Feasibility of methods based on nucleic acid amplification techniques to fulfil the requirements for microbiological analysis of water quality.

Molecular methods based on nucleic acid recognition and amplification are valuable tools to complement and support water management decisions. At present, these decisions are mostly supported by the principle of end-point monitoring for indicators and a small number of selected measured by traditional methods. Nucleic acid methods show enormous potential for identifying isolates from conventional culture methods, providing data on cultivable and noncultivable micro-organisms, informing on the presence of pathogens in waters, determining the causes of waterborne outbreaks, and, in some cases, detecting emerging pathogens. However, some features of water microbiology affect the performance of nucleic acid-based molecular techniques and thus challenge their suitability for routine water quality control. These features include the variable composition of target water samples, the generally low numbers of target micro-organisms, the variable water quality required for different uses and the physiological status or condition of such micro-organisms. The standardization of these molecular techniques is also an important challenge for its routine use in terms of accuracy (trueness and precision) and robustness (reproducibility and reliability during normal usage). Most of national and international water regulations recommend the application of standard methods, and any new technique must be validated respect to established methods and procedures. Moreover, molecular methods show a high cost-effectiveness value that limits its practicability on some microbial water analyses. However, new molecular techniques could contribute with new information or at least to supplement the limitation of traditional culture-based methods. Undoubtedly, challenges for these nucleic acid-based methods need to be identified and solved to improve their feasibility for routine microbial water monitoring.