Havelaar A H, Hogeboom W M, Sekhuis V M, van Erne E H
J Appl Bacteriol. 1987 Jun;62(6):555-64. doi: 10.1111/j.1365-2672.1987.tb02689.x.
In a 3-year period, four series of simulated water samples containing selected test strains were distributed to more than 50 laboratories in The Netherlands for bacteriological testing. Participating laboratories examined the samples by enrichment or membrane filtration methods, or both, for total coliform organisms, thermotolerant coliform organisms, faecal streptococci and standard plate counts (37 degrees and 22 degrees C) according to Dutch standard methods. The results were quantitatively satisfactory: the distribution of positive and negative results with subsamples conformed to stochastic variation; the standard deviation of membrane or plate counts was usually in the range which may be expected from a Poisson distribution, and there was good correspondence between average counts in participating laboratories and those expected from controls in the organizing laboratory. Problems of a qualitative nature were frequently encountered, however. Among them were a false positive response with a strain of Enterobacter cloacae in the thermotolerant coliform test; a false positive result with Clostridium perfringens in enrichment tests for total or thermotolerant coliform organisms and false positive results with Micrococcus varians in the faecal streptococcus test by membrane filtration. It is concluded that quality assessment should be a consistent activity in water microbiology laboratories. For this purpose, stable and well characterized reference materials are needed.
在三年时间里，四组含有选定测试菌株的模拟水样被分发给荷兰50多个实验室进行细菌学检测。参与的实验室根据荷兰标准方法，通过富集或膜过滤方法，或两种方法同时使用，检测样品中的总大肠菌群、耐热大肠菌群、粪链球菌和标准平板计数（37摄氏度和22摄氏度）。结果在数量上令人满意：子样本的阳性和阴性结果分布符合随机变化；膜计数或平板计数的标准差通常在泊松分布预期的范围内，参与实验室的平均计数与组织实验室对照预期的计数之间有良好的对应关系。然而，经常遇到定性性质的问题。其中包括在耐热大肠菌群检测中阴沟肠杆菌菌株出现假阳性反应；在总大肠菌群或耐热大肠菌群的富集检测中，产气荚膜梭菌出现假阳性结果，以及在膜过滤法进行的粪链球菌检测中，变异微球菌出现假阳性结果。得出的结论是，质量评估应该是水微生物学实验室的一项持续活动。为此，需要稳定且特征明确的参考材料。
