McDaniels A E, Bordner R H, Gartside P S, Haines J R, Brenner K P, Rankin C C
Appl Environ Microbiol. 1985 Oct;50(4):755-62. doi: 10.1128/aem.50.4.755-762.1985.
Standard procedures for analyzing drinking water stress the need to adhere to the time and temperature conditions recommended for holding samples collected for microbiological testing. The National Drinking Water Laboratory Certification Program requires compliance with these holding limits, but some investigators have reported difficulties in meeting them. Research was conducted by standard analytical methods to determine if changes occurred when samples were held at 5 and 22 degrees C and analyzed at 0, 24, 30, and 48 h. Samples were analyzed for coliforms by the membrane filter and fermentation-tube procedures and for heterotrophs by the pour plate method. A total of 17 treated water samples were collected from a large municipal distribution system from August to December 1981, and 12 samples were collected from January to May 1983. The samples were dosed with coliforms previously isolated from the water system, Enterobacter cloacae in 1981 and Citrobacter freundii in 1983. The coliform counts declined linearly over time, and the rates of decline were significant at both 5 and 22 degrees C. Within 24 h at 22 degrees C, levels of E. cloacae and C. freundii decreased by 47 and 26%, respectively, and at 5 degrees C, E. cloacae numbers declined by 23%. Results from these representative laboratory-grown coliforms reinforced those previously obtained with naturally occurring coliforms under the same experimental conditions. Significantly, some samples with initially unacceptable counts (greater than 4/100 ml) met the safe drinking water limits after storage at 24 h at 5 and 22 degrees C and would have been classified as satisfactory.(ABSTRACT TRUNCATED AT 250 WORDS)
分析饮用水的标准程序强调，对于为微生物检测而采集的样本，必须严格遵守所推荐的保存时间和温度条件。国家饮用水实验室认证计划要求符合这些保存期限规定，但一些调查人员报告称难以做到。本研究采用标准分析方法，以确定样本在5摄氏度和22摄氏度下保存，并在0小时、24小时、30小时和48小时进行分析时是否会发生变化。通过膜过滤法和发酵管法分析样本中的大肠菌群，通过倾注平板法分析样本中的异养菌。1981年8月至12月，从一个大型市政供水系统中总共采集了17份经处理的水样，1983年1月至5月采集了12份水样。这些样本接种了先前从该供水系统中分离出的大肠菌群，1981年接种阴沟肠杆菌，1983年接种弗氏柠檬酸杆菌。大肠菌群数量随时间呈线性下降，在5摄氏度和22摄氏度下下降速率均显著。在22摄氏度下24小时内，阴沟肠杆菌和弗氏柠檬酸杆菌的数量分别下降了47%和26%，在5摄氏度下，阴沟肠杆菌数量下降了23%。这些具有代表性的实验室培养大肠菌群的结果，强化了先前在相同实验条件下对天然存在的大肠菌群所获得的结果。值得注意的是，一些初始计数不可接受（大于4/每百毫升）的样本，在5摄氏度和22摄氏度下保存24小时后符合安全饮用水限量标准，原本会被判定为合格。（摘要截选至250字）
