BS EN ISO 9308-1 pdf free download

BS EN ISO 9308-1 pdf free download. Water quality – Detection and enumeration of Escherichia coli and coliform bacteria – Part 1: Membrane filtration method.
3 Terms and definitions For the purposes of this part of ISO 9308, the terms and definitions given in ISO/IEC Guide 2 and the following apply. 3.1 lactose-positive bacteria ?Standard Test? bacteria capable of forming colonies aerobically at (36 ? 3) °C on a selective and differential lactose culture medium with the production of acid within (21 ? 3) h 3.2 coliform bacteria ?Standard Test? lactose-positive bacteria as defined in 3.1 which are oxidase-negative 3.3 Escherichia coli ?Standard Test? coliform bacteria as defined in 3.2 which also produce indole from tryptophan at (44,0 ? 0,5) °C within (21 ? 3) h 3.4 Escherichia coli ?Rapid Test? bile-resistant bacteria which also produce indole from tryptophan at (44,0 ? 0,5) °C within (21 ? 3) h 4 Principle 4.1 General description of the method The method is based on membrane filtration and consists of two parts, the reference Standard Test and the optional Rapid Test, which can be performed in parallel as described below. The Standard Test includes incubation of the membrane on a selective medium with subsequent further biochemical characterization of the typical lactose- positive colonies, leading to the detection and enumeration of coliform bacteria and E. coli within 2 d to 3 d. The Rapid Test consists of two incubation steps allowing the detection and enumeration of E. coli within (21 ? 3) h. If both tests, Standard Test and Rapid Test, are performed in parallel, the final result for E. coli shall be the higher of the two. 4.2 Filtration and incubation Test portions of the sample are filtered through membranes which retain the bacteria. One membrane (Standard Test) is placed on a selective lactose agar medium which is incubated at (36 ? 2) °C for (21 ? 3) h and one membrane (Rapid Test) on a casein (tryptic digest)-containing agar medium incubated at (36 ? 2) °C for 4 h to 5 h, followed by incubation at (44,0 ? 0,5) °C for 1 9 h to 20 h on an agar medium containing casein (tryptic digest) and bilesalts. 4.3 Evaluation and confirmation, Standard Test The characteristic colonies on the membrane are counted as lactose-positive bacteria. For coliform bacteria and E. coli, subculture is carried out of randomly selected characteristic colonies for confirmatory tests: oxidase and indole production. The numbers of lactose-positive coliform bacteria and E. coli likely to be present in 1 00 ml of the sample are counted. 4.4 Evaluation and confirmation, Rapid Test The colonies on the membrane which are able to form indole from the tryptophan supplied in the agar medium are counted as E. coli. The numbers of E. colilikely to be present in 1 00 ml of the sample are counted. 5 Apparatus and glassware Usual microbiological laboratory equipment, and in particular: 5.1 Apparatus for sterilization by steam (autoclave). Apparatus and glassware not supplied sterile shall be sterilized according to the instructions given in ISO 81 99. 5.2 Water bath and/or incubator, thermostatically controlled at (36 ? 2) °C. 5.3 Water bath and/or incubator, thermostatically controlled at (44,0 ? 0,5) °C. NOTE For the Rapid Test, instead of the incubators 5.2 and 5.3 a programmable incubator with dual setting may be used, set to (36 ? 2) °C and (44,0 ? 0,5) °C. 5.4 pH meter, with an accuracy of ? 0,1 . 5.5 Equipment for membrane filtration, in accordance with ISO 81 99.BS EN ISO 9308-1 pdf download.