Evaluation of the Anderson Baird-Parker direct plating method for enumerating Escherichia coli in water.
The direct plating (DP) method for enumerating Escherichia coli in food was adapted for water analysis by membrane filtration and a standardized protocol was described. The DP method was found to give equal or better recoveries of E. coli than a membrane filtration method using 0.1% sodium lauryl sulphate agar; the repeatability of the DP method was markedly better. The necessity to transfer membranes from the non-selective medium tryptone soy agar (TSA) to the selective medium tryptone bile agar (TBA) after pre-incubation for 4 h was considered disadvantageous for practical purposes. A double-layer method, where the membrane filter is placed on a layer of TSA poured over TBA, with incubation in an incubator that automatically switches from 37 degrees to 44 degrees C after 4 h, was found to be an acceptable alternative. Recovery of E. coli and inhibition of competitive flora were equal or only slightly less than for the standard DP method.
Havelaar
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Laboratory of Water and Food Microbiology, National Institute of Public Health and Environmental Hygiene, Bilthoven, The Netherlands.
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D001431:Bacteriological Techniques; D003470:Culture Media; D004926:Escherichia coli / Q000254:growth & development* / Q000302:isolation & purification; D013696:Temperature; D014871:Water Microbiology; D014876:Water Pollution
D003470:Culture Media