バイオフィルム構成菌に関する基礎的研究

今回の検討により，冷却塔に発生したバイオフィルムでは，富栄養培地で比較的短時間に集落を形成できる菌種も構成菌種の一員であることが初めて明らかになった。しかし，これら分離株のバイオフィルム形成とその維持における役割や他の菌株との相互作用などはまったく未知の状態である。今後，こうしたことが明らかになればバイオフィルム形成抑制においても得策が見つかるかもしれない。We measured the number of bacteria in biofilms occurring in cooling towers in Tokyo with respect to nutrients in medium and days of culture, and observed rapidly growing bacterial species forming colonies after 2 days even in media with a high nutrient value such as BHI agar medium. Based on the partial base sequence of 16S rDNA, the bacterial species were identified as P.mosselii, P.alkaligenes, and P.alcaliphila. The absorbance of staining solution after staining of these isolates ranged from 0.44 for Microbacterium sp. to 10.10 for Sphingomonas acromaticivorans/subterranea, showing biofilm formation of all isolates. Biofilm formation differed among bacterial strains. However, biofilm formation was slightly higher in strains isolated in 1/100 medium

病院内水道水における貧栄養細菌の生息状況

To investigate the distribution of oligotrophic bacteria inhabiting hospital tap water, tap water samples were subjected to pour culture at 25℃ for 7 days using R2A agar medium. Bacteria were detected in 222 of 271 samples (81.9 %) collected nationwide, mainly in the Kanto district, revealing that oligotrophic bacteria are present at a very high frequency in hospital tap water. The distribution was investigated in relation to the geography or hospital management form, but no marked tendency was noted. The number of isolated oligotrophic bacteria varied from 1.0 × 10^0 CFU/ml to 2.8 × 10^4 CFU/ml among the samples, but the number was less than 1.0 × 10^1 CFU/ml in 54 samples accounting for the highest ratio (24.3 %). Of 538 oligotrophic isolates, 457 isolates (84.9 %) were gram-negative rods, and 108 isolates (23.6 %) were Methylobacterium, ranked the highest, followed by 71 isolates of Pseudomonas (15.5 %). However, identification of 274 isolates (60.0 %) was not possible. Gram-positive rods, Bacillus and Corynebacterium, and cocci, Micrococcus and Staphylococcus, were also isolated, although the frequencies were low. Based on these findings, the presence of oligotrophic bacteria which may cause opportunistic infections in tap water should be noted, when patients use tap water in hospitals, being susceptible to the infection

糞便汚染指標としての大腸菌検出に関する基礎的検討

各種特定酵素基質培地を用いて環境水から大腸菌の検出を試み,検出精度を中心に比較検討を行った。陽性管数の比較では,4種類の市販培地問に有意差は認められず,いずれの培地でも大腸菌検出に支障はなかった。偽陽性に関しては,C.koseri, E.hermannii, Y.regensburgei, Yersina sp., Aeromonas sp.などの菌種によっても陽性反応が起こることが明らかとなった。また,偽陰性に関しては,大腸菌のなかにもわずかながらβ-グルクロニダーゼ陰性株が存在することが確認された。このように,偽陽性および偽陰性の可能性は否定できないが,水道の分野では安全側に傾斜した評価のため,偽陽性は必ずしも試験法における大きな問題点とはならず,試験法の特性として,こうした事実を十分に認識した上で検査を行うことが重要である。A new water quality regulation came into effect in April 2004, and the microbiological test item of tap water, coliform group, has been changed to Escherichia coli. To investigate the accuracy of the new test method, we evaluated E.coli in environmental water using commercial culture media, and investigated false negativity and positivity. Four types of commercial medium were simultaneously used to detect E.coli. No significant difference was noted in the number of positive tubes, and E.coli was detectable using all media to a similar degree. Regarding false positivity, Citrobacter koseri, Escherichia hermannii, Yokenella regensburgei, Yersinia sp., and Aeromonas sp. showed positive reactions at a level of about 10^0-10^2 CFU. As for false negativity, 2 strains of E.coli were MUG reaction-negative. Therefore, false positivity and negativity may be judged, although the possibility is low

市販果汁飲料からの耐熱性好酸性菌の検出

To investigate contamination of commercial fruit juice beverages with thermostable acidophilic bacteria in Japan, 208 samples of fruit juice beverages produced in Japan and 162 samples of import beverages (total of 370 samples) purchased in 2005 were investigated according to the `Standard Test Method for Thermostable Acidophilic Bacteria\u27 proposed by the Japan Fruit Beverage Association. TAB was isolated from 9 of the beverages made in Japan (4.3%) and 19 of the import beverages (11.7%), showing about a 3-fold higher isolation rate. The origins of the import beverages from which TAB was isolated were widely distributed : Thailand, Indonesia, Korea, France, Germany, Spain, Australia, America, Mexico, and South Africa. Three of the 9 domestic products from which TAB was isolated were mix juice. As the 2nd most frequently contaminated beverage, 2 orange juice products were contaminated, and 1 sample each of apple, grape, grape fruit, and pineapple juices were also contaminated. Regarding the import beverages, 5 of the 19 samples from which TAB was isolated were mix juice, as in the Japan-made products. The 2nd most frequently contaminated beverages were 3 orange juice products. TAB was also isolated from 2 samples each of grape, mango, and pineapple juices, and 1 sample each of apple, cherry, peach, and prune juices. TAB was isolated from various fruit juice beverages regardless of whether they were domestic products or imports. All of the 9 Japan-made beverages contaminated with TAB were concentrated products, and the bacteria were not detected in any of the pure direct products. The same tendency was noted in the import beverages. Ten of the 19 samples (52.6%) contaminated with TAB were concentrated, and only 1 straight sample (5.3%) was contaminated. Seven of the 9 contaminated domestic products (77.8%) were paper-packed, and 1 sample each was packed in a can or PET bottle. As for the import beverages, 8 beverages (42.1%) were most frequently paper-packed, as in the Japan-made products, and 6 (31.6%), 3 (15.8%), and 2 (10.5%) beverages were packed in a bottle, PET bottle, and can, respectively