Detection Of Pathogens In Water Research Articles

Detection of pathogens in water using long range surface plasmon resonance biosensor: Numerical investigation

This work presents a numerical demonstration for improving the imaging sensitivity of long-range surface plasmon (LRSPR) biosensors using the prism 2S2G/cytop/Cu/Gr (Graphene)/sensing medium (SM) configuration. In the suggested LRSPR biosensor, the imaging sensitivity is compared to that of the traditional surface plasmon sensor (tSPR) through numerical analysis. The proposed LRSPR sensor reaches 4655.7/RIU as its maximum imaging sensitivity for detecting E. coli bacteria. The maximum electric field intensity is found at the interface between the Cu/SM in the tSPR sensor and the Gr/SM in the proposed sensor. For pathogens detection such as pure-water (P.W.), Vibrio-Cholera (V.C.), Escherichia-Coli (E.coli), Bacillus-Anthracis (B.A.), and Enterococcus -aecalis (B.F), the penetration depth (PD) for the LRSPR sensor are 304.46 nm, 955.45 nm, 961.45 nm, 957.44 nm and 1050.7 nm. The LRSPR sensor's effectiveness in biosensing applications is further demonstrated by its figure of merit (FoM) for the detection of pathogens bacteria, which is 291.8/RIU (V.C), 781.5/RIU (E.coli), 59.28/RIU(B.A.) and 738.5/RIU (E.F.), respectively.

QCM Biosensors for pathogen detection in water and food: review of published literature

Introduction:This article is the result of the review “QCM Biosensors for the Detection of Pathogens in Water and Food: A Review,’ conducted during the years 2023 and 2024 at the Universidad Distrital Francisco José de Caldas”Problem: The fast evolution of pathogen detection through biosensors requires a continuous synthesis of literatu-re to provide an integral comprehension of the state of the art to new researchers. Objective:Perform bibliography research about QCM Biosensors used for pathogen detection in food and water covering a period from 2018 to 2023.Methodology: The research includes three phases: An explanation of the principles of QCM biosensors, their use in water and food pathogen detection, and their use in industry, with an emphasis on water quality.Result:QCM biosensors are solid, measure mass changes at the micro and nanometric scales, and are widely used in the food industry due to their accuracy and ease of use.Conclusion: The review highlights the effectiveness of QCM biosensors when detecting different food contami-nants and pathogens. It underlines the practical research necessity and importance of updating review papers to orientate future investigations in this specific area.Originality:The originality of this review lies on its detailed approach to QCM biosensor use in food pathogen detection.Limitations:The constant evolution of the field of pathogen detection in addition to the diversity of QCM biosen-sors and the wide range of pathogens studied may make it difficult to generalize certain findings.

Development of an Immunocapture-Based Polymeric Optical Fiber Sensor for Bacterial Detection in Water.

Conventional methods for pathogen detection in water rely on time-consuming enrichment steps followed by biochemical identification strategies, which require assay times ranging from 24 hours to a week. However, in recent years, significant efforts have been made to develop biosensing technologies enabling rapid and close-to-real-time detection of waterborne pathogens. In previous studies, we developed a plastic optical fiber (POF) immunosensor using an optoelectronic configuration consisting of a U-Shape probe connected to an LED and a photodetector. Bacterial detection was evaluated with the immunosensor immersed in a bacterial suspension in water with a known concentration. Here, we report on the sensitivity of a new optoelectronic configuration consisting of two POF U-shaped probes, one as the reference and the other as the immunosensor, for the detection of Escherichia coli. In addition, another methos of detection was tested where the sensors were calibrated in the air, before being immersed in a bacterial suspension and then read in the air. This modification improved sensor sensitivity and resulted in a faster detection time. After the immunocapture, the sensors were DAPI-stained and submitted to confocal microscopy. The histograms obtained confirmed that the responses of the immunosensors were due to the bacteria. This new sensor detected the presence of E. coli at 104 CFU/mL in less than 20 min. Currently, sub-20 min is faster than previous studies using fiber-optic based biosensors. We report on an inexpensive and faster detection technology when compared with conventional methods.

Microfluidic Sensor Based on Cell-Imprinted Polymer-Coated Microwires for Conductometric Detection of Bacteria in Water.

The rapid, inexpensive, and on-site detection of bacterial contaminants using highly sensitive and specific microfluidic sensors is attracting substantial attention in water quality monitoring applications. Cell-imprinted polymers (CIPs) have emerged as robust, cost-effective, and versatile recognition materials with selective binding sites for capturing whole bacteria. However, electrochemical transduction of the binding event to a measurable signal within a microfluidic device to develop easy-to-use, compact, portable, durable, and affordable sensors remains a challenge. For this paper, we employed CIP-functionalized microwires (CIP-MWs) with an affinity towards E. coli and integrated them into a low-cost microfluidic sensor to measure the conductometric transduction of CIP-bacteria binding events. The sensor comprised two CIP-MWs suspended perpendicularly to a PDMS microchannel. The inter-wire electrical resistance of the microchannel was measured before, during, and after exposure of CIP-MWs to bacteria. A decline in the inter-wire resistance of the sensor after 30 min of incubation with bacteria was detected. Resistance change normalization and the subsequent analysis of the sensor's dose-response curve between 0 to 109 CFU/mL bacteria revealed the limits of detection and quantification of 2.1 × 105 CFU/mL and 7.3 × 105 CFU/mL, respectively. The dynamic range of the sensor was 104 to 107 CFU/mL where the bacteria counts were statistically distinguishable from each other. A linear fit in this range resulted in a sensitivity of 7.35 μS per CFU/mL. Experiments using competing Sarcina or Listeria cells showed specificity of the sensor towards the imprinted E. coli cells. The reported CIP-MW-based conductometric microfluidic sensor can provide a cost-effective, durable, portable, and real-time solution for the detection of pathogens in water.

Emerging Applications of Nanobiosensors in Pathogen Detection in Water and Food.

Food and waterborne illnesses are still a major concern in health and food safety areas. Every year, almost 0.42 million and 2.2 million deaths related to food and waterborne illness are reported worldwide, respectively. In foodborne pathogens, bacteria such as Salmonella, Shiga-toxin producer Escherichia coli, Campylobacter, and Listeria monocytogenes are considered to be high-concern pathogens. High-concern waterborne pathogens are Vibrio cholerae, leptospirosis, Schistosoma mansoni, and Schistosima japonicum, among others. Despite the major efforts of food and water quality control to monitor the presence of these pathogens of concern in these kinds of sources, foodborne and waterborne illness occurrence is still high globally. For these reasons, the development of novel and faster pathogen-detection methods applicable to real-time surveillance strategies are required. Methods based on biosensor devices have emerged as novel tools for faster detection of food and water pathogens, in contrast to traditional methods that are usually time-consuming and are unsuitable for large-scale monitoring. Biosensor devices can be summarized as devices that use biochemical reactions with a biorecognition section (isolated enzymes, antibodies, tissues, genetic materials, or aptamers) to detect pathogens. In most cases, biosensors are based on the correlation of electrical, thermal, or optical signals in the presence of pathogen biomarkers. The application of nano and molecular technologies allows the identification of pathogens in a faster and high-sensibility manner, at extremely low-pathogen concentrations. In fact, the integration of gold, silver, iron, and magnetic nanoparticles (NP) in biosensors has demonstrated an improvement in their detection functionality. The present review summarizes the principal application of nanomaterials and biosensor-based devices for the detection of pathogens in food and water samples. Additionally, it highlights the improvement of biosensor devices through nanomaterials. Nanomaterials offer unique advantages for pathogen detection. The nanoscale and high specific surface area allows for more effective interaction with pathogenic agents, enhancing the sensitivity and selectivity of the biosensors. Finally, biosensors' capability to functionalize with specific molecules such as antibodies or nucleic acids facilitates the specific detection of the target pathogens.

Simultaneous detection of various pathogenic Escherichia coli in water by sequencing multiplex PCR amplicons

Waterborne diseases due to pathogen contamination in water are a serious problem all over the world. Accurate and simultaneous detection of pathogens in water is important to protect public health. In this study, we developed a method to simultaneously detect various pathogenic Escherichia coli by sequencing the amplicons of multiplex PCR. Our newly designed multiplex PCR amplified five genes for pathogenic E. coli (uidA, stx1, stx2, STh gene, and LT gene). Additional two PCR assays (for aggR and eae) were also designed and included in the amplicon sequencing analysis. The same assays were also used for digital PCR (dPCR). Strong positive correlations were observed between the sequence read count and the dPCR results for most of the genes targeted, suggesting that our multiplex PCR-amplicon sequencing approach could provide quantitative information. The method was also successfully applied to monitor the level of pathogenic E. coli in river water and wastewater samples. The approach shown here could be expanded by targeting genes for other pathogens.

Electrical Characterization of Cellulose-Based Membranes towards Pathogen Detection in Water.

Paper substrates are promising for development of cost-effective and efficient point-of-care biosensors, essential for public healthcare and environmental diagnostics in emergency situations. Most paper-based biosensors rely on the natural capillarity of paper to perform qualitative or semi-quantitative colorimetric detections. To achieve quantification and better sensitivity, technologies combining paper-based substrates and electrical detection are being developed. In this work, we demonstrate the potential of electrical measurements by means of a simple, parallel-plate electrode setup towards the detection of whole-cell bacteria captured in nitrocellulose (NC) membranes. Unlike current electrical sensors, which are mostly integrated, this plug and play system has reusable electrodes and enables simple and fast bacterial detection through impedance measurements. The characterized NC membrane was subjected to (i) a biofunctionalization, (ii) different saline solutions modelling real water samples, and (iii) bacterial suspensions of different concentrations. Bacterial detection was achieved in low conductivity buffers through both resistive and capacitive changes in the sensed medium. To capture Bacillus thuringiensis, the model microorganism used in this work, the endolysin cell-wall binding domain (CBD) of Deep-Blue, a bacteriophage targeting this bacterium, was integrated into the membranes as a recognition bio-interface. This experimental proof-of-concept illustrates the electrical detection of 107 colony-forming units (CFU) mL−1 bacteria in low-salinity buffers within 5 min, using a very simple setup. This offers perspectives for affordable pathogen sensors that can easily be reconfigured for different bacteria. Water quality testing is a particularly interesting application since it requires frequent testing, especially in emergency situations.

Emerging investigator series: bacteriophages as nano engineering tools for quality monitoring and pathogen detection in water and wastewater

Phase-based detection and monitoring of pathogens in water and wastewater.

Colorimetric and electrochemical detection of pathogens in water using silver ions as a unique probe

The manuscript highlights the efficacy of silver ions to act as a unique probe for the detection of bacterial contamination in water samples. The bacterial cell membrane adherence property of the silver ions was employed to develop two different bacterial detection assays employing colorimetric and electrochemical techniques. In one of the schemes, silver ion was used directly as a detector of bacteria in a colorimetric assay format, and in the other scheme surface-functionalized antibodies were used as a primary capture for specific detection of Salmonella enterica serovar Typhi. The colorimetric detection is based on silver-induced inhibition of urease activity and silver ion utilization by bacteria for the rapid screening of enteric pathogens in water. The specific detection of bacteria uses an antibody-based electrochemical method that employs silver as an electrochemical probe. The ability of silver to act as an electrochemical probe was investigated by employing Anodic Stripping Voltammetry (ASV) for targeted detection of Salmonella Typhi. For further insights into the developed assays, inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) studies were performed. The sensitivity of the developed assay was found to be 100 cfu mL−1 for colorimetric and 10 cfu mL−1 for electrochemical assay respectively.

Elucidating Waterborne Pathogen Presence and Aiding Source Apportionment in an Impaired Stream.

Fecal indicator bacteria (FIB) are the basis for water quality regulations and are considered proxies for waterborne pathogens when conducting human health risk assessments. The direct detection of pathogens in water and simultaneous identification of the source of fecal contamination are possible with microarrays, circumventing the drawbacks to FIB approaches. A multigene target microarray was used to assess the prevalence of waterborne pathogens in a fecally impaired mixed-use watershed. The results indicate that fecal coliforms have improved substantially in the watershed since its listing as a 303(d) impaired stream in 2002 and are now near United States recreational water criterion standards. However, waterborne pathogens are still prevalent in the watershed, as viruses (bocavirus, hepatitis E and A viruses, norovirus, and enterovirus G), bacteria (Campylobacter spp., Clostridium spp., enterohemorrhagic and enterotoxigenic Escherichia coli, uropathogenic E. coli, Enterococcus faecalis, Helicobacter spp., Salmonella spp., and Vibrio spp.), and eukaryotes (Acanthamoeba spp., Entamoeba histolytica, and Naegleria fowleri) were detected. A comparison of the stream microbial ecology with that of sewage, cattle, and swine fecal samples revealed that human sources of fecal contamination dominate in the watershed. The methodology presented is applicable to a wide range of impaired streams for the identification of human health risk due to waterborne pathogens and for the identification of areas for remediation efforts.IMPORTANCE The direct detection of waterborne pathogens in water overcomes many of the limitations of the fecal indicator paradigm. Furthermore, the identification of the source of fecal impairment aids in identifying areas for remediation efforts. Multitarget gene microarrays are shown to simultaneously identify waterborne pathogens and aid in determining the sources of impairment, enabling further focused investigations. This study shows the use of this methodology in a historically impaired watershed in which total maximum daily load reductions have been successfully implemented to reduce risk. The results suggest that while the fecal indicators have been reduced more than 96% and are nearing recreational water criterion levels, pathogens are still detectable in the watershed. Microbial source tracking results show that additional remediation efforts are needed to reduce the impact of human sewage in the watershed.

Investigating Membrane Material and Morphology for Development of Lateral Flow Biosensor

Development of membrane for bio–sensing applications, such as the detection of pathogens in drinking water for epidemics control has a huge global impact especially for public health. Membrane that applied in the bio–sensing devices should fulfill requirements such as high binding ability, fast lateral wicking time and low background staining. This paper explores the selection of membranes, including Nitrocellulose membrane (NC), Cellulose Acetate membrane (CA), Polyvinylidene Fluoride membrane (PVDF) and Nylon membrane for the detection of pathogens in water in the most efficient and rapid way. Membrane modification using glutaraldehyde enable the achieved of higher sensitivity of protein binding. Experimental findings (FTIR, porosity, membrane’s binding ability and lateral wicking time) verified the most suitable membrane for bio-sensing application. Among the tested membranes, NC appeared as the most suitable lateral flow membrane as its performances of high protein binding ability and fast lateral wicking time. Throughout this study, we showed the correlation of membrane’s material and morphology to its performances for pathogens detection in drinking water.

Design and Optimization of a Bacterial Sensor Based on the Innate Immune System

The rapid and accurate detection of bacteria is of great concern in both clinical and defence settings. However, to date, the gold standard in the detection of bacteria remains the method of culturing bacteria in a laboratory setting. This process is slow and laborious, often taking multiple days before confirmation is given. This delay between presentation and identification is detrimental in both settings, as patients could go untreated or, in the case of biological terrorism or warfare, many potential victims could be exposed to a pathogen. As such, there is a need for the development of a rapid and sensitive detection system capable of identifying the presence of bacteria outside of a clinical laboratory. In the human body, this function is fulfilled by the innate immune system, which responds to pathogen-associated molecular patterns (PAMPs) that are present on broad classifications of biological threats. For example, Toll-Like Receptor-4 (TLR-4), a pattern recognition receptor in the innate immune system, responds to the presence of lipopolysaccharide, the PAMP displayed on Gram-negative bacteria. As Gram-negative and Gram-positive bacteria can be treated with different antibiotics, even this broad distinction can be medically relevant. TLR-4 and the other proteins in the Toll-Like Receptor family have recently been studied for their use in biosensors1–5, and have shown great promise in being able to rapidly differentiate classes of bacteria and other biological threat agents. One major advantage over aptamer or antibody based sensors is that the user does not need to know what the biological agent is. Instead, the sensor can be used as a broad screening tool. This is especially true for the use of electrochemically based Toll-Like Receptor sensors, where the protein is attached to a surface via a linker, such as a self-assembled monolayer (SAM). However, these sensors have relied almost exclusively on the presence of relatively high resistance (> 1 kΩ) systems that provide small signals that are ill-suited to implementation outside of a laboratory1. To address this deficiency, we sought to optimize a TLR-4/SAM-based biosensor. Towards this aim, we have built upon previous work in which TLR-4 is oriented in a bio-mimicking fashion on a Au electrode surface1. The protein was tethered to a Ni2+-nitrilitriacetic acid (NTA) functional group, covalently attached to the end of a carboxyl-terminated thiol-based SAM. Various SAMs were explored in this work, ranging from long-chain single-component monolayers to tripartite SAMs containing multiple functional groups. An optimal ratio of thiol components was determined, based on the TLR-4 sensor response to the presence of Gram-negative bacteria, while remaining insensitive to the presence of Gram-positive bacteria or viral particles, with all samples presenting ≤1 kΩ of interfacial resistance to the rectification reaction. This represents a marked decrease in resistance compared to the current state-of-the-art for TLR-based sensors, providing a convenient avenue for future studies. 1. Mayall, R. M., Renaud-Young, M., Chan, N. W. C. & Birss, V. I. An electrochemical lipopolysaccharide sensor based on an immobilized Toll-Like Receptor-4. Biosens. Bioelectron. 87, 794–801 (2017). 2. Amini, K., Chan, N. W. C. & Kraatz, H.-B. Toll-like receptor 3 modified Au electrodes: an investigation into the interaction of TLR3 immobilized on Au surfaces with poly(I:C). Anal. Methods 6, 3322 (2014). 3. She, Z. et al. Investigation of the utility of complementary electrochemical detection techniques to examine the in vitro affinity of bacterial flagellins for a toll-like receptor 5 biosensor. Anal. Chem. 150222112048003 (2015). doi:10.1021/ac5042439 4. Amini, K. & Kraatz, H.-B. Toll-like receptors for pathogen detection in water: challenges and benefits. Int. J. Environ. Anal. Chem. 7319, 1–9 (2016). 5. Yeo, T. Y. et al. Electrochemical endotoxin sensors based on TLR4/MD-2 complexes immobilized on gold electrodes. Biosens. Bioelectron. 28, 139–145 (2011).

Wireless Sensors and Actuators Based on Magnetostrictive Resonators

Biosensors based on magnetostrictive resonators, magnetostrictive cantilever and magnetostrictive particles (MSPs), have been developed in recent years [1]. Due to their magnetic nature, these biosensors are wireless, which makes them to a great candidate for in-situ detection. Both phage and antibody, which are immobilized onto the surface of the magnetostrictive resonator, have been used as biological molecular recognition elements. The performance characterization of these biosensors shows that these biosensors work well in liquid and exhibit a high sensitivity for the detection of bacteria in water [2].It is well known that the sensitivity of MSP increases with reducing size of the MSP. Therefore, a much better sensitivity is expected for the MSPs with a smaller size. The above results demonstrate that the biosensors based on the magnetostrictive resonators are suitable for in-situ detection of pathogens in liquid media. To fully develop the detection technology based on magnetostrictive resonators for in-field detection, a small size interrogation unit/device is required. A new methodology was developed recently [3]. Based on this technology, a handheld device is developed to characterize the response of the biosensors based on magnetostrictive resonators.For the detection of pathogenic species in food samples, sampling is always a key issue, since the locations of the target species are unknown and the biosensors have to be brought into reaction with the target species. It is experimentally found that an MSP biosensor can act as an actuator when it is driven under a frequency different than the resonant frequency. In the experiments, it is found that the moving speed of the MSP actuator is dependent on the frequency. A freestanding MSP is an actuator that can move along its length direction without the limitation in displacement and the motion can be both directions.REFERENCES[1] K. W. Zhang, L. Zhang, L. L. Fu, S. Q. Li, H. Q. Chen, and Z.-Y. Cheng, Magnetostrictive resonators as sensors and actuators, Sensors & Actuators: A. Physical, 200, 2-10 (2013).[2] K. W. Zhang, L. L. Fu, L. Zhang, Z.-Y. Cheng, and T.-S. Huang, Magnetostrictive particle based biosensors for in-situ and real-time detection of pathogens in water, Biotechnology and Bioengineering, 111, 2229 (2014).[3] Z.Y. Cheng, A.X. Zhang, K.W. Zhang, B.A. Chin, Systems for Characterizing Resonance Behavior of Magnetostrictive Resonator(s), U.S. Patent Application No. 20120280682 (2012).

An integrated passive-flow microfluidic biosensor with organic photodiodes for ultra-sensitive pathogen detection in water.

This work reports on integrated passive-flow optical microfluidic devices to detect waterborne pathogens in the field. Ring-shaped organic photodiodes were integrated to a capillary-induced flow microfluidic channel for monitoring chemiluminescent sandwich immunoassays enhanced by gold nanoparticles. The integrated device yielded a resolution of 4×10(4) cells/mL for the detection of Legionella pneumophila, which represented a 25-fold improvement over chemiluminescence detection devices employing no gold-nanoparticle enhancement. This work demonstrates the feasibility of a low-cost but highly sensitive lab-on-a-chip device amenable for point-of-use applications.

The impact of major earthquakes and subsequent sewage discharges on the microbial quality of water and sediments in an urban river

A series of large earthquakes struck the city of Christchurch, New Zealand in 2010–2011. Major damage sustained by the sewerage infrastructure required direct discharge of up to 38,000m3/day of raw sewage into the Avon River of Christchurch for approximately six months. This allowed evaluation of the relationship between concentrations of indicator microorganisms (Escherichia coli, Clostridium perfringens and F-RNA phage) and pathogens (Campylobacter, Giardia and Cryptosporidium) in recreational water and sediment both during and post-cessation of sewage discharges.Giardia was the pathogen found most frequently in river water and sediment, although Campylobacter was found at higher levels in water samples. E. coli levels in water above 550CFU/100mL were associated with increased likelihood of detection of Campylobacter, Giardia and Cryptosporidium, supporting the use of E. coli as a reliable indicator for public health risk. The strength of the correlation of microbial indicators with pathogen detection in water decreased in the following order: E. coli>F-RNA phage>C. perfringens.All the microorganisms assayed in this study could be recovered from sediments. C. perfringens was observed to accumulate in sediments, which may have confounded its usefulness as an indicator of fresh sewage discharge. F-RNA phage, however, did not appear to accumulate in sediment and in conjunction with E. coli, may have potential as an indicator of recent human sewage discharge in freshwater. There is evidence to support the low-level persistence of Cryptosporidium and Giardia, but not Campylobacter, in river sediments after cessation of sewage discharges. In the event of disturbances of the sediment, it is highly probable that there could be re-mobilisation of microorganisms beyond the sediment–water exchange processes occurring under base flow conditions. Re-suspension events do, therefore, increase the potential risk to human health for those who participate in recreational and work-related activities in the river environment.

Fabrication of multi-layer polymeric micro-sieve having narrow slot pores with conventional ultraviolet-lithography and micro-fabrication techniques

Fast detection of waterborne pathogens is important for securing the hygiene of drinking water. Detection of pathogens in water at low concentrations and minute quantities demands rapid and efficient enrichment methods in order to improve the signal-to-noise ratio of bio-sensors. We propose and demonstrate a low cost and rapid method to fabricate a multi-layer polymeric micro-sieve using conventional lithography techniques. The micro-fabricated micro-sieves are made of several layers of SU-8 photoresist using multiple coating and exposure steps and a single developing process. The obtained micro-sieves have good mechanical properties, smooth surfaces, high porosity (≈40%), and narrow pore size distribution (coefficient of variation < 3.33%). Sample loading and back-flushing using the multi-layer micro-sieve resulted in more than 90% recovery of pathogens, which showed improved performance than current commercial filters.

Atlantis Mobile Laboratory for Population Survey

P-526 Introduction: The Atlantis Mobile Laboratory was created as a novel, unique infrastructure to meet emerging environmental and health challenges in remote settings. This self sufficient laboratory can travel by boat or ground transportation to any destination that needs complete laboratory facilities for field-based environmental monitoring, environmental health issues or research activities in related disciplines. The facility comprises modules built in standard size containers. Three modules are laboratories (microbiology, analytical chemistry, and biochemistry/cell culture) and three others are dedicated to support the facility and transport of material. Objectives: The objectives of Atlantis are environmental and public health monitoring, prevention and intervention in any remote country districts. The Atlantis scientists use new, easy-to-utilize techniques to measure the concentrations and assess the effects of environmental contaminants, natural toxins and pathogens that may threaten public health and the ecosystem. Human toxicology, ecotoxicology and environmental microbiology studies are also carried out. Moreover, the mobile laboratory promotes and facilitates the interaction and training with local professionals, researchers and science students, as well as education and technology transfer dedicated to children and the general public. Research and education activities. The first pilot study of Atlantis was conducted during fall 2003 in Bermuda where a well-equipped research station supported the field work. The following program was conducted within a two-month period and include the following components: A prenatal assessment of human exposure to persistent organic pollutants and heavy metals, an ecotoxicology study on the local marine fauna in a semi-immerged dump site, an assessment of drinking water microbiological quality in Bermudas homes, the development of new polymerase chain-reaction techniques for the rapid detection of pathogens in water and the implementation and testing of an integrated database using Geographic Information System tools. Results of these assessments were available to the population and government agencies in setting priorities for action. The second mission, in collaboration with ArcticNet (a network of Arctic researchers), was conducted in the 14 communities of Nunavik (Northern Québec, Canada), on the ice-breaker Amundsen, during fall 2004. Two Atlantis units were used on the ship to detect neurotoxicity markers in the Inuit population, conduct cytogenetic damage analyses in lymphocytes in relation to food-chain contaminant exposure, and to investigate the contamination of freshwater ecosystems. The third mission was conducted in Mistissini, a Cree community of the James Bay Territory (Northern Québec, Canada), during summer 2005. The aims were to conduct on site analyses of some environmental contaminants, to investigate the contamination of freshwater ecosystems and to promote efficient communication and education on sciences and health issues to youth.

Quantification of human astroviruses in sewage using real-time RT-PCR

Human astroviruses constitute a significant cause of acute diarrhea in children. Viral transmission occurs via the fecal–oral route, predominantly person-to-person, but the consumption of fecally contaminated water and shellfish has also been implicated. Viral pathogen detection in water, especially, in wastewater, is difficult and PCR is widely used to detect these viruses. Despite the recent development of real-time quantitative PCR, quantification of astroviruses in sewage had not been available up to now. We have developed a method to quantify astroviruses in sewage. For this purpose, we designed a set of primers and a fluorogenic probe located at the 3′-end of the genome of human astroviruses. The amplified region was cloned and the plasmid was transcribed to generate calibration standards for quantification. After validation of the standards, the method was evaluated in artificially contaminated samples. To validate the method on naturally contaminated samples, raw and treated wastewater samples were collected monthly for one year in a sewage treatment plant. Astrovirus genomes were detected in all samples collected at the entrance to the sewage treatment plant, with a mean value of 4.1×10 6 astrovirus genomes for 100 ml. Effluents were less strongly contaminated, with a mean value of 1.01×10 4 astrovirus genomes. The high prevalence of astroviruses in sewage treatment plant effluents indicates that these plants are not efficiently eliminating the virus. This is a major public health concern and new techniques of depuration are needed. Our method could be effectively used in evaluating new treatment processes to reduce the viral load in the effluent of treatment plants.

Pathogenic agents in freshwater resources

Numerous pathogenic agents have been found in freshwaters used as sources for water supplies, recreational bathing and irrigation. These agents include bacterial pathogens, enteric viruses, several protozoans and parasitic worms more common to tropical waters. Although infected humans are a major source of pathogens, farm animals (cattle, sheep, pigs), animal pets (dogs, cats) and wildlife serve as significant reservoirs and should not be ignored. The range of infected individuals within a given warm-blooded animal group (humans included) may range from 1 to 25%. Survival times for pathogens in the water environment may range from a few days to as much as a year (Ascaris, Taenia eggs), with infective dose levels varying from one viable cell for several primary pathogenic agents to many thousands of cells for a given opportunistic pathogen. As pathogen detection in water is complex and not readily incorporated into routine monitoring, a surrogate is necessary. In general, indicators of faecal contamination provide a positive correlation with intestinal pathogen occurrences only when appropriate sample volumes are examined by sensitive methodology. Pathways by which pathogens reach susceptible water users include ingestion of contaminated water, body contact with polluted recreational waters and consumption of salad crops irrigated by polluted freshwaters. Major contributors to the spread of various water-borne pathogens are sewage, polluted surface waters and stormwater runoff. All of these contributions are intensified during periods of major floods. Several water-borne case histories are cited as examples of breakdowns in public health protection related to water supply, recreational waters and the consumption of contaminated salad crops. In the long term, water resource management must focus on pollution prevention from point sources of waste discharges and the spread of pathogens in watershed stormwater runoff.

Application of the Polymerase Chain Reaction Technique to the Detection of Pathogens in Water

Enteric pathogens may be present in fecally contaminated waters at extremely low concentrations. In addition, these pathogens may be injured when exposed to the environment and may not be able to grow in laboratory culture media or such media may simply not exist for their progagation in the laboratory. It is paramount thus to use techniques which do not depend on culture techniques for the detection of these pathogens and that allow for the detection of single-cell concentrations. The polymerase chain reaction (PCR) technique has been shown to be an excellent and sensitive means of detecting pathogens in waters. Membrane filtration has been combined with PCR and DNA hybridization techniques to be able to detect the DNA equivalent of one single cell in large volumes of water. In addition, this combination of methods allows for the amplification of different target genes fiat may be present in the sample, since the membrane can be subjected to repeated amplification reactions under different conditions. A Most Probable Number PGR was developed which allows for the quantification of gene copy number and thus permits extrapolation to estimate the number of bacterial cells in the original sample.