On the track for an efficient detection of Escherichia coli in water: A review on PCR-based methods

Abstract

Ensuring water safety is an ongoing challenge to public health providers. Assessing the presence of fecal contamination indicators in water is essential to protect public health from diseases caused by waterborne pathogens. For this purpose, the bacteria Escherichia coli has been used as the most reliable indicator of fecal contamination in water. The methods currently in use for monitoring the microbiological safety of water are based on culturing the microorganisms. However, these methods are not the desirable solution to prevent outbreaks as they provide the results with a considerable delay, lacking on specificity and sensitivity. Moreover, viable but non-culturable microorganisms, which may be present as a result of environmental stress or water treatment processes, are not detected by culture-based methods and, thus, may result in false-negative assessments of E. coli in water samples. These limitations may place public health at significant risk, leading to substantial monetary losses in health care and, additionally, in costs related with a reduced productivity in the area affected by the outbreak, and in costs supported by the water quality control departments involved. Molecular methods, particularly polymerase chain reaction-based methods, have been studied as an alternative technology to overcome the current limitations, as they offer the possibility to reduce the assay time, to improve the detection sensitivity and specificity, and to identify multiple targets and pathogens, including new or emerging strains. The variety of techniques and applications available for PCR-based methods has increased considerably and the costs involved have been substantially reduced, which together have contributed to the potential standardization of these techniques. However, they still require further refinement in order to be standardized and applied to the variety of environmental waters and their specific characteristics. The PCR-based methods under development for monitoring the presence of E. coli in water are here discussed. Special emphasis is given to methodologies that avoid pre-enrichment during the water sample preparation process so that the assay time is reduced and the required legislated sensitivity is achieved. The advantages and limitations of these methods are also reviewed, contributing to a more comprehensive overview toward a more conscious research in identifying E. coli in water.

Plasmonic bacteria on a nanoporous mirror via hydrodynamic trapping for rapid identification of waterborne pathogens

“…Compared with selective culturing, molecular diagnosis exhibits better sensitivity and a faster detection time. However, this technique requires an additional sample preparation step to enrich the bacteria, which are dispersed in a large volume of water 7 . Moreover, this process still takes several hours and needs expensive reagents and equipment 8 , 9 .…”

Electrochemical Quantification of Escherichia coli with DNA Nanostructure

“…A Raman spectroscopic method, though rapid, is less sensitive with an LOD of 10 CFU mL −1 and less specific as well as requiring a sample processing step prior to the measurement . PCR‐based methods suffer from, among many others, membrane‐clogging and contamination from mixture components . Though separation of the bacteria from its solvent may be advantageous, it requires additional steps that lengthen the overall process time and more steps increase the chance of random errors introduction.…”

Recent Progress in Lectin-Based Biosensors

“…Conventional methods for bacteria detection, such as culture and colony counting [80] and enzyme-linked immunosorbent assay [81] are somewhat laborious and time-consuming. Consequently, alternative methods are required for the rapid and reliable detection of bacteria.…”