 6 and parabens 7a-b, which are used as preservative agents for commercial cosmetics and detergents, were assayed for comparison. Although the structure of 5a is simple, comprising a thiazole attached with an octyl group and acetic acid moiety, the compound showed stronger and broader antibacterial and antifungal activities among the 5 series against the tested microbes other than gram-negative bacteria. Interestingly, 5a overcame the weak antifungal activity of parabens 7a-b. Also, the cytotoxicity of 5a was less than that of parabens 7a-b, especially to human dermal fibroblasts. These results suggest that thiazolyl-acetic acid 5a is a potentially effective biocide, and that it could be used as a preservative agent in commercially sold cosmetics and detergents, facilitated by the hydrophilic and charge properties of its carboxylic acid moiety.
Bacteria tests are conducted for quality control in many different industries. However, the cultivation method takes a long period of time to obtain results and there are more than a few bacteria that are difficult to cultivate. We have focused on the autofluorescence substance in the bacteria to detect them, and developed a sensor to measure the bacteria in real-time, without any pretreatments or addition of any reagents. This system uses a 405nm laser focused on the sample flowing through the flow-cell in order to detect the fluorescent light from the bacteria as well as scattered light. Fluorescent light and scattered light are separated by a dichroic mirror, and the number of viable particles (bacteria) and that of non-viable particles are obtained. We tested this system using fluorescent polystyrene latex particles and several bacterial strains, and confirmed that it had good detection capability. We believe that this system will become a next-generation bacteria detection system and help the introduction of PAT (process analytical technology) to all areas where real time and on-site detection is needed.
The oxidative power of hydroxyl radicals has been applied to disinfection systems for the purpose of oral hygiene by utilizing blue light-induced photolysis of hydrogen peroxide (H2O2) in our laboratory. In the present study, the bactericidal potential of blue light-irradiated oxydol products via hydroxyl radical generation was compared with that of 3% (w/v) H2O2. Eleven commercially available oxydol products were used in the present study. Even though a few of the products that contained ethanol, a hydroxyl radical scavenger, as an additive showed slightly lower hydroxyl radical yield as compared with 3% (w/v) H2O2, the blue-light irradiation of each oxydol product for 3 min showed similar or superior bactericidal activity against Staphylococcus aureus to that of 3% (w/v) H2O2. The results strongly suggest that any of the oxydol products tested in the present study can be used as a source of hydroxyl radicals for the disinfection technique developed in our laboratory.
Growth prediction of a four-strain cocktail of Salmonella Enteritidis in commercial products of pasteurized and unpasteurized liquid whole egg was studied with the new logistic model that we developed. The growth data of the pathogen in the liquid egg products at constant temperatures in our recent study (Sakha and Fujikawa, Biocont. Sci., 2012) were used for prediction. With estimated values of the parameters in the model, it successfully predicted the Salmonella growth in the liquid egg products at dynamic temperature conditions in the high and low ranges. The Baranyi model, which is well known worldwide, could predict Salmonella growth in the pasteurized product at the dynamic temperature conditions in the high range only. This study would be, in our knowledge, the first report on the prediction of Salmonella growth in both pasteurized and unpasteurized liquid egg products at dynamic temperature conditions with a mathematical model.
Spoilage of fruit juices by a thermoacidophilic spore-forming bacterium, Alicyclobacillus acidoterrestris, is a big problem for fruit juice industries worldwide. We have developed a novel chromogenic selective agar medium (EAATSM) for the isolation and enumeration of A. acidoterrestris. A. acidoterrestris strains appeared as blue colonies on the EAATSM. Other Alicyclobacillus strains appeared as white colonies or were inhibited. A study comparing EAATSM and YSG agar was carried out using artificially contaminated samples of 50 fruit juice products. The correlation coefficient between EAATSM and YSG was 0.991.
From the viewpoint of the quality assurance of laboratory animals, it is important to guarantee that they have not accidentally been exposed to any stress during breeding. In this study, we investigated non-invasive indicators of the exposure of mice to stress. The stress of horizontal shaking and no-bedding was applied to mice and the intestinal bacterial flora in their feces was analyzed. The cell density of total lactic acid bacteria was influenced by the shaking stress but not affected by the no-bedding stress. In contrast, the cell density of Lactobacillus, a member of lactic acid bacteria, decreased significantly to 1/10 at 48 h under both types of stress. Therefore, the cell density of Lactobacillus in feces may be used as a non-invasive bio-indicator of the stress exposure of mice.
In May 2012, strain HNN-6 (=JCM 18566) , a Gram-negative, non-spore-forming, motile and strictly aerobic rod, which produces a pale orange pigment, was isolated from a hot spring water sample obtained in Kagoshima, Japan, by a plating method using R2A medium at 30°C for 7 d. The 16S rRNA gene sequences (1,437bp) of this strain (accession number: AB731137) had a close similarity (99.1%) to Hydrotalea sandarakina AF-51T (JF739858) . Growth occurred at 25-45°C and pH 5.0-8.0, with optimal growth at 40°C and pH 6.0-7.0. Growth did not occur in the presence of ≧2% NaCl. The API 20NE identification system gave positive results for nitrate, aesculin, gelatin, 4-nitrophenyl-β-D-galactopyranoside, D-glucose, D-mannose, maltose and oxidase (API code number 1472204) . The dominant cellular fatty acids of strain HNN-6 were iso-C15:0 (32.6%) , iso-C17:0 3-OH (24.2%) and iso-C16:0 (8.4%) . The guanine-plus-cytosine (G+C) content of DNA was 36.2 mol%. This article is the first report to describe the characteristics of an orange-pigmented bacterium isolated from a hot spring water sample in Japan.
EHEC-chrom, a novel chromogenic screening agar medium for enterohemorrhagic Escherichia coli (EHEC) , was developed. A total of 52 EHEC strains, which were studied for the inclusivity study, grew and formed blue-green colored colonies on EHEC-chrom. When 43 gram-negative bacteria other than EHEC were inoculated for the exclusivity study, 10 strains grew and formed colorless colonies. A total of 28 gram-positive bacteria failed to grow and 1 yeast strain grew as colorless colonies. EHEC-chrom was compared with CHROMagarTM STEC, XM-EHEC agar and CT-MacConkey base agar with a specific sugar (CT-SorbitolMAC, CT-rhamnoseMAC and CT-sorboseMAC) as commercially available selective agar using 100 food samples artificially contaminated with low levels (<10 logCFU/25g) of EHEC. Numbers of samples from which EHEC was recovered by using EHEC-chrom, CHROMagarTM STEC, XM-EHEC agar and CT-MacConkey base agar with specific sugar were 62, 58, 59 and 60, respectively. Our results suggested EHEC-chrom was a useful alternative for EHEC screening in food.