Water Journal : Water Journal December 2011
microbiology refereed paper technical features 84 DECEMBER 2011 water perusal of existing data potentially provides information about the likely levels and prevalence of the target micro- organisms in the water type of interest, thereby simplifying decision making about the monitoring program and/or obviating the need for a pilot monitoring program to establish these parameters. Prior information about the likely prevalence and levels of micro-organisms in a water source assists in determining the method detection limits and the total number of samples that are required for meaningful data to be obtained. A search for relevant data not only assists in the planning and design of monitoring programs and in improving the quality of documentation of program results (see Step 8), but also gives an awareness of data gaps and focuses attention on research and method development(s) that are required. Step 3: Laboratory Attributes and Accreditation Of primary importance to assure the quality of generated data is that the testing laboratory engaged to conduct microbiological testing is one that is technically competent. In Australia, the National Association of Testing Authorities, Australia (NATA) undertakes laboratory accreditations for technical competence. The criteria for determining a facility's competence are based on the relevant international standard (for water-testing laboratories this is ISO/IEC 17025) and include: the qualifications, training and experience of staff; correct equipment that is properly calibrated and maintained; adequate quality assurance procedures and appropriate sampling practices. In addition, ISO/IEC 17025 requires testing laboratories to have and apply procedures to estimate the uncertainty of their measurements and to communicate such estimates to their customers (ISO/IEC, 2005). Additionally, accredited laboratories are required to participate in inter- laboratory proficiency programs for relevant micro-organisms, where available, to support their other quality control activities. While laboratories must meet a minimum standard to become accredited this does not mean that all accredited laboratories are at the same standard. Accordingly, it is important to base the selection of the testing laboratory upon additional criteria as follows: • The laboratory's scope of accreditation (does the laboratory's scope of accreditation include the micro- organism(s) of interest?) • In the event that a laboratory offers a test that is not a standard method, does the laboratory have supporting validation or verification data available for perusal? • Has the laboratory estimated the measurement uncertainty (MU) associated with the test result for the method of interest and is this estimate available? • Can the laboratory provide information about the method such as recovery efficiency, method sensitivity, performance of the method using different matrices (e.g. low- versus high-turbidity waters) as well as, or as a substitute for, MU estimates? In commissioning a testing laboratory it is important that questions are asked about the availability of MU estimates for methods of interest, and this is particularly important where results are being compared to a regulatory standard or specification limit. With knowledge of MU, appropriate management strategies can be designed which take into proper account the potential risk associated with decisions based on test results. Step 4: Liaison with Laboratory Personnel In communicating with the testing laboratory when designing a water quality program, it is important that personnel with whom discussion is engaged are not only familiar with the detail of available methods but that they are also familiar with the latest methodological advances and alternative approaches that may be used to meet program objectives. This may, but not necessarily, require direct contact with personnel responsible for sample analysis. Step 5: What Micro-organism Should Be Selected? The selection of the micro-organism for testing, while dictated by the research question/objective of the water quality monitoring program, also depends on the availability of a suitable analytical method. For example, the study objective may be to monitor the level of viruses in sewage, yet currently there are no suitable cell-culture methods for rotaviruses and noroviruses, which have the highest pathogenicity and are likely to be present in high numbers in human waste. Accordingly, investigation of viral risk may require that a decision be made to: i) test for other pathogenic viruses for which cell-culture methods are available; ii) test for the target viruses using polymerase chain reaction (PCR) methods which detect both viable and non-viable viruses Step 3: Summary • Is the laboratory NATA accredited and does the laboratory's scope of accreditation include those methods and/or micro-organisms of interest? • Can the laboratory provide Measurement Uncertainty (MU) data and/or data about the performance characteristics of the method(s)? Step 4: Summary Is the person with whom discussions are engaged familiar with: • Details of available methods? • Validation and verification data that supports the use of non-standard or modified methods offered by the laboratory? • Quality assurance data held (method sensitivity, recovery efficiency, detection limits)? • Latest 'research' methods? • Expected levels and prevalence of pathogens in different water types? Step 5: Summary • Is there any scope in the selection of micro-organism to meet monitoring objectives? • What choices of micro-organism are offered by the laboratory? Do the methods offered fall under the scope of (technical) accreditation of the laboratory? • Are there any standard methods for micro-organism in question? • Can the laboratory provide data to support the use of microbial and/or other surrogates? • Can the laboratory provide data about the relationship between viable and total numbers of the target micro-organism?
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