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Comparison of methods for determining the numbers and species distribution of coliform bacteria in well water samples
Author(s) -
Niemi R.M.,
Heikkilä M.P.,
Lahti K.,
Kalso S.,
Niemelä S.I.
Publication year - 2001
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1046/j.1365-2672.2001.01314.x
Subject(s) - coliform bacteria , bacteria , indicator organism , biology , distribution (mathematics) , microbiology and biotechnology , environmental science , mathematics , genetics , mathematical analysis
R.M. NIEMI, M.P. HEIKKILÄ, K. LAHTI, S. KALSO AND S.I. NIEMELÄ. 2001. Aims: Enumeration of coliform bacteria and Escherichia coli is the most widely used method in the estimation of hygienic quality of drinking water. The yield of target bacteria and the species composition of different populations of coliform bacteria may depend on the method. Three methods were compared. Methods and Results: Three membrane filtration methods were used for the enumeration of coliform bacteria in shallow well waters. The yield of confirmed coliform bacteria was highest on Differential Coliform agar, followed by LES Endo agar. Differential Coliform agar had the highest proportion of typical colonies, of which 74% were confirmed as belonging to the Enterobacteriaceae. Of the typical colonies on Lactose Tergitol 7 TTC agar, 75% were confirmed as Enterobacteriaceae, whereas 92% of typical colonies on LES Endo agar belonged to the Enterobacteriaceae. LES Endo agar yielded many Serratia strains, Lactose Tergitol 7 TTC agar yielded numerous strains of Rahnella aquatilis and Enterobacter , whereas Differential Coliform agar yielded the widest range of species. Conclusions: The yield of coliform bacteria varied between methods. Each method compared had a characteristic species distribution of target bacteria and a typical level of interference of non‐target bacteria. Identification with routine physiological tests to distinct species was hampered by the slight differences between species. High yield and sufficient selectivity are difficult to achieve simultaneously, especially if the target group is diverse. Significance and Impact of the Study: The results showed that several aspects of method performance should be considered, and that the target group must be distinctly defined to enable method comparisons.