Waterborne Bacteria Research Articles

Mechanism study of the impact of Escherichia coli on coal flotation.

Escherichia coli as water-borne bacteria exists in the recirculation water of coal flotation and affects the recovery of coal flotation. In order to study the effect of Escherichia coli on coal flotation, we changed the concentration of Escherichia coli and pH in the coal flotation system and found that Escherichia coli had an adverse effect on coal flotation. The concentration of Escherichia coli was negatively correlated with the recovery of coal. When the concentration of Escherichia coli reached 5.0 × 109 cells/ml, the recovery of coal flotation was 50.25%, and the change of pH basically did not affect the adverse effect of Escherichia coli on coal flotation. The mechanism was studied through Zeta potential, Fourier transform infrared spectroscopy, Scanning electron microscopy and Contact angle measurements. The results revealed that Escherichia coli could be adsorbed to the coal surface by hydrogen bonding, which changed the hydrophobicity of the coal surface and then reduced the recovery of coal flotation.

Photocatalytic disinfection of multidrug resistant staphylococcus haemolyticus and Escherichia coli using visible-LED: A photochemical approach to curb nosocomial infection

Undeniably, emergence of multidrug resistance (MDR) in water borne bacteria is the cataclysmic threat to global public health and may plunge the human civilization back to pre-antibiotic era. With limited technologies proven effective against MDR bacteria, there is an irrefutable need to demonstrate alternative and cost effective water disinfection strategies. In the present study, we have scrutinized the effectivity of Zinc Oxide–Kaolinite nanocomposites (ZnO–K),coated on sodium alginate beads (ZnO/K@alginate) for photocatalytic disinfection (PCD) of multi drug resistant Staphylococcus haemolyticus and Escherichia coli under visible-light emitting diode (LED). Under the same operational conditions, ZnO–K​ NC is found to have better efficiency than other photocatalysts [ZnO nanoparticles (NP)’s, Kaolinite, TiO 2 -Degussa P25] and traditional disinfection techniques (chlorination, hydrogen peroxide treatment, iodination, UV-C treatment). Impairment of bacterial cell membrane is supported by observation of lipid peroxidation and leakage of intracellular components to the reaction system. Additionally, fluoresces and electron microscopy established the detrimental effects on membrane integrity. Experimental evidences suggested that the hydrogen peroxide could be the principal reactive oxygen species involved in the PCD of the targeted bacteria. X-ray diffraction and atomic absorption spectroscopy indicated that ZnO/K@alginate beads could be reused for three consecutive cycles which suggests that the process may be explored for real world application to restrict the spread of nosocomial infection.

Visible light active graphene oxide modified Ag/Ag2O/BiPO4/Bi2WO6 for photocatalytic removal of organic pollutants and bacteria in wastewater

Wastewater problems caused by antibiotics and bacteria contamination have become the primary environmental concern due to their harm to terrestrial organisms and health risk. To obtain the efficient removal approach of antibiotics and bacteria, visible driven advanced oxidation process by photocatalyst for the efficient removal and reducing waterborne disease was demonstrated in this study. 2D/2D GO−Ag/P/BWO heterostructure photocatalyst (GO: graphene oxide, Ag: Ag, Ag2O; P: BiPO4; BWO: Bi2WO6) were synthesized for effectively purification of antibiotics and bacteria contaminated wastewater. GO added in synthesis of BWO (1st-hydrothermal) and induced of Ag dopants (2nd-hydrothermal) of GO–Ag/P/BWO were fabricated separately and marked as GO(I)–Ag/P/BWO and GO(II)–Ag/P/BWO, characterized by different tests (FT-IR, XRD, Raman, XPS, SEM, TEM, TG, UV-VIS, PL, photocurrent density, and EIS). To testify the visible light driven photocatalytic activity of the fabricated photocatalysts, Rhodamine B (Rh B) and amoxicillin (AMX) was chosen as model emerging organic contaminants and antibiotics, respectively. While gram-negative strain Escherichia coli (E. coli) was selected as model waterborne bacteria. The results showed that GO(II)–Ag/P/BWO photocatalyst was synthesized successfully, and possessed high crystallinity, low generated electron-hole recombination rate, and high photocurrent density. The system can produce energetic active species (h+, O2− and OH), exhibiting a superior performance towards removal of Rh B, AMX and E. coli under visible light irradiation. Comparing to other reported GO modified Bi based photocatalyst, GO(II)–Ag/P/BWO had stronger photocatalytic performance in degradation of Rh B, AMX and E. coli, which indicated its high prospects for practical application in environmental wastewater treatment.

An outbreak of Ralstonia insidiosa bloodstream infections caused by contaminated heparinized syringes

IntroductionRalstonia insidiosa, a gram-negative waterborne bacteria able to survive and grow in any type of water source, can cause nosocomial infections, and are considered emerging pathogens of infectious diseases in hospital settings. In this study, we report an outbreak of R. insidiosa at our center related to contaminated heparinized syringes. Material and methodsThe present study was conducted in a tertiary care university hospital in Turkey. An outbreak analysis was performed between September 2021 and December 2021. Microbiological samples were obtained from environmental sources and from patient blood cultures. Species identification was performed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). To investigate the clonality of strains, all confirmed isolates were sent to the National Reference Laboratory and pulsed-field gel electrophoresis (PFGE) was used to perform molecular typing. ResultsSeventeen R. insidiosa isolates were identified from the blood cultures of 13 patients from various wards and intensive care units. Isolates from seven patient blood cultures and two heparinized blood gas syringes were characterized by PFGE. All isolates were found to belong to the same clone of R. insidiosa. ConclusionR. insidiosa was identified as the cause of a nosocomial infection outbreak in our hospital, which was then rapidly controlled by the infection-control team. When rare waterborne microorganisms grow in blood or other body fluid cultures, clinicians and the infection-control team should be made aware of a possible outbreak.

Antibiogram profiles and virulence factors associated with water-borne gram-negative bacteria from Ogbese river, Edo State, Nigeria

Surface waters such as flowing rivers, fresh water lakes and hand dug wells are the major sources of water for most rural dwellers in Nigeria. These are often consumed without testing their potability. This study was conducted to assess the bacteriological quality of surface water sampled from five (5) sampling locations on Ogbese river in Ogbese and Olumoye towns, Ovia North East Local Government Area, Edo State. Water samples were collected in duplicates from the sampling locations during the months of June 2018 to February 2019. Bacteriological analysis of the water samples was conducted using the membrane filtration technique and isolates identified by standard cultural and genomic procedures. Disc diffusion technique was utilized to determine the antibiotic sensitivity profiles of the identified bacteria. Other microbiological analysis which comprised of screening for enterotoxin production, invasiveness, hemolysin production and serum resistance, which are all virulence factors were performed using relevant methods. The total heterotrophic bacterial count varied from 1.0 ± 32.0 ×104𝑐𝑓𝑢/𝑚𝑙 and 1.0 ±0.12 ×104𝑐𝑓𝑢/𝑚𝑙 to 9.7 ± 2.23 ×104𝑐𝑓𝑢/𝑚𝑙. The total coliform count ranged from 0.1 ± 0.02 ×102𝑐𝑓𝑢/𝑚𝑙 to 5.5 ± 0.05 ×102𝑐𝑓𝑢/𝑚𝑙. The observed differences between the mean heterotrophic bacterial and coliform counts recorded for Ogbese and Olumoye sampling points was significant (P< 0.05). The identified bacterial isolates included; Escherichia coli, Enterobacter cloacae, Shigella flexneri, Salmonella enterica, Vibrio cholerae, Klebsiella pneumoniae and Pseudomonas aeruginosa Both E. coli (60.0%) and E. cloacae (60.0%) were the most frequently isolated water borne isolates cultured from Ogbese sampling point. All E. coli and S. enterica isolates exhibited sensitivity towards ciprofloxacin and streptomycin. All S. flexneri isolates were invasive and serum resistant. There is an urgent need by relevant Governmental and Non –Governmental agencies to conduct advocacy programs targeted at these communities on the necessity of treating and disinfecting abstracted water sourced directly from the water body prior to drinking.

Inactivation of biohazards in healthcare wastewater by E-Beam and Gamma irradiation: a comparative study.

The main objective of this study is to evaluate the effect of irradiation by Gamma rays and Electron Beam (E-Beam) on naturally occurring microorganisms shed in healthcare wastewater issued from multi-specialties hospital. We examined the susceptibility of naturally occurring total indicator bacteriophages towards Gamma rays and E-Beam irradiation to evaluate their appropriateness as viral indicators for healthcare wastewater quality control. Results showed that healthcare wastewater is a rich matrix containing bacteriophages surrogates of pathogenic waterborne viruses (4.5 Log10 PFU/100mL for SOMCPH and 2.3 Log10 PFU/100mL for FRNAPH), antibiotic resistant bacteria (Mean concentrations from 2.3 to 5.5 Log10 CFU/100mL), molds and yeasts (2.7 Log10 CFU/100mL), and spores of Clostridium perfringens (Mean concentration of 3.3 Log10 CFU/100mL). After E-Beam irradiation, naturally occurring bacteria in healthcare wastewater showed lower resistance patterns (D10 values ranging between 0.21 ± 0.005 and 0.59 ± 0.005) compared to those obtained after Gamma irradiation (D10 values ranging between 0.25 ± 0.015 and 0.70 ± 0.0001). Spores of Clostridium perfringens were the most resistant assayed microbes either after E-Beam (D10 values of 3.74 ± 0.005) or Gamma irradiation (D10 values of 4.77 ± 0.025) of collected samples. According to inactivation patterns, a dose of 10kGy was sufficient for a complete inactivation of spores. Bacteriophages isolated from healthcare wastewater showed the same resistance patterns as those previously obtained in urban treated sewage and were inactivated using higher doses than waterborne bacteria (D10 values of SOMCPH 1.46 ± 0.057; D10 values of FRNAPH 1.03 ± 0.057). Their resistance to irradiation treatment in such complex matrix corroborates their use to survey the viral quality of healthcare wastewater before their discharge in the urban sanitation network. D10 value analysis showed that bacteria and bacteriophages inactivation by E-Beam irradiation required lower doses than those required for their inactivation using Gamma rays. According to inactivation patterns, a dose of 7kGy was sufficient for total inactivation of both pathogenic bacteria and viruses. Thus, E-Beam irradiation seems to be an efficient physical pre-treatment process for healthcare wastewater treatment prior to its discharge in urban sanitation system to ensure compliance with environmental standards and protect public health.

Capsaicin Potently Blocks Salmonella typhimurium Invasion of Vero Cells.

Salmonella typhimurium (S. typhimurium) is one of the major food and waterborne bacteria that causes several health outbreaks in the world. Although there are few antibiotics against this bacterium, some of these drugs are challenged with resistance and toxicity. To mitigate this challenge, our group explored the ethnomedicinal/herbalism knowledge about a certain spice used in Northern Ghana in West Africa against bacterial and viral infection. This plant is Capsicum chinense (C. chinense). The plant is one of the commonest food spices consumed across the world. The seed of the plant contains both capsaicin and dihydrocapsaicin. Apart from capsaicin and dihydrocapsaicin, other major capsaicinoids in C. chinense include nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. In this pilot work, we investigated the antibacterial activity of pure capsaicin and capsaicin extract obtained from C. chinense against S. typhimurium in vitro. Capsaicin extract showed potent inhibition of S. typhimurium growth at concentrations as low as 100 ng/mL, whereas pure capsaicin comparatively showed poorer inhibition of bacteria growth at such a concentration. Interestingly, both capsaicin extract and pure capsaicin were found to potently block a S. typhimurium invasion of the Vero cell in vitro. Taken together, we believed that capsaicin might work synergistically with dihydrocapsaicin or the other capsaicinoids to inhibit S. typhimurium growth, whereas individually, capsaicin or dihydrocapsaicin could potently block the bacteria entry and invasion of Vero cells.

Statewide Quantitative Microbial Risk Assessment for Waterborne Viruses, Bacteria, and Protozoa in Public Water Supply Wells in Minnesota

Infection risk from waterborne pathogens can be estimated via quantitative microbial risk assessment (QMRA) and forms an important consideration in the management of public groundwater systems. However, few groundwater QMRAs use site-specific hazard identification and exposure assessment, so prevailing risks in these systems remain poorly defined. We estimated the infection risk for 9 waterborne pathogens based on a 2-year pathogen occurrence study in which 964 water samples were collected from 145 public wells throughout Minnesota, USA. Annual risk across all nine pathogens combined was 3.3 × 10–1 (95% CI: 2.3 × 10–1 to 4.2 × 10–1), 3.9 × 10–2 (2.3 × 10–2 to 5.4 × 10–2), and 1.2 × 10–1 (2.6 × 10–2 to 2.7 × 10–1) infections person–1 year–1 for noncommunity, nondisinfecting community, and disinfecting community wells, respectively. Risk estimates exceeded the U.S. benchmark of 10–4 infections person–1 year–1 in 59% of well-years, indicating that the risk was widespread. While the annual risk for all pathogens combined was relatively high, the average daily doses for individual pathogens were low, indicating that significant risk results from sporadic pathogen exposure. Cryptosporidium dominated annual risk, so improved identification of wells susceptible to Cryptosporidium contamination may be important for risk mitigation.

Bacteria isolated from Niger River water in Bamako showed multi-resistance to antibiotics

In Bamako; infectious diseases caused by antibiotic resistant bacteria are major public health problem. Because of the ability of these bacteria to resist to one or more antibiotics, these diseases have been more difficult to treat. Because of antibiotic contamination derived from human activities, rivers become the reservoir for the dissemination of antibiotic resistant bacteria. The use of water containing antibiotic resistant bacteria increased the health risks associated with the waterborne bacteria in animals and humans. The aim of this study is to investigate the presence of antibiotic resistant bacteria from the Niger river water in Bamako rivers. A total of 177 pathogenic bacterial strains were isolated. Among the 177 bacterial isolates, thirty-one (31) were isolated as Staphylococcus aureus, sixty-four (64) were isolated as Salmonella sp. and eighty-two (82) as Escherichia coli. The results from this study showed that the Niger river in Bamako is exposed to high level of antibiotics compound which may lead the bacteria to develop mechanism of antibiotic resistant. This may be behind serious threats to the public health and environment.

Overview of Salmonella Genomic Island 1-Related Elements Among Gamma-Proteobacteria Reveals Their Wide Distribution Among Environmental Species.

The aim of this study was to perform an in silico analysis of the available whole-genome sequencing data to detect syntenic genomic islands (GIs) having homology to Salmonella genomic island 1 (SGI1), analyze the genetic variations of their backbone, and determine their relatedness. Eighty-nine non-redundant SGI1-related elements (SGI1-REs) were identified among gamma-proteobacteria. With the inclusion of the thirty-seven backbones characterized to date, seven clusters were identified based on integrase homology: SGI1, PGI1, PGI2, AGI1 clusters, and clusters 5, 6, and 7 composed of GIs mainly harbored by waterborne or marine bacteria, such as Vibrio, Shewanella, Halomonas, Idiomarina, Marinobacter, and Pseudohongiella. The integrase genes and the backbones of SGI1-REs from clusters 6 and 7, and from PGI1, PGI2, and AGI1 clusters differed significantly from those of the SGI1 cluster, suggesting a different ancestor. All backbones consisted of two parts: the part from attL to the origin of transfer (oriT) harbored the DNA recombination, transfer, and mobilization genes, and the part from oriT to attR differed among the clusters. The diversity of SGI1-REs resulted from the recombination events between GIs of the same or other families. The oriT appeared to be a high recombination site. The multi-drug resistant (MDR) region was located upstream of the resolvase gene. However, most SGI1-REs in Vibrio, Shewanella, and marine bacteria did not harbor any MDR region. These strains could constitute a reservoir of SGI1-REs that could be potential ancestors of SGI1-REs encountered in pathogenic bacteria. Furthermore, four SGI1-REs did not harbor a resolvase gene and therefore could not acquire an integron. The presence of mobilization genes and AcaCD binding sites indicated that their conjugative transfer could occur with helper plasmids. The plasticity of SGI1-REs contributes to bacterial adaptation and evolution. We propose a more relevant classification to categorize SGI1-REs into different clusters based on their integrase gene similarity.

Catalyst-Free Periodate Activation by Solar Irradiation for Bacterial Disinfection: Performance and Mechanisms.

Periodate (PI)-based advanced oxidation process has recently attracted great attention in the water treatment processes. In this study, solar irradiation was used for PI activation to disinfect waterborne bacteria. The PI/solar irradiation system could inactivate Escherichia coli below the limit of detection (LOD, 10 CFU mL-1) with initial concentrations of 1 × 106, 1 × 107, and 1 × 108 CFU mL-1 within 20, 40, and 100 min, respectively. •O2- and •OH radicals contributed to the bacterial disinfection. These reactive radicals could attack and penetrate the cell membrane, thereby increasing the amount of intracellular reactive oxygen species and destroying the intracellular defense system. The damage of the cell membrane caused the leakage of intracellular K+ and DNA (that could be eventually degraded). Excellent bacterial disinfection performance in PI/solar irradiation systems was achieved in a wide range of solution pH (3-9), with coexisting humic acid (0.1-10 mg L-1) and broad solution ionic strengths (15-600 mM). The PI/solar irradiation system could also efficiently inactivate Gram-positive Bacillus subtilis. Moreover, PI activated by natural sunlight irradiation could inactivate 1 × 107 CFU mL-1 viable E. coli below the LOD in the river and sea waters with a working volume of 1 L in 40 and 50 min, respectively. Clearly, the PI/solar system could be potentially applied to disinfect bacteria in water.

Point-of-use photocatalytic device for water disinfection under visible light using ZnO/Gypsum@alginate beads

A working prototype for point-of-use device for water disinfection under visible light using reusable photocatalytic beads is demonstrated. The device could disinfect antibiotic resistant Salmonella enterica serovar in water within 120 min under visible light using 3.0 g/L of ZnO/G@alginate beads·H2O2, •OH and O2•− are envisaged as the notable reactive oxygen species which promoted irreversible impairment of bacterial cell membrane. Treated water had no noticeable impact on gut health of administered animal suggesting the bio-safety of the process. Without any notable decline in performance, ZnO/G@alginate beads are used for 9 consecutive cycles. Prototype is further validated by disinfection of other water borne bacteria viz. Staphylococcus aureus, Escherichia coli and Shigella flexneri and is effective in disinfection of fecal coliform in raw surface water samples. Proposed device may find its use as an off-grid water disinfection system appropriate for most pregnable rural populations and individuals living in remote localities.

Surface plasmon resonance biosensor based on graphene layer for the detection of waterborne bacteria.

As a result of the risks that waterborne bacteria bring to the human body, identifying them in drinking water has become a global concern. In this article, a highly sensitive surface plasmon resonance (SPR) biosensor consisting of prism, Ag, graphene, affinity layer and sensing medium is proposed for rapid detection of the waterborne bacteria. Four SPR-based sensors are first studied with the structures prism/Ag/sensing medium, prism/Ag/affinity layer/sensing medium, prism/Ag/graphene/sensing medium, and prism/Ag/graphene/affinity layer/sensing medium. The latter structure is found to have the highest sensitivity so it is considered for further investigations. Four different commonly used prisms are then demonstrated which are N-FK51A, 2S2G, SF10 and BK7. The structure with the prism N-FK51A is found to correspond to the highest sensitivity so it is considered for further investigations. The structure parameters are then optimized. The proposed SPR sensor can achieve high sensitivity of about 221.63 °/RIU for Escherichia coli and 178.12 °/RIU for Vibrio cholera bacteria with an average value of 199.87 °/RIU. We believe that the proposed structure will open a new window in the field of microorganism detections.

Intensified inactivation of model and environmental bacteria by an atmospheric-pressure air-liquid discharge plasma compared with chlorination

Water-borne pathogenic bacteria are always the top priority to be removed through disinfection process in water treatment due to their threat to human health. It was necessary to develop novel disinfection methods since the conventional chlorine disinfection was inefficient in inactivating chlorine-resistant bacteria, inducing the viable but non-culturable (VBNC) bacteria and forming disinfection by-products (DBPs). In this study, the inactivation of four model strains including Gram-negative (G−), Gram-positive (G+) and environmental samples by atmospheric-pressure air-liquid discharge plasma (ALDP) was assessed systematically. The results showed that ALDP was superior in inactivating all of the samples compared with chlorination. During 10 min ALDP treatment, the G− bacteria were completely inactivated, and the G+ one was inactivated by more than 4.61 logs. The inactivation of bacteria from a campus lake and a wastewater treatment plant effluent exceeded 99.82% and 97.78%, respectively. For G− bacteria, ALDP resulted in a much lower (102∼103 times) levels of VBNC cells than chlorination. ALDP could effectively remove the chlorine-resistant bacteria. More than 96.41% of the intracellular DNA and 99.99% of the extracellular DNA were removed, whereas it was only 56.35% and 12.82% for chlorination. ALDP had a stronger ability to destroy cell structure than chlorination, presumably due to the existence of ROS (·OH, 1O2 and O2−). GC-MS analysis showed that ALDP produced less DBPs than chlorination. These findings provided new insights for the application of discharge plasma in water disinfection, which could be complemental or alternative to the conventional disinfection methods.

Disinfection profiles and mechanisms of E. coli, S. aureus, and B. subtilis in UV365/chlorine process: Inactivation, reactivation, and DBP formation

UV/chlorine is an emerging process that can simultaneously control waterborne bacteria and disinfection byproducts (DBPs). In this study, performance of UV365/chlorine process on bacterial inactivation was comprehensively investigated, which showed better performance than UV365 alone and chlorine alone processes. The better performance could be attributed to the reactive species (especially O3 and HO) generated in UV365/chlorine process. Inactivation of E. coli, S. aureus, and B. subtilis was further reflected via the evaluation of membrane permeability, leakage of adenosine-triphosphate (ATP), and damage of cell surface morphology. The results also demonstrated that bacterial inactivation generally follow the order of E. coli, S. aureus, B. subtilis. To ensure the disinfection efficiency, reactivation of three bacteria after complete treatment by UV365 alone, chlorine alone and UV365/chlorine processes was evaluated, and the combined process showed the lowest reactivation potential. Further, formation of disinfection byproducts (DBPs) from the bacterial suspensions with/without UV365/chlorine pretreatment was determined. Bacterial suspensions treated with UV365/chlorine process generated fewer DBPs than that in direct chlorination. Overall, our present study could provide much useful information on the actual application of UV365/chlorine process in drinking water treatment plants.

Sensitivity enhancement of an optical sensor based on a binary photonic crystal for the detection of Escherichia coli by controlling the central wavelength and the angle of incidence

A one-dimensional binary photonic crystal with the structure air/(GaAs,SiO2)N/D/(GaAs,SiO2)N/glass is proposed as an optical sensor to detect E. coli bacteria, where D is the defect layer. Water and E. coli bacteria are treated as the defect layer. The sensing mechanism of the proposed detector is based on the refractive index difference between pure water and waterborne bacteria samples. The transmission spectra of the photonic crystal are investigated and the sensitivity to E. coli bacteria is calculated. The effects of the central wavelength and the angle of incidence on the sensitivity and sensor performance parameters are studied. It is found that the central wavelength increase can enhance the sensor sensitivity and most of the performance parameters. Increasing the incidence angle can improve the sensitivity and all the performance parameters such as full width at half maximum, quality factor, detection limit, sensor resolution, signal-to-noise ratio, dynamic range, detection accuracy and figure of merit. The sensitivity, quality factor and detection limit that have been obtained are 213.259 nm/RIU, 10,010 and 0.0318, respectively.

Electrochemical Detection of Waterborne Bacteria Using Bi-Functional Magnetic Nanoparticle Conjugates.

Detection of microbial contamination in water is imperative to ensure water quality. We have developed an electrochemical method for the detection of E. coli using bi-functional magnetic nanoparticle (MNP) conjugates. The bi-functional MNP conjugates were prepared by terminal-specific conjugation of anti-E. coli IgG antibody and the electroactive marker ferrocene. The bi-functional MNP conjugate possesses both E. coli-specific binding and electroactive properties, which were studied in detail. The conjugation efficiency of ferrocene and IgG antibodies with amine-functionalized MNPs was investigated. Square-wave voltammetry enabled the detection of E. coli concentrations ranging from 101–107 cells/mL in a dose-dependent manner, as ferrocene-specific current signals were inversely dependent on E. coli concentrations, completely suppressed at concentrations higher than 107 cells/mL. The developed electrochemical method is highly sensitive (10 cells/mL) and, coupled to magnetic separation, provides specific signals within 1h. Overall, the bi-functional conjugates serve as ideal candidates for electrochemical detection of waterborne bacteria. This approach can be applied for the detection of other bacteria and viruses.

Design of a novel optical sensor for the detection of waterborne bacteria based on a photonic crystal with an ultra-high sensitivity

Today, detecting processes of waterborne bacteria in drinking water is a global challenge because these bacteria can lead to dangerous diseases to the human body. In this paper, we have developed a new sensor for the detection of waterborne bacteria based on a one-dimensional defective binary photonic crystal. The defect layer is taken as a water sample located in the middle of the photonic crystal structure. A resonant peak is then created within the photonic bandgap. The sensing mechanism of the proposed detector is based on the refractive index difference between pure water and waterborne bacteria samples. This index change leads to a shift in the resonant peak position in the transmission spectrum. The effects of many parameters, such as incident angle, defect layer thickness, thicknesses of periodic layers and the number of periods on the sensitivity are investigated. At the optimum conditions, the proposed sensor exhibits a sensitivity of 3639.53 nm/RIU which is ultra-high compared with recently published biosensor papers. It also showed a high-quality factor (7521.26), high figure of merit (8977.98 RIU−1) and low detection limit (1.77 × 10−5 RIU). The proposed design could distinguish between the different types of waterborne bacteria although the minute difference between their refractive indices. In addition to that, it has a simple design so that it can be easily fabricated.

Application of Hydrogen Peroxide to Improve the Microbiological Stability of Food Ice Produced in Industrial Facilities

This work was aimed to produce an “active” food ice to preserve its microbiological safety over time. With this in mind, ice cubes were processed with the addition of H2O2 to water before freezing. Four food ice productions were performed at the industrial level: one control trial without the addition of H2O2 (0OX) and three experimental trials obtained by adding 4, 8, and 12 mg/L of H2O2 (4OX, 8OX, and 12OX), respectively. After production, all food ice trials were artificially contaminated with 102 CFU/100 mL of water-borne pathogenic bacteria (Escherichia coli ATCC 25922, Enteroccus faecalis ATCC 29212, and Pseudomonas aeruginosa ATCC 27853) inoculated individually. Thawed ice samples were then subjected to microbiological analyses performed by the membrane filtration method and the results indicated that only trial 12OX was able to inactivate all bacteria strains. In conclusion, the addition of 12 mg/L H2O2 represents an optimal cost-effective strategy to preserve the microbiological stability of food ice even when it is improperly handled after production.

Theoretical study of one-dimensional defect photonic crystal as a high-performance sensor for water-borne bacteria

Theoretical study of one-dimensional defect photonic crystal as a high-performance sensor for water-borne bacteria