Coli In Water Research Articles

Aptamer Functionalized ZnO Thin-Film Transistor Based Multiplexed Detection of Pb and E. Coli in Water

In this work, we demonstrate the multiplexed detection platform to sense lead (Pb2+) and Escherichia coli in water using zinc oxide (ZnO) thin-film transistors (TFTs). Low-voltage ZnO TFTs fabricated by physical vapor deposition were functionalized with (3-Aminopropyl)triethoxysilane (APTES)–glutaraldehyde (GLU) molecules. TFTs with such functionalized ZnO surfaces showed good sensitivity and high specificity to the targets with a detection limit of 27 nM and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula> colony forming unit per mL (cfu/mL) for Pb2+ and E. coli, respectively, with the TFT flat-band voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\text {fb}}$ </tex-math></inline-formula> ) and, hence, the TFT transconductance, being dependent on the target concentration. The direct integration of the sensing with the TFT and associated integrated circuits promises high-density sensor arrays.

False Positive Analysis Using the Enzymatic Substrate Method for Detection of Escherichia Coli in Water from Rural Communities

False Positive Analysis Using the Enzymatic Substrate Method for Detection of Escherichia Coli in Water from Rural Communities

Activation of Persulfate by Fecl3-Activated Biochar for Disinfection of Escherichia Coli in Water

Activation of Persulfate by Fecl3-Activated Biochar for Disinfection of Escherichia Coli in Water

Sensitive detection of E. coli using bioconjugated fluorescent silica nanoparticles

Fluorescent dye-doped silica nanoparticles have been a major focus of research and development as potential fluorescent probes in biological systems. This is due to their strong fluorescence intensity, excellent photostability, biocompatibility, and ease of surface modification for bioconjugation. In this study, spherical silica nanoparticles doped with fluorescein isothiocyanate (FITC) were synthesized using reverse microemulsion method. The average diameter of the nanoparticles was 78 nm with a narrow size distribution (78 ± 49.50 nm). FITC was incorporated into the silica sphere through 3-aminopropyltriethoxysilane, which minimized the leakage of the dye. Only about 30% of the dye leaked out from these nanoparticles, after they were sonicated in aqueous medium for 60 min and the fluorescent intensity remained comparatively constant over time, showing an increased photostability (∼ 1.5 times higher) compared to the free dye in solution. The fluorescence emission spectrum of nanoparticles showed no apparent shift (maximum emission at 518 nm) when compared with the free dye in solution. The nanoparticle surface was chemically modified with amine and carboxyl functionalities to allow for Escherichia coli antibody conjugation. E. coli bacteria is widely used as a biological indicator to identify fecal contamination in food and water samples. Nanoparticle-based biosensors for the detection of E. coli have a vital importance in water quality, public health, and food safety. The E. coli in water was successfully observed under a fluorescence microscope using the antibody conjugated fluorescent silica nanoparticles synthesized, proving the feasibility of using them in a biosensor for qualitative determination of E. coli. The significance of this study lies in the relatively simple synthetic procedures as compared to those that have been in other studies reported in the literature. The ability to detect live cells under the fluorescence microscope further proves the suitability of these functionalized nanoparticles in live cell imaging.

Outer‐Membrane Protease (OmpT) Based E. coli Sensing with Anionic Polythiophene and Unlabeled Peptide Substrate

AbstractE. coli and Salmonella are two of the most common bacterial pathogens involved in foodborne and waterborne related deaths. Hence, it is critical to develop rapid and sensitive detection strategies for near‐outbreak applications. Reported is a simple and specific assay to detect as low as 1 CFU mL−1 of E. coli in water within 6 hours by targeting the bacteria's surface protease activity. The assay relies on polythiophene acetic acid (PTAA) as an optical reporter and a short unlabeled peptide (LL37FRRV) previously optimized as a substrate for OmpT, an outer‐membrane protease on E. coli. LL37FRRV interacts with PTAA to enhance its fluorescence while also inducing the formation of a helical PTAA‐LL37FRRV construct, as confirmed by circular dichroism. However, in the presence of E. coli LL37FRRV is cleaved and can no longer affect the conformations and optical properties of PTAA. This ability to distinguish between an intact and cleaved peptide was investigated in detail using LL37FRRV sequence variants.

Design of ultra-high sensitive biosensor to detect E. Coli in water

Escherichia coli (abbreviated as E. coli) are bacteria found in water, in food. The present work focuses applications of surface plasmon resonance (SPR) based biosensors to detect E. coli. SPR is a label-free technology that is used to detect biological samples. The SPR based biosensor design consists of optical wave guide with different structures of metal–dielectric interfaces and effort has been done to optimize design parameters for improved sensitivity. Metal-dielectric structures considered are Au–Si, Ag–Si, Au–GaAs and Ag–GaAs. Obtained simulation results indicates that the performance of the proposed sensor can be enhanced by varying the thickness and material of metal–dielectric interfaces. The device sensitivity obtained 1071.42 nm/RIU by considering metal-dielectric interface of Gold (thickness 0.074 μm) and Gallium Arsenide (thickness 0.22 μm). This result is significantly higher than sensitivity value of 250 nm/RIU found in published literature for similar type of sensor. From the simulation graph it is clear that for small change in refractive index (RI), value of 0.07 (1.33–1.4), there is significant shift in wavelength. This shows that the sensor is highly sensitive towards the change in RI and can be fabricated as lab-on-chip based biosensor. The optimized sensor was tested for detection for E. coli and sensitivity of 400 nm/RIU obtained. The design is compact and easy to fabricate using optical lithography as compared to the conventional optical component based SPR sensor.

Evaluation of the novel substrate RUG™ for the detection ofEscherichia coliin water from temperate (Zurich, Switzerland) and tropical (Bushenyi, Uganda) field sites

The assessment of a novel enzyme-based assay showed it to be reliable to detect and quantifyE. coliin water.

Water for African elephants (Loxodonta africana): faecal microbial loads affect use of artificial waterholes.

In semi-arid protected areas, artificial waterholes ensure that water is locally available to animals for extended periods. However, artificial waterholes may limit animal movement, which contributes towards habitat deterioration. Challenges of artificial water provisioning worsen in the presence of ecosystem engineers like African elephants Loxodonta africana, capable of transforming environments. Camera traps were used to monitor elephant visitation at 21 artificial waterholes in the Kruger National Park, South Africa. We also assessed if water quality parameters influenced elephant preference for certain waterholes. There were no significant correlations between elephant abundance and water physicochemical properties. However, there was a strong negative correlation between elephant abundance and levels of Escherichia coli in water. Our findings suggest that elephants avoid drinking water with high levels of faecal microbial loads. Whereas most studies addressing animal management in protected areas consider waterholes as homogeneous units, we posit that water quality could also determine local landscape use and movement patterns of key species like elephants, a finding with relevant implications in reserve management practices.

Electrochemical disinfection of coliform and Escherichia coli for drinking water treatment by electrolysis method using carbon as an electrode

Disinfection of coliform and E. Coli in water has been performed by electrolysis using carbon electrodes. Carbon electrodes were used as an anode and cathode with a purity of 98.31% based on SEM-EDS analysis. This study was conducted using electrolysis powered by electric field using carbon electrode as the anode and cathode. Electrolysis method was carried out using variations of time (30, 60, 90, 120 minutes at a voltage of 5 V) and voltage (5, 10, 15, 20 V for 30 minutes) to determine the effect of the disinfection of the bacteria. The results showed the number of coliform and E. coli in water before and after electrolysis was 190 and 22 MPN/100 mL, respectively. The standards quality of drinking water No. 492/Menkes/Per/IV/2010 requires the zero content of coliform and E. Coli. Electrolysis with the variation of time and potential can reduce the number of coliforms and E. Coli but was not in accordance with the standards. The effect of hydrogen peroxide (H2O2) to the electrochemical disinfection was determined using UV-Vis spectrophotometer. The levels of H2O2 formed increased as soon after the duration of electrolysis voltage but was not a significant influence to the mortality of coliform and E.coli.

Culture-dependent enumeration methods failed to simultaneously detect disinfectant-injured and genetically modified Escherichia coli in drinking water.

Underestimation of Escherichia coli in drinking water, an indicator microorganism of sanitary risk, may result in potential risks of waterborne diseases. However, the detection of disinfectant-injured or genetically modified (GM) E. coli has been largely overlooked so far. To evaluate the accuracy of culture-dependent enumeration with regard to disinfectant-injured and GM E. coli, chlorine- or ozone-injured wild-type (WT) and GM E. coli were prepared and characterized. Then, water samples contaminated with these E. coli strains were assayed by four widely used methods, including lactose tryptose broth-based multiple-tube fermentation (MTF), m-endo-based membrane filtration method (MFM), an enzyme substrate test (EST) known as Colilert, and Petrifilm-based testing slip method (TSM). It was found that MTF was the most effective method to detect disinfectant-injured WT E. coli (with 76.9% trials detecting all these bacteria), while this method could not effectively detect GM E. coli (with uninjured bacteria undetectable and a maximal detection rate of 21.5% for the injured). The EST was the only method which enabled considerable enumeration of uninjured GM E. coli, with a detection rate of over 93%. However, the detection rate declined to lower than 45.4% once the GM E. coli was injured by disinfectants. The MFM was invalid for both disinfectant-injured and GM E. coli. This is the first study to report the failure of these commonly used enumeration methods to simultaneously detect disinfectant-injured and GM E. coli. Thus, it highlights the urgent requirement for the development of a more accurate and versatile enumeration method which allows the detection of disinfectant-injured and GM E. coli on the assessment of microbial quality of drinking water.

The Study on the Survival of Escherichia Coli in Water at Room Temperature

Escherichia coli (E. coli) is one of the most frequent causes of many bacterial infections especially gastroenteritis in developing countries. It is also used as an indicator for faecal pollution in the surveillance of bacteriological quality of drinking water. This study was conducted to determine the survival of E. coli in water at room temperature (27oC). E. coli which is cultured in Lactose Peptone Broth was inoculated into 8 bottles each containing 10 millilitres of distilled water. They were kept at 27oC. Starting from the day 1, ten-fold dilutions were made from each bottle number and E. coli count was done from each dilutions by using pour plate method. The colony forming unit/ millilitre (CFU/ml) was calculated. The same procedure was carried out from bottles number 2 to 8 from day 2 to day 8 consecutively. CFU/ml of E. coli in dilution 10-5was markedly decreased from 3.9 x 106 in day 1to 0 in day 8. The findings suggest that if the water is contaminated with low number of E. coli, it can be eliminated by keeping water at room temperature for only few days.

A Fluorescence Based Sensor System for Automated Detection of E. Coli in Water

Escherichia coli are indicator bacteria for water quality. The conventional method for detection is based on cultivation of E. coli, which takes up to 3 days. The goal of this study was the development of a sensor system for a fast and automated detection and quantification of E. coli in drinking water. Therefore, living E. coli bacteria were specifically labelled with fluorescence probes targeting the E. coli DNA. The culture of labelled bacteria was automatically scanned by an optical fluorescence microscope. With sophisticated image processing algorithms, the amount of E. coli bacteria on the filter was counted. Finally, the user of the system received a summarized report of the detected E. coli colonies in the sample. The total culturing and analysis time for one water sample takes about 16 hours and therefore, is much faster than conventional methods.

An automated, Robotic Biosensor for the Electrochemical Detection of E. Coli in Water

Escherichia coli are indicator bacteria for fecal contamination in water. The goal of our study was the implementation of an assay for voltammetric detection of E. coli into an automated instrument. Furthermore, this electrochemical biosensor works as a stand-alone instrument with on-line data transfer to monitor and control the water quality and to enhance treatment measures.The device performs automated water sample filtrations, followed by addition of growth media to the filter unit. After an incubation step, a defined sample aliquot is transferred on a screen printed electrode. The result of the electrochemical measurement indicates the presence of E. coli. The device output was compared with laboratory analysis. With the designed instrument it was possible to detect 5 colony forming units (CFU) of E. coli in 5ml within 18hours.

Use of Personal Glucose Meters for the Detection of E. Coli in Water

We have demonstrated the applicability of personal glucose meters for regularly monitoring the bacteriological quality of potable water. The detection principle is based on the preferred consumption of glucose by E.coli, which is measured using a personal glucose meter. The drop in glucose concentrations over time was correlated to the concentration of E.coli. We could accurately detect higher levels of contamination (~2x108 CFU) within 1 hr and extremely low levels of contamination (~2 CFU) within a maximum of 8 hr. The method presented is simple, inexpensive, easy to use and has the potential to be developed into a comprehensive test kit, which can provide both qualitative and quantitative results.

Use of Personal Glucose Meters for the Detection of E. Coli in Water

Contamination of potable water with pathogenic bacteria such as Escherichia coli (E.coli) is a major concern in the developing countries. Often water is consumed without any prior treatment leading to several water borne ailments such as diarrhea. According to United States Environmental Protection Agency (USEPA), the total concentration of E.coli in potable water should be restricted to 0 Colony Forming Units (CFU) per 100 ml of water for potable water and 126 CFU/100ml for recreational water. The conventional methods of pathogen detection generally involve transporting the contaminated water samples to centralized laboratories where detection and quantification techniques are based on instant culturing of bacteria, enzymatic reactions, and molecular (immunological or genetic) methods of detection. These processes often take 24 – 48 hours to produce results and are often expensive due to the additional requirements of resources and qualified personnel. Such a system for water monitoring is not suitable for low-resource settings. Rapid, easy to use and inexpensive detection systems need to be developed in order to empower individual households to regularly monitor their bacteriological water quality.One of the best examples of such rapid and simple detection systems is the Personal Glucose meter (PGM), which is used by patients with diabetes to regularly monitor their blood glucose levels. This system is based on an electrochemical reaction where in the glucose present in the sample is made to react with an enzyme electrode containing glucose oxidase and the resulting change in the current is measured, which in turn can be correlated to the concentration of the glucose. We have developed a simple method for the detection of E.coli and total coliform using PGMs by monitoring the consumption of glucose as a carbon source by E.coli during their growth cycle. Contaminated water samples with bacterial concentrations in the range of 2-2x108 CFU/mL were supplied with glucose solutions with known concentrations and Lauryl Tryptose (LT) broth as the growth medium in order to induce the consumption of glucose by E.coli. The drop in glucose concentrations in these samples was measured every hour with a PGM. It was observed that samples with very high concentrations of E.coli (2x106 - 2x108 CFU/mL) showed a drop in the glucose concentrations within an hour and samples with extremely low E.coli concentrations (2 CFU/mL) showed a drop in glucose concentrations within a maximum of 8 hours. This method can provide qualitative as well as quantitative results to determine the level of contamination in potable water. The time required to produce results with this method is much lower than the conventional colony counting method and the cost involved is quite less compared to the equipment required for ELISA plate readers. The current PGMs available in the market are portable and can produce reliable quantitative results. These systems are quite robust, simple and can be used by any untrained person. PGMs have also been recently integrated with smart phones thereby resulting in a further increase in their base of users. The E.coli detection kit presented here is simple, easy to use, reliable, cost effective and does not involve any toxic reagents or end products. This method doesn’t warrant any special training and can be used by any unskilled person on site at the source of water.

Use of plasma gliding arc discharges on the inactivation of E. Coli in water

The objective of the present study was to investigate the feasibility of using a gliding arc (GA) discharge to inactivate microorganisms in water. Microbubble generators were utilized to uniformly disperse gas bubbles that contain H2O2 in water. In addition, the residual effect of H2O2 in plasma-treated water was assessed by continuous quantitative measurement of microbiological colony forming units (cfu) in water after the completion of GA discharge. Application of the GA plasma discharge to water decreased pH from 6.15 to 3.55 after 25-min treatment, and the lowered pH was maintained for 4h after treatment ceased. The present study showed a total 6-log reduction in the cfu counts of Escherichia Coli with plasma treatment of 25min duration: 4-log reduction from 106 to 102 during treatment and an additional 2-log reduction from 102 to 100 during the 2h after treatment. The use of microbubble generators significantly enhanced the benefit of H2O2 in acidic water, increasing the bacterial inactivation ability of the plasma treatment with GA discharge.

Inactivation of E. Coli in Water Using Photocatalytic, Nanostructured Films Synthesized by Aerosol Routes

TiO2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO2 films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth’s surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water.

Evaluating the Pathogenic Potential of Environmental Escherichia coli by Using the Caenorhabditis elegans Infection Model

The detection and abundance of Escherichia coli in water is used to monitor and mandate the quality of drinking and recreational water. Distinguishing commensal waterborne E. coli isolates from those that cause diarrhea or extraintestinal disease in humans is important for quantifying human health risk. A DNA microarray was used to evaluate the distribution of virulence genes in 148 E. coli environmental isolates from a watershed in eastern Ontario, Canada, and in eight clinical isolates. Their pathogenic potential was evaluated with Caenorhabditis elegans, and the concordance between the bioassay result and the pathotype deduced by genotyping was explored. Isolates identified as potentially pathogenic on the basis of their complement of virulence genes were significantly more likely to be pathogenic to C. elegans than those determined to be potentially nonpathogenic. A number of isolates that were identified as nonpathogenic on the basis of genotyping were pathogenic in the infection assay, suggesting that genotyping did not capture all potentially pathogenic types. The detection of the adhesin-encoding genes sfaD, focA, and focG, which encode adhesins; of iroN2, which encodes a siderophore receptor; of pic, which encodes an autotransporter protein; and of b1432, which encodes a putative transposase, was significantly associated with pathogenicity in the infection assay. Overall, E. coli isolates predicted to be pathogenic on the basis of genotyping were indeed so in the C. elegans infection assay. Furthermore, the detection of C. elegans-infective environmental isolates predicted to be nonpathogenic on the basis of genotyping suggests that there are hitherto-unrecognized virulence factors or combinations thereof that are important in the establishment of infection.

Pathogenic Escherichia coli Found in Sewage Treatment Plants and Environmental Waters

We previously demonstrated that some Escherichia coli strains with uropathogenic properties survived treatment stages of sewage treatment plants (STPs), suggesting that they may be released into the environment. We investigated the presence of such strains in the surrounding environmental waters of four STPs from which these persistent strains were isolated. In all, 264 E. coli isolates were collected from 129 receiving water sites in a 20-km radius surrounding STPs. We also included 93 E. coli strains collected from 18 animal species for comparison. Isolates were typed using a high-resolution biochemical fingerprinting method (the PhPlate system), and grouped into common (C) types. One hundred forty-seven (56%) environmental isolates were identical to strains found in STPs' final effluents. Of these, 140 (95%) carried virulence genes (VGs) associated with intestinal pathogenic E. coli (IPEC) or uropathogenic E. coli (UPEC) and were found in a variety of sites within areas sampled. Of the remaining 117 environmental strains not identical to STP strains, 105 belonged to 18 C types and 102 of them carried VGs found among IPEC or UPEC strains. These strains belonged mainly to phylogenetic groups A (A0 and A1) and B1 and to a lesser extent B2(2), B2(3), D1, and D2. Eight of 18 environmental C types, comprising 50 isolates, were also identical to bird strains. The presence of a high percentage of environmental E. coli in waters near STPs carrying VGs associated with IPEC and UPEC suggests that they may have derived from STP effluents and other nonpoint sources.

Effects of H2O2 and Low pH Produced by Gliding Arc Discharge on the Inactivation of Escherichia Coli in Water

The efficacy of gliding arc (GA) discharge for the generation of hydrogen peroxide (H2O2) and water with a low pH was studied because H2O2 combined with low-pH environment is known as a strong oxidizer that can be used for the bacterial inactivation. The ability of the GA discharge to inactivate Escherichia coli in water was tested experimentally, and the inactivation was found to increase with the plasma treatment time and rate of water injection flow to the GA discharge system. The best result showed a 2-log reduction of the number of colony-forming units of E. coli from 104 to 102 at a water injection flow rate of 180 mL/min. Furthermore, pH in the plasma-treated water was decreased from 6.0 to 3.55 after 25 min of treatment.