Rapid, High-Throughput Identification of Contaminated Drinking Water
New method allows rapid ATP quantification to identify bacterial contamination in water supplies
November 25, 2021
Safe and readily available water is perhaps one of the most fundamental requirements in any society. According to the World Health Organization (WHO)(1), access to clean water is a leading factor in raising a country’s economic growth and contributes greatly to a reduction in poverty. Even in first-world countries where most people don’t give a second thought to their water or where it comes from, outbreaks of disease spread through municipal water supplies are far from being uncommon. According to the Centers for Disease Control (CDC)(2), the five leading causes of outbreaks in the United States are, in order of prevalence: Giardia, Legionella, Norovirus, Shigella, and Campylobacter, with other diseases including Salmonella, E.coli, Cryptosporidium, and Hepatitis A also putting in an appearance.
Since we cannot reliably predict where bacteria might enter our municipal water supplies, rapid water testing becomes the front-line tool in preventing outbreaks. Current detection methods largely rely on cell culture and microscopy techniques. However, these methods are slow, time-consuming, and can produce inaccurate results for some types of bacteria, which can lead to a delayed response and allow pathogens to spread further through a population before action is taken.
An alternative testing method already in use by the research, food, and healthcare industries relies on the detection of microbial cellular adenosine triphosphate (ATP). As ATP is produced by all bacteria it enables detection of the presence of bacteria without needing to specify a priori which bacteria we want to test for. Once a positive ATP test has been confirmed, additional targeted water testing can be used to determine the species and source of the contamination. However, the method is generally used on a single sample basis and is thus not useful as a front-line method for high-throughput sample testing..
A rapid high-throughput method for ATP quantification in drinking water
Scientists at Dalhousie University in Halifax, Nova Scotia have been working to devise rapid, high-throughput drinking water testing protocols without sacrificing accuracy. In a 2020 publication(3) they describe a modified ATP analysis method that can be used as a rapid, simple, and high-throughput water quality screen to identify bacterial contamination in drinking water.
ATP assays traditionally use luciferase as a reporter enzyme; the amount of light emitted when luciferin and ATP react is directly proportional to the amount of ATP in the sample. The researchers wanted to incorporate this reporting mechanism into their new assay, while at the same time developing a high-throughput format suitable for front-line screening.
The team chose to use a Pall multi-well vacuum manifold paired with AcroPrep™ Advance 96-well filter plates for their sample filtration, a crucial step in the preparation of samples for analysis. AcroPrep Advance 96-well filter plates are designed to meet quality guidelines set forth by the Society of Biomolecular Screening (ANSI/SBS x-2004) for multi-well plates. The plates incorporate design features that increase well-to-well consistency for sample recovery and reduce the chance of cross-contamination following filtration.
The researchers split their process development into two main phases: Phase 1, validating data acquisition and readout, and phase 2, validating sample filtration and ATP extraction. The team needed to be sure that the new assay was as least as accurate and sensitive as traditional, low-throughput methods. To meet their criteria for success they would also need to show a significant increase in sample processing speed.
The team used a set of known contaminated water samples for analysis, with purified water as a negative control. Statistical analysis confirmed that the microplate reader the research team used could detect ATP at concentrations typically observed in contaminated drinking water. The team also demonstrated equivalent detection and quantification of ATP concentrations across different samples when using the new high-throughput and the existing low-throughput methods.
Sample concentration and ATP extraction capabilities of the vacuum manifold and AcroPrep filter plate set up were then compared to manual syringe filter methods also currently in use. No significant differences were found between the two methodologies for filtration of environmental water samples and the detection of contamination.
Finally, the research team tested the speed and throughput differences between the manual and new high-throughput methods for water testing. Using the high-throughput method, the team was able to test an average of one sample per minute, a five-fold gain in efficiency over manual sampling methods. Furthermore, the new method uses automated data acquisition and readout, leaving the operator free to perform other tasks while data analysis was being performed.
The newly developed method can be used by water testing facilities to measure microbial biomass in environmental water samples five times faster than current front-line methods. This has the potential to significantly improve water contamination detection and speed public health responses.
Learn more about the AcroPrep Advance 96-well filter plates used in this protocol, as well as other products designed to streamline sample preparation across a wide variety of applications.
1. World Health Organization. 2019. Drinking-Water Fact Sheet. [Online] Available at: https://www.who.int/news-room/fact-sheets/detail/drinking-water [Accessed 20 October 2021]
2. Centers for Disease Control and Prevention. 2014. Water-related Diseases and Contaminants in Public Water Systems. [Online] Available at: https://www.cdc.gov/healthywater/drinking/public/water_diseases.html [Accessed 20 October 2021]
3. Secka F, et al. (2020) An automated and high throughput method for adenosine triphosphate quantification. AWWA Wat Sci. e1202. https://doi.org/10.1002/aws2.1202