Antibacterial Filter Research Articles

Correlation between the Antibacterial Ability of Silver Nanoparticle Coated Air Filters and the Dust Loading

This study investigated the correlation between the antibacterial ability of silver nanoparticle air filters with the related dust loading. In addition, a decay equation with which the life cycle of the antibacterial air filters could be predicted was developed. Samples of a HEPA (High Efficiency Particulate Air) filter were coated with an antibacterial agent, silver nanoparticles, which were synthesized via an atmospheric spark discharge method and deposited onto the filters using forced convection flow. A specific amount of dust particles was then blown onto each filter sample. Two kinds of bacteria, Escherichia coli (E. coli), representing Gram-negative bacteria, and Staphylococcus epidermidis (S. epidermidis), representing Gram-positive bacteria, were used in order to examine the antibacterial abilities of the filter samples. The results of the disc diffusion method showed that the dust loading adversely affected the antibacterial efficacy. However, the silver nanoparticle mass density on a filter with a certain amount of dust does increase the antibacterial ability to a certain extent. Finally, decay equations for the decline rates of the antibacterial ability against E. coli and S. epidermidis were obtained with a dimensionless pressure drop across the antibacterial filter samples.

Correlation between the Antibacterial Ability of Silver Nanoparticle Coated Air Filters and the Dust Loading

This study investigated the correlation between the antibacterial ability of silver nanoparticle air filters with the related dust loading. In addition, a decay equation with which the life cycle of the antibacterial air filters could be predicted was developed. Samples of a HEPA (High Efficiency Particulate Air) filter were coated with an antibacterial agent, silver nanoparticles, which were synthesized via an atmospheric spark discharge method and deposited onto the filters using forced convection flow. A specific amount of dust particles was then blown onto each filter sample. Two kinds of bacteria, Escherichia coli (E. coli), representing Gram-negative bacteria, and Staphylococcus epidermidis (S. epidermidis), representing Gram-positive bacteria, were used in order to examine the antibacterial abilities of the filter samples. The results of the disc diffusion method showed that the dust loading adversely affected the antibacterial efficacy. However, the silver nanoparticle mass density on a filter with a certain amount of dust does increase the antibacterial ability to a certain extent. Finally, decay equations for the decline rates of the antibacterial ability against E. coli and S. epidermidis were obtained with a dimensionless pressure drop across the antibacterial filter samples.

Processing and Characterization of Porous Silica-Ag-Nanoparticle Composites Produced by Pulsed Electric Current Sintering

This paper studies influence of the process temperature and time on the properties of the compacts made of Ag-SiO2 powder by the pulsed electric current sintering (PECS). Silica particles doped with Ag nanoparticles were prepared by modified Stöber method, and calcinated at 573 K in air resulting in average silica particle size of ~1.1 µm and agglomerate size up to 32 µm. There was about 7 wt.% of silver in the structure and the diameter of the silver particles on the silica carriers was 30 ±7 nm on average. The composite powder was sintered into porous compacts by PECS at 873, 973, 1073, or 1173 K for 10, 20, or 30 min under pressure of 50 MPa. Samples were characterized by SEM, XRD, UV-vis-spectrometer, and laser diffraction. During PECS compaction grain growth of silver particles was observed and the measured average size of Ag in 873 K and in 1173 K samples were 65 nm and 170 nm, respectively. The porosity of the materials did not show remarkable change, as the relative density ranged from 76 to 79 %. Thus, it is possible to produce porous silica based materials with controlled Ag-nanoparticle size by PECS. These materials may be optimized for, e.g., different kinds of antibacterial filters.

Chitosan-based nanofibrous membranes for antibacterial filter applications

Nanofibrous membranes have drawn considerable interest for filtration applications due to their ability to withstand high fluid flux while removing micro- and nano-sized particulates from solution. The desire to introduce an antibacterial function into water filter applications presents a challenge to widespread application of fibrous membranes because the addition of chemicals or biocides may produce harmful byproducts downstream. Here, we report the development of chitosan–polycaprolactone (PCL) nanofibrous membranes to utilize the natural antibacterial property of chitosan for antibacterial water filtration. Chitosan–PCL fibers with diameters of 200–400nm and chitosan contents of 25, 50 and 75wt% were prepared by electrospinning. In a series of bacterial challenge tests, chitosan–PCL fibrous membranes significantly reduced Staphylococcus aureus adhesion compared to PCL fibrous membranes. In water permeability and particulate size removal tests, fibrous membranes with 25% chitosan supported the greatest water flux (∼7000L/h/m2) with 100% removal of 300-nm particulates, while maintaining the membrane integrity. This study demonstrates the potential of chitosan–PCL nanofibrous membranes as pre-filters for water filtration systems that demonstrate combinatorial filtration and intrinsic antibacterial advantages.

The TG and zeta-potential characterization of silver-zeolite composites for anti-bacterial capability

The porous, stable zeolite materials impregnated with 1 wt% silver (AgZ) were used as anti-bacterial filters to reduce the bio-aerosols as bacterial counts in the indoor air quality of a medical facility to fulfill the regulation of the Taiwan environmental protection administration. The anti-bacterial efficacies of AgZ reach 99 % after 2 h of air circulation in rooms, and its capacity could be re-generated through heated air at 160 °C. The stability and characteristics of AgZ were analyzed by the transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and zeta-potential. Heat of the endothermic reaction of AgZ was evaluated to be 377–388 J g−1 and was discovered as stable below 300 °C. The analysis results also showed the recovery of second isoelectric points at pH 8.5 of AgZ could represent the ability to adsorb negative charged bio-aerosols as well as anti-bacterial capacity.

Ten Million Fold Reduction of Live Bacteria by Bactericidal Filter Paper

AbstractAn extremely efficient bactericidal filter paper is developed that is capable of removing 99.99999% of Escherichia coli bacteria in a simple filtration process. The novel approach utilizes two active bactericidal components: a bactericidal agent, triclosan, which acts synergistically with a cationic polyelectrolyte binder with antibacterial properties. The biocide is incorporated into the block copolymer micelles attached to the cellulose fibers via the cationic polyelectrolyte. As the water containing the bacteria is passed by gravity through the filter paper, the bactericidal agents are transferred to the bacteria through collisions with the micelles or coated fibers. A synergy between the biocide and the polyelectrolyte is responsible for the extremely high efficiency in deactivating the bacteria. The filtered water is free of biocide other than that transported by the dead bacteria. This technology represents a very simple approach to provide potable water under a wide range of primitive conditions.

MORPHOLOGICAL FEATURES OF BIOFILMS IN POTENTIALLY DANGEROUS WATER SYSTEMS

The specific features of the structural organization of biofilms formed with the participation of Legionella in the water supply systems of health care facilities (HCF) and in the water-cooling towers of industrial enterprises in the Moscow Region were studied to elaborate new approaches to preventing legionellosis in the potentially dangerous water systems. A massive Legionella biofilm in association with other gram-positive and gram-negative bacteria was shown to form for 2-3 weeks on the protective antibacterial filters built in the hot water supply systems of the risk-group units of HCFs. The specific features of the structural organization of biofilms of Legionella onto surface of water-cooling towers, which were a set of a few systematic groups of microorganisms, such as fungi, gram-positive and gram-negative bacteria, and cyanobacteriae located in the presence of a matrix and metal inclusions. The results confirm that it is necessary to destruct and prevent the formation of natural Legionella biofilms in the potentially dangerous water systems, which is an essential component of the current strategy for the prevention of legionellosis.

Potential of a functionalised nanofibre microfiltration membrane as an antibacterial water filter

The aim of this study was to evaluate the use of functionalised electrospun nanofibre microfiltration membranes, spun by an innovative electrospinning technique, for water disinfection. As such, this study bridges between development in electrospinning techniques for the production of flat sheet membranes and the application of these membranes in water filtration and disinfection. Different functionalising agents (nanosilver, bronopol, WSCP, …) were initially evaluated in short term experiments. The most performing agent (WSCP) resulted in a 5.2 log10 colony forming units removal per 100ml (CFU/100ml) hospital wastewater when a 5omf% WSCP functionalised membrane was applied. Long term lab scale tests showed a 5.6 log10 CFU/100ml removal for Staphylococcus aureus and a 4.0 log10 CFU/100ml removal for Escherichia coli, indicating a better removal of Grampositive bacteria. Leaching experiments showed a 10% wash-out of the applied functionalising agent. This leaching did not obstruct the pathogen removal capacity of the functionalised nanofibres. Further research should be conducted towards the reproducibility and controllability of electrospinning of functional nanofibres.

Production of antibacterial filter paper from wood cellulose

Paper has a visible market-share in hygiene products either in the form of personal hygiene or as food packaging. The designation “hygiene”, though it suggests cleanliness, does not imply antibacterial properties; rather it can be stated that hygiene products do not initiate microorganism growth. Antibacterial products could restrict propagation of pathogenic bacteria either by holding bacteria or by trapping and neutralizing them. Most research in this field has been conducted using textile fibers as a substrate, but the present work uses paper instead. The objective was to produce an antibacterial filter paper capable of trapping and neutralizing pathogenic microorganisms using wood fibers. To produce antibacterial paper, chitosan and nanosilver capped with PAA (polyacrylic acid) were deposited on the fiber surface using a layer-by-layer technique. Samples for the tests were prepared from refined bleached softwood (RBSW) kraft pulp. The deposition of antibacterial agents on fiber as well as paper were monitored using a zeta potential analyzer (ZPA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIRS). The minimum requirement for deposition of the agents was a multilayer comprised of eight alternating layers. The deposition onto fiber or paper had no effect on tensile strength or the pore structure of the substrate.

POTENTIAL OF NANOCHITOSAN-COATED INERT SUBSTRATE AS AN ANTIBACTERIAL WATER FILTER

The current study deals with the aspects of surface modification of Polyurethane (PU) foam using chitosan nanoparticles to purify the water from bacteria. The present work also addresses the synthesis and characterizations of chitosan nanoparticles. The particles were characterized by evaluating their topography, size via SEM. These nanoparticles were then coated onto PU foams in order to evaluate these filter samples for purification efficiency through standardized test procedures. The percentage bacterial reduction with the chitosan nanoparticle coated PU foam was 100%, whereas it was only 58.33% with uncoated PU foam. The results were confirmed by flow test which showed coliform count of 30 CFU/mL in the input water, whereas in the Output water the coliform count was 0. Hence, from the overall results it can be confirmed that the PU foams coated with chitosan nanoparticles have good purification efficiency and can be used as an antibacterial water filter.

Study on an Air Filter Material Immobilized with Bio-Antimicrobials

Use of an air filter material combined with antibacterial agents is one of the most effective methods to resolve the problem of air filter contaminated by pathogenic microbes. ε-Polylysine and Natamycin are two biogenic antimicrobials that have been widely applied in recent years because of their high antibacterial efficiency, harmlessness to human body and environmental friendliness. In this paper, a novel antibacterial air filter material was prepared by immobilizing ε-Polylysine and Natamycin onto fiberglass high efficiency air filter media by acrylate adhesive bonding. The mechanical properties, aerosol filtration properties, and antibacterial properties were then evaluated. An improvement in the mechanical properties of the material prepared was seen compared to the untreated filter media. The filtration efficiency of the material prepared for particle aerosols and bioaerosols both greater than 99.997%. Antibacterial efficiency of the material prepared against Staphylococcus aureus and Escherichia coli in suspensions were both greater than 99.99% compared to the untreated filter media. The anti-mildew effect against Aspergillus niger in suspension was strong compared to the untreated filter media. Antibacterial efficiency of the material prepared against bacteria in bioaerosols was greater than 99.99%. Observed with Scanning Electron Microscope, most bacteria on antibacterial filter media appeared to be dead. Thus, antibacterial air filter material prepared by immobilizing bio-antimicrobials on fiberglass had a strong inhibitory effect against gram-positive bacteria, gram-negative bacteria and fungi, with no impairment of the intrinsic properties. This kind of material appears to be promising for application in air cleaning and biological protection fields.

Cluster of Pseudoinfections withBurkholderia cepaciaAssociated with a Contaminated Washer-Disinfector in a Bronchoscopy Unit

In December 2008, bronchoalveolar lavage fluid samples obtained from 3 patients were positive for Burkholderia cepacia complex on culture. Samples obtained from bronchoscopes and rinse-water samples obtained from the washer-disinfector were found to be positive for B. cepacia complex. The cause of this pseudo-outbreak was that the washer-disinfector was installed without the required antibacterial filter.

Fabrication of antibacterial water filter by coating silver nanoparticles on flexible polyurethane foams

In this paper, we fabricated silver-coated polyurethane foams and used it as a bacterial filter for contaminated drinking water. Flexible PU foams were soaked in silver colloidal solutions for 10 h, then washed and air-dried at room temperature. The prepared silver colloidal solutions and silver-coated PU materials were characterized by several techniques including TEM, FESEM/EDS, UV-VIS, ICP-AAS, and Raman spectroscopy. The TEM images showed that the size of silver nanoparticles in colloidal solutions varies from 6 to 12nm. The Raman, FE-SEM/EDS and ICP-AAS data illustrated that silver nanoparticles were stable on the PU foam and were not washed away by water. Furthermore, the microbiological tests (tube tests and flow test) were carried out on silver-coated PU materials with the Coliforms, E. coli, and B. subtilis. The obtained results showed that the bacteria was killed completely with antibacterial efficiency of 100% being observed. Our research suggests that silver-coated polyurethane foams can be used as excellent antibacterial water filters and would have several applications in other sectors.

Bacterial Contamination in Solution Aspirated from Non-Sterile Packaged Fentanyl Ampoules: A Laboratory Study

Iatrogenic meningitis is a rare complication of spinal anaesthesia. It is mandatory to use a technique which minimises the risk of introducing bacteria into the subarachnoid space. Currently available fentanyl ampoules require a careful drawing-up technique, as the outside of the ampoule is not sterile and there is potential to contaminate the contents in the drawing-up process. We designed a pilot laboratory study to determine the extent of bacterial contamination of fentanyl solutions drawn up from non-sterile packaged glass fentanyl ampoules using three different methods: aspirating through a 5 microm filter needle only, aspirating through a 5 microm filter needle after swabbing the neck of the ampoule with isopropyl alcohol and aspirating through an antibacterial filter in addition to the 5 microm filter needle. Ten anaesthetists used each method once, in randomised order to draw up solution from three different fentanyl ampoules. Samples underwent bacterial culture in blood agar and enrichment broth for 48 hours. No significant growth was seen in any sample. This pilot study did not identify any bacterial contamination of fentanyl solution irrespective of which of the three methods for aspiration was used.

FABRICATION OF ANTIBACTERIAL WATER FILTER BY COATING SILVER NANOPARTICLES ON FLEXIBLE POLYURETHANE FOAMS

In this paper, we fabricated silver-coated polyurethane foams and used it as a bacterial filter for contaminated drinking water. Flexible PU foams were soaked in silver colloidal solutions for 10hrs, then washed and air-dried at room temperature. The prepared silver colloidal solutions and silver-coated PU materials were characterized by several techniques including TEM, FE-SEMEDS, UV-Vis, ICP-AAS, and Raman spectroscopy. The TEM images showed that the size of silver nanoparticles in colloidal solutions varies from 6 to 12nm, The Raman, FE-SEM/EDS and ICP-AAS data illustrated that silver nanoparticles were stable on the PU foam and were not washed away by water. Furthermore, the microbiological tests (tube tests and flow test) were carried out on silver-coated PU materials with the Coliforms, E. coli, and B. subtillis. The obtained results showed that the bacteria were killed completely with antibacterial efficiency of 100% being observed. Our research suggests that silver-coated polyurethane foams can be used as excellent good antibacterial water filters and would have several applications in other sectors.

Humidification Performance of 48 Passive Airway Humidifiers: Comparison With Manufacturer Data

Introduction Heat and moisture exchangers (HMEs) are increasingly used in the ICU for gas conditioning during mechanical ventilation. Independent assessments of the humidification performance of HMEs are scarce. The aim of the present study was thus to assess the humidification performance of a large number of adult HMEs. Method We assessed 48 devices using a bench test apparatus that simulated real-life physiologic ventilation conditions. Thirty-two devices were described by the manufacturers as HMEs, and 16 were described as antibacterial filters. The test apparatus provided expiratory gases with an absolute humidity (AH) of 35 mg H2O/L. The AH of inspired gases was measured after steady state using the psychrometric method. We performed three hygrometric measurements for each device, measured their resistance, and compared our results with the manufacturer data. Results Of the 32 HMEs tested, only 37.5% performed well (≥ 30 mg H2O/L), while 25% performed poorly (< 25 mg H2O/L). The mean difference (± SD) between our measurements and the manufacturer data was 3.0 ± 2.7 mg H2O/L for devices described as HMEs (maximum, 8.9 mg H2O/L) [p = 0.0001], while the mean difference for 36% of the HMEs was > 4 mg H2O/L. The mean difference for the antibacterial filters was 0.2 ± 1.4 mg H2O/L. The mean resistance of all the tested devices was 2.17 ± 0.70 cm H2O/L/s. Conclusions Several HMEs performed poorly and should not be used as HMEs. The values determined by independent assessments may be lower than the manufacturer data. Describing a device as an HME does not guarantee that it provides adequate humidification. The performance of HMEs must be verified by independent assessment. Heat and moisture exchangers (HMEs) are increasingly used in the ICU for gas conditioning during mechanical ventilation. Independent assessments of the humidification performance of HMEs are scarce. The aim of the present study was thus to assess the humidification performance of a large number of adult HMEs. We assessed 48 devices using a bench test apparatus that simulated real-life physiologic ventilation conditions. Thirty-two devices were described by the manufacturers as HMEs, and 16 were described as antibacterial filters. The test apparatus provided expiratory gases with an absolute humidity (AH) of 35 mg H2O/L. The AH of inspired gases was measured after steady state using the psychrometric method. We performed three hygrometric measurements for each device, measured their resistance, and compared our results with the manufacturer data. Of the 32 HMEs tested, only 37.5% performed well (≥ 30 mg H2O/L), while 25% performed poorly (< 25 mg H2O/L). The mean difference (± SD) between our measurements and the manufacturer data was 3.0 ± 2.7 mg H2O/L for devices described as HMEs (maximum, 8.9 mg H2O/L) [p = 0.0001], while the mean difference for 36% of the HMEs was > 4 mg H2O/L. The mean difference for the antibacterial filters was 0.2 ± 1.4 mg H2O/L. The mean resistance of all the tested devices was 2.17 ± 0.70 cm H2O/L/s. Several HMEs performed poorly and should not be used as HMEs. The values determined by independent assessments may be lower than the manufacturer data. Describing a device as an HME does not guarantee that it provides adequate humidification. The performance of HMEs must be verified by independent assessment.

Postoperative Prevention of Nosocomial Pneumonias, by Using Airway Filters under Artificial Ventilation

Objective: to determine the duration of exposition of filters and their most optimum position in different types of respiratory circuits. Subjects and methods. Group 1 comprised patients receiving not more than 12-hour artificial ventilation (AV) through a coaxial respiratory-circuit, without a humidifier, moisture accumulators, and a nebulizer. The filters were set between the intubation tube and the circuit. Group 2 included patients having more than 12-hour AV through the disposal respiratory circuits including a nebulizer, a humidifier, and inspiratory and expiratory moisture accumulators. The filters were set in front of the inspiratory circuit and behind the expiratory one on an AV apparatuses. Before regularly replacing a filter and/or a circuit, samples were taken for bacteriological tests from different portions of the circuit at various intervals: 4, 12, 24, 48, 96, 120, and 144 hours after initiation of AV, as well as before tracheal extubation in a patient. Results. The data obtained during the study have indicated that the breathing circuit filters afford a reliable protection from the entry of environmental microorganisms into the patient’s respiratory tract. In Group 1, AV did not result in the occurrence of pneumonia or tracheobronchitis. The moisture accumulators and the Y-shaped connector are the most infection-susceptible parts of a respiratory circuit. Mechanical circuit contamination and a larger number of pathogenic microbial strains were observed after 4—5-day AV. Conclusion. All procedures associated with circuit seal failure should be performed, by observing the aseptic rules. The recommended time of using a respiratory circuit during prolonged AV is 96—120 hours. Key words: intensive care unit, artificial ventilation, nosocomial pneumonia, antibacterial respiratory circuit filter.

Prevention of Nosocomial Respiratory Infections

Objective: to evaluate the efficiency of an extended package of preventive measures on the incidence of nosocomial respiratory infections in surgical patients at an intensive care unit (ICU). Subjects and methods. The study included 809 patients aged 35 to 80 years. A study group comprised 494 patients in whom an extended package of preventive measures was implemented during 7 months (March-September). A control group consisted of 315 patients treated in 2004 in the same period of time (March-September). The groups were stratified by age, gender, underlying diseases, and APACHE-2 and SOFA scores. The extended package of anti-infectious measures involved a high air purification in ICUs («Flow-M» technology), routine use of ventilatory filters, closed aspiration systems with a built-in antibacterial filter under artificial ventilation for over 2 days. Results. The proposed technologies could reduce the frequency of tracheobronchitis and ventilator-associated pneumonias in the groups of patients at high risk for nosocomial infections substantially (by more than twice). Conclusion. The findings have led to the conclusion that the extended package of preventive measures is effective in preventing respiratory infections in ICU patients. Of special note is the proper prevention of upper airway contamination with pathogenic microorganisms, by employing the closed aspiration systems with a built-in antibacterial filter. The routine use of high-tech consumables in the intensive care of surgical patients causes a considerable decrease in the incidence of nosocomial pneumonia, ventilator-associated pneumonia, and purulent tracheobronchitis and a reduction in the number of microbiological studies. Key words: ventilator-associated pneumonia, prevention of nosocomial infections, closed aspiration system.

Postoperative infections after major heart surgery and prevention of ventilator-associated pneumonia: a one-day European prevalence study (ESGNI-008)

Few data have been published on the prevalence of postoperative infection in patients undergoing major heart surgery (MHS). The degree of compliance with standard measures used to prevent them is unknown. This study assessed the prevalence of infections, particularly ventilator-associated pneumonia (VAP), in patients undergoing MHS in 42 institutions from 13 European countries. On the study day, there were 321 postoperative MHS patients, of whom 164 (51%) were mechanically ventilated. The overall prevalence of infection was 26.8%. Lower respiratory tract infections represented 57% of all the infections present on the study day. Other infections included intravenous-catheter-related bloodstream infections (2.8%), surgical site infections (2.2%), urinary tract infections (0.9%) and postoperative mediastinitis (0.9%). Of the mechanically ventilated patients, 55 (33.5%) were not being nursed in a semi-recumbent position, 36 (22%) had heat-moisture exchangers with no antibacterial filters, and intracuff pressure was not monitored in 78 patients (47.6%). Only 13 patients (8%) were given continuous subglottic suctioning, 64 patients (39%) did not receive postural oscillation, and gastric overdistension was not actively prevented in 23 patients (14%). In conclusion, these data from intensive care units across Europe provide information on postoperative infections in an important subset of the patient population, and stress the need for active interventions to prevent VAP in patients undergoing MHS.

Potential of silver nanoparticle‐coated polyurethane foam as an antibacterial water filter

Silver nanoparticles can be coated on common polyurethane (PU) foams by overnight exposure of the foams to nanoparticle solutions. Repeated washing and air-drying yields uniformly coated PU foam, which can be used as a drinking water filter where bacterial contamination of the surface water is a health risk. Nanoparticles are stable on the foam and are not washed away by water. Morphology of the foam was retained after coating. The nanoparticle binding is due to its interaction with the nitrogen atom of the PU. Online tests were conducted with a prototypical water filter. At a flow rate of 0.5 L/min, in which contact time was of the order of a second, the output count of Escherichia coli was nil when the input water had a bacterial load of 10(5) colony-forming units (CFU) per mL. Combined with the low cost and effectiveness in its applications, the technology may have large implications to developing countries.