Disinfection Ability Research Articles

Highly efficient g-C3N4/TiO2/kaolinite composite with novel three-dimensional structure and enhanced visible light responding ability towards ciprofloxacin and S. aureus

A novel 3D heterogeneous g-C3N4/TiO2/kaolinite composite with enhanced visible light activity was fabricated via a mild sol-gel method associated with chemical stripping and self-assembly. Compared with bare photocatalysts, the g-C3N4/TiO2/kaolinite 3D structure exhibits enhanced adsorption-photocatalytic degradation ability for the removal of ciprofloxacin (CIP) under visible-light irradiation, and also facilitate the recyclability of the photocatalyst as demonstrated from the reusability test. The apparent rate constant of the composite is up to around 5.35 times, 6.35 times and 4.49 times that of bare TiO2, g-C3N4 and P25, respectively, and a possible degradation pathway was also proposed. On the other hand, the as-received composite also exhibited enriched disinfection ability towards S. aureus. It is indicated that the superoxide radical (O2−) is the main active species in the degradation process, and the superior photocatalytic performance of composite should be mainly attributed to both the improvement of light harvesting as well as the enhanced separation and transfer efficiency. It is expected that this novel ternary visible-light responding composite would be a promising candidate material for the organic pollutants degradation and bacteria inactivation.

Evaluation of disinfectants and antiseptics to eliminate bacteria from the surface of turkey eggs and hatch gnotobiotic poults

Bird eggs are in contact with intestinal microbiota at or after oviposition, but are protected from bacterial translocation by a glycoprotein cuticle layer, the shell, and internal membranes. In a preliminary study, turkey eggs were hatched in a germ-free environment. Firmicutes 16S rRNA gene was detected in the cecal microbiota of hatched poults, suggesting that poults may acquire spore-formers by exposure to shell contents during hatching. Generating gnotobiotic poults for research requires elimination of bacteria from the egg’s surface without damaging the developing embryo. The ability of different disinfectants and antiseptics to eliminate eggshell bacteria without harming the developing embryo was tested. Different classes of disinfectants and antiseptics (halogens, biguanidines, and oxidants) were selected to target spores and vegetative bacteria likely present on the egg’s surface. Eggs were treated by fully immersing in heated antiseptic (betadine or chlorhexidine) or disinfectant (alkaline bleach, acidified bleach, chlorine dioxide, Oxysept-333, or Virkon S) solutions for up to 15 minutes. Shells were aseptically harvested for aerobic and anaerobic culturing of bacteria. Toxicity to the developing embryo was assessed by gross evaluation of developmental changes in treated eggs incubated up to 27 d of embryonation. Halogen disinfectants acidified bleach and chlorine dioxide, and oxidants Oxysept-333 and Virkon-S eliminated viable bacteria from eggshells. However, addition of oxidants, alone or in combination with other treatments, produced significant (P < 0.05) embryotoxicity. The combination treatment of acidified bleach, chlorine dioxide, and betadine produced minimal embryotoxicity and eliminated viable bacteria from whole turkey eggs, and produced hatched poults in a gnotobiotic isolator. As a control, eggs were treated with PBS, incubated, and hatched under germ-replete conditions. After hatching, poults were euthanized and treated poults had no detectable bacterial growth or 16S rRNA gene qPCR amplification, demonstrating that acidified sodium hypochlorite, chlorine dioxide, and betadine safely hatched gnotobiotic poults. Generation of germ-free poults is an important tool and will be used to evaluate the host-pathogen interaction by foodborne pathogens such as Campylobacter spp.

Inactivation of Pseudomonas aeruginosa biofilm after ultraviolet light-emitting diode treatment: a comparative study between ultraviolet C and ultraviolet B.

The objective of this study was to test the inactivation efficiency of two different light-based treatments, namely ultraviolet B (UVB) and ultraviolet C (UVC) irradiation, on Pseudomonas aeruginosa biofilms at different growth stages (24, 48, and 72 h grown). In our experiments, a type of AlGaN light-emitting diodes (LEDs) was used to deliver UV irradiation on the biofilms. The effectiveness of the UVB at 296 nm and UVC at 266 nm irradiations was quantified by counting colony-forming units. The survival of less mature biofilms (24 h grown) was studied as a function of UV-radiant exposure. All treatments were performed on three different biological replicates to test reproducibility. It was shown that UVB irradiation was significantly more effective than UVC irradiation in inactivating P. aeruginosa biofilms. UVC irradiation induced insignificant inactivation on mature biofilms. The fact that the UVB at 296 nm exists in daylight and has such disinfection ability on biofilms provides perspectives for the treatment of infectious diseases.

Care System Versus Transmitted Light Wavefront Pattern of Contact Lenses.

This article compares the optical performance of soft contact lenses (CLs) treated with multipurpose or hydrogen peroxide care systems. The investigated care systems were (1) 3% hydrogen peroxide solution Oxysept (Abbot Medical Optics, Abbott Park, IL) and (2) multipurpose solution Regard (Vita Research, Ariccia, Italy). Three types of silicone hydrogel CLs were studied (comfilcon A, lotrafilcon B, and balafilcon A), unworn and exposed for 30 times to the solutions, which were replaced every 8 hr. The optical performance of the CLs was evaluated through the on-eye transmitted light wavefront patterns by considering new CLs as references. The surface morphology of the CLs was investigated by scanning electron microscopy. Statistically significant modifications in the range 0.1 to 0.3 μm of Zernicke coefficients and modifications of the root mean square of the wavefront aberration function were found for CLs treated with multipurpose solution, in agreement with the observed modifications of the surface morphology. Statistically significant changes were also found after exposure to the hydrogen peroxide solution, but the variation of the Zernicke coefficients was found lower than 0.1 μm, thus being negligible in CL optical performances. In addition to disinfection ability and ocular surface reactions, CL care systems are different in solution-related CL optical performance. Multipurpose solutions may affect the CL surface morphology with significant modifications of the transmitted light wavefront pattern.

Analysis of disinfectant wipe effectiveness – an introductory microbiology lab?

Determining the effectiveness of chemical germicides is a common laboratory exercise used in introductory microbiology course and examines the ability of disinfectants to kill 100% of a test organism. To make this more challenging for students we wanted a more quantitative approach and to make it more interesting we wanted to use commonly available disinfectant wipes. The goal was to develop and test a simple, inexpensive procedure that could be used in an introductory microbiology lab to quantitate the effectiveness of antibacterial wipes. Overnight cultures of S. epidermidis were spotted on glass slides and allowed to dry. Disinfectant wipes were placed over a small rubber stopper and used to “wipe” the slide by rotating 90 degrees with moderate pressure. After wiping the slide 100 µl of sterile water was applied to the slide, and immediately 50 µl was removed and serially diluted to determine the number of bacteria recovered from the slide. Multiple serial dilutions were tried to find a replicable procedure suitable for lab curriculum. Overall, the methods used showed results with rather inconclusive data and the techniques used to date would not be suitable for an introductory microbiology laboratory.

Disinfection of secondary treated sewage using chitosan beads coated with ZnO‐Ag nanoparticles to facilitate reuse of treated water

AbstractBACKGROUNDReuse of treated wastewater is necessary to augment supply of fresh water. Secondary effluent from a sewage treatment plant was disinfected using novel synthesized ZnO–Ag–chitosan beads under visible light.RESULTSFinal most probable number (MPN)/100 mL after 1 h contact time under direct sunlight was 920 with a loading of chitosan, Zn and Ag of 0.4 mg L−1 each. Disinfection resulted from the generation of reactive oxygen species. Disinfection efficiency reduced by 10% and 20%, when the total suspended solids (TSS) concentrations in the sewage were 50 mg L−1 and 100 mg L−1, respectively, compared with that with 30 mg L−1. A 5% and 10% reduction in disinfection efficiency was observed when sulphide concentration in sewage was increased from 10 mg L−1 to 20 mg L−1 and 50 mg L−1, respectively. Disinfection efficiency of the beads decreased by 10% when nitrate concentration in the sewage increased to 30 mg L−1 from zero. These novel beads had residual disinfection ability even after removal of beads from wastewater and these beads were successfully used for disinfection in four consecutive cycles.CONCLUSIONSuccessful disinfection of secondary sewage using chitosan beads coated with ZnO–Ag nanoparticles was established for the first time in this study to facilitate reuse of treated water. © 2017 Society of Chemical Industry

Natural sorbents modified by divalent Cu2+- and Zn2+- ions and their corresponding antimicrobial activity

The objective of this study was to investigate the modification of materials used in wastewater treatment for possible antimicrobial application(s). Granulated activated carbon (GAC) and natural clinoptilolite (CLI) were activated using Cu2+- and Zn2+- ions and the disinfection ability of the resulting materials was tested. Studies of the sorption and desorption kinetics were performed in order to determine and clarify the antimicrobial activity of the metal-activated sorbents. The exact sorption capacities of the selected sorbents, GAC and CLI, activated through use of Cu2+- ions, were 15.90 and 3.60mg/g, respectively, while for the materials activated by Zn2+- ions, the corresponding capacities were 14.00 and 4.72mg/g,. The desorption rates were 2 and 3 orders of magnitude lower than their sorption efficacy for the Cu2+-, and Zn2+-activated sorbents, respectively. The intermediate sorption capacity and low desorption rate indicated that the overall antimicrobial activity of the metal-modified sorbents was a result of metal ions immobilized onto surface sites. The effect of antimicrobial activity of free ions desorbed from the metal-activated surface may thus be disregarded. The antimicrobial activities of Cu/GAC, Zn/GAC, Cu/CLI and Zn/CLI were also tested against Escherichia coli, Staphylococcus aureus, and Candida albicans. After 15min exposure, the highest levels of cell inactivation were obtained through the Cu/CLI and the Cu/GAC against E. coli, 100.0 and 98.24%, respectively. However, for S. aureus and yeast cell inactivation, all Cu2+- and Zn2+-activated sorbents proved to be unsatisfactory. A characterization of the sorbents was performed by X-ray diffraction (XRD), X-ray photo electron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM). A concentration of the adsorbed and released ions was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). The results showed that the antimicrobial performance of the activated sorbents depended on the surface characteristics of the material, which itself designates the distribution and the bioavailability of the activating agent.

Effect of Synthesis Method on the Nanostructure and Solar-Driven Photocatalytic Properties of TiO2-CuS Composites

TiO2 nanospheres were synthesized and then modified with copper(II) sulfide (CuS) to form TiO2-CuS-a and TiO2-CuS-b, respectively, by two different loading methods (direct deposition vs bifunctional linker coupling). The structural, morphological, and optical properties of the two different composites TiO2-CuS-a and TiO2-CuS-b were characterized and compared using FESEM, HRTEM, XRD, XPS, BET, and DRS techniques. The TiO2-CuS-b with a regular “spiky-ball-like” structure exhibited enhanced disinfection ability, improved photodegradation performance of organic pollutants, and hydrogen evolution efficiency under solar and UV light as compared to TiO2-CuS-a (direct deposition method) due to its higher effective combination with CuS through the bifunctional linking molecule, l-cysteine. The influence of CuS content, the structure, and the charge-transfer mechanism were systematically investigated by PL, CV, EIS, and EPR techniques.

Disinfection effect of a continuous-flow ultrasound/ultraviolet baffled reactor at a pilot scale

An ultrasound/ultraviolet (US/UV) baffled reactor was developed to fill the gap in ultraviolet (UV) disinfection associated with disinfection efficiency. According to the previously selected operational condition, a continuous-flow US/UV baffled reactor was continuously operated in a wastewater treatment plant at a pilot scale for nearly three months, and the disinfection influent and effluent were analyzed, including fecal coliforms, Escherichia coli, and fecal streptococci. The US/UV baffled reactor could guarantee a high effluent disinfection performance in terms of fecal coliforms removal even with the fluctuation of the secondary effluent. All the disinfected effluents satisfied the requirement of the “Pollutants Discharge Standard of Municipal Wastewater Treatment Plant in China” (fecal coliforms below 1000CFU/L for class 1A), and 87% of the tested fecal coliforms concentration in the disinfected effluent was below 100CFU/L, nearly eliminating all fecal coliforms. Further analysis of the E. coli and fecal streptococci showed the broad disinfection ability and high disinfection efficiency of the US/UV baffled reactor. The flexibility of the specific energy consumption for the disinfection system depends on the water quality.

Influence of titanium dioxide modification on the antibacterial properties

Abstract Antibacterial properties of 15 titania photocatalysts, mono- and dual-modified with nitrogen and carbon were examined. Amorphous TiO2, supplied by Azoty Group Chemical Factory Police S.A., was used as titania source (Ar-TiO2, C-TiO2, N-TiO2 and N,C-TiO2 calcined at 300°C, 400°C, 500°C, 600°C, 700°C). The disinfection ability was examined against Escherichia coli K12 under irradiation with UV and artificial sunlight and in dark conditions. It has been found the development of new photocatalysts with enhanced interaction ability with microorganisms might be a useful strategy to improve disinfection method conducted under artificial sunlight irradiation. The efficiency of disinfection process conducted under artificial sunlight irradiation with carbon (C-TiO2) and carbon/nitrogen (N,C-TiO2) photocatalysts was similar as obtained under UV irradiation. Furthermore, during dark incubation, any toxicity of the photocatalyst was noted.

The comparison of antimicrobial effectiveness of contact lens solutions

The aim of this study was to compare the effects of widely used multipurpose contact lens solutions against Staphylococcus aureus and Pseudomonas aeruginosa, in addition to cystic and trophozoite forms of Acanthamoeba castellanii and A. polyphaga, that cause microbial keratitis. Three multipurpose solutions were tested: SOLO-care, ReNu, and Opti-Free Express. The test solutions were challenged with P. aeruginosa (ATCC 27853) and S. aureus (ATCC 2913) based on the ISO stand-alone and regiment test procedure for disinfecting products, A. polyphaga (ATCC 30871) and A. castellanii (1501/1A) cystic and trophozoite forms. Multipurpose solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined, and log reductions were calculated. ReNu and SOLO-care resulted in a reduction greater than the required mean 3.0 logarithmic reduction against S. aureus, and SOLO-care and Opti-Free Express resulted in a reduction more than the required mean 3.0 logarithmic reduction against P. aeruginosa. Against the cystic and trophozoite forms of A. castellanii, the log reduction provided by SOLO-care was 1.01 and 1.31 log, respectively. ReNu provided a 0.83 log reduction of the cystic form and a 1.21 log reduction of the trophozoite form. Using Opti-Free Express, the log reduction for both forms was 1.31. SOLO-care led to a 0.61 log reduction of the cystic form of A. polyphaga and a 1.01 log reduction of the trophozoite form. ReNu provided a 0.41 log reduction of the cystic form and a 4.99 log reduction of the trophozoite form. Opti-free Express resulted in a 0.89 log reduction of the cystic form and a 3.11 log reduction of the trophozoite form. Multipurpose contact lens solutions using similar regimens can show different disinfection abilities.

Evaluation of the ability of different detergents and disinfectants to remove and kill organisms in traditional biofilm.

The objective of this study was to assess the ability of different detergent and disinfectant combinations to eradicate bacteria in traditional biofilm. Enterococcus faecalis and Pseudomonas aeruginosa were used to develop biofilm over 8 days. The biofilm on each minimum biofilm eradication concentration peg contained 8 log10 colony forming units (CFU)/cm2 of both bacteria. The detergents evaluated were as follows: Prolystica Enzymatic 2X, Prolystica Neutral 2X, Neodisher, and Endozime Bio-Clean. The disinfectants evaluated were as follows: glutaraldehyde, accelerated hydrogen peroxide, and ortho-phthalaldehyde. Biofilm removal was evaluated using viable count, protein and carbohydrate quantitation, and scanning electron microscopy. Only Prolystica Enzymatic 2X and Endozime Bio-Clean killed both E faecalis (3.90 log10 CFU/mL reduction) and P aeruginosa (3.96 log10 CFU/mL reduction) in suspension. None of the detergents tested could provide >1 log10 CFU/cm2 reduction for bacteria within biofilm. Any combination of detergent and high-level disinfectant reduced the level of both E faecalis and P aeruginosa within biofilm by 3-5 log10 CFU/cm2. Although the combination of Endozime Bio-Clean and glutaraldehyde provided a 6 log10 reduction, it could not eliminate both bacteria within biofilm. Our data indicate that if biofilm accumulates in flexible endoscope channels during repeated rounds of reprocessing, then neither the detergent nor high-level disinfectant will provide the expected level of bacterial removal or killing.

Antibacterial activity and nanocomposite properties of monodispersed silver nanoparticles synthesized by the microwave method

Abstract Monodispersed colloidal silver nanoparticles (Ag-NPs) were synthesized by a simple and rapid microwave method. A precursor, AgNO3, was reduced by ethylene glycol (EG) and N,N-dimethylformamide (DMF) in the presence of polyvinylpyrrolidone (PVP) as a stabilizer or capping agent. It was found that the concentration of AgNO3 significantly affected Ag-NPs particle sizes. The particle sizes decreased when the concentration decreased from 0.1 to 0.05 and 0.01 M, which corresponded to narrow size distribution of the particle diameters of approximately 60 to 80, 30 to 40 and 10 to 20 nm. The spherical-shaped monodispersed Ag-NPs were obtained by using a volume ratio of EG to DMF of 2.75 : 2.25, microwave power of 400 W and heating time of 2 min. The volume ratio of EG to DMF and the microwave power influenced the uniformity of the Ag-NPs shape and size, while the heating time had no effect. For antibacterial application, 60–80 and 10–20 nm Ag-NPs showed good disinfection ability against Escherichia coli (ATCC 25922) at the minimum inhibitory concentrations (MIC) of 32 and 16 µg × ml−1, respectively. In addition, the electrical resistance of the nanocomposites of DMF-loaded Ag-NPs (20–50 nm) without PVP on single-walled carbon nanotubes and polyethylene terephthalate (PET) was measured. As a result, it is obvious that the Ag-NPs help to increase the electrical conductivity of the nanocomposites as the electrical resistance of the Ag-NPs nanocomposites was 4.68 kΩ × cm−2 compared to that of the nanocomposites without Ag-NPs of 8.76 kΩ × cm−2.

A green approach assembled multifunctional Ag/AgBr/TNF membrane for clean water production & disinfection of bacteria through utilizing visible light

In order to realize the ideal water treatment in a green and energy saving manner, TiO2 based multifunctional membrane proved to be a promising approach owing to its capability in utilizing visible light for photocatalytic pollutant degradation and disinfection of bacteria. However, few studies were found about the investigation of antibacterial abilities arising from the intrinsic properties of membrane and its minor composition. Here, a multifunctional membrane was created via a green approach to integrate the merits of hierarchical Ag/AgBr/TNF composites with micro-/-nano porous structures, the intrinsic antibacterial abilities of Ag, and the visible light absorption capability of AgBr. The synergy effects made it being a promising multifunctional membrane for concurrent water filtration and disinfection in a sustainable way. Through a versatile characterization techniques of FESEM, XRD, TES, XPS, and UV-vis spectrometer, the morphology, structure and surface properties of the well prepared Ag/AgBr/TNF multifunctional membrane was thoroughly studied to reveal the deep mechanism behind the high flux, high photocatalytic degradation and disinfection efficiency under visible light. It indicates that the Ag/AgBr/TNF multifunctional membrane exhibited better photocatalytic activity, higher water permeate flux, and higher disinfection abilities over commercial P25 membrane under visible light. Besides the deep mechanism elaborated, the key factors in terms of predominant oxidative species was also exploited in details. This further solidify the broad future of the developed multifunctional membrane. In view of the roaring demand of advanced water treatment and disinfection technology, it is reasonable to believe our developed visible light responsive Ag/AgBr/TNF multifunctional membrane will show great significances to a green and clean future.

Assessment of hardness, microorganism and organic matter removal from seawater by electrocoagulation as a pretreatment of desalination by reverse osmosis

Electrocoagulation (EC) process was used as an alternative pretreatment in order to assess its applicability to replace the conventional pretreatments used to mitigate membrane fouling prior to seawater desalination by reverse osmosis process, such as chemical coagulation, chlorination and scale inhibitors. Electrocoagulation was conducted in a batch cell using aluminum electrodes driven in the galvanostatic mode. Absorbance (UV254nm) and DOC were measured to follow the effectiveness of EC process for removing organic matter from seawater. Likewise, cultivable heterotrophic bacteria were enumerated to assess the disinfection ability of the process and total hardness was monitored. The influence of various operating parameters, namely mixing speed, current density, initial pH and inter-electrode distance, was investigated. The removal of organic matter from seawater by electrocoagulation was improved with higher current density and lower pH. Electrocoagulation removed 70.8% DOC, while absorbance abatement was 89.7% with a complete removal of microorganisms at high current density. Conversely, the abatement of total hardness was weak, about 10%, so that electrocoagulation could not be used as a softening process. Finally, experimental results showed the high potential of electrocoagulation as a pretreatment method to mitigate potential organic fouling and biofouling of reverse osmosis membrane owing to its ability to remove effectively dissolved organic matter and microorganisms from seawater.

Efficacy of dental unit waterlines disinfectants on a polymicrobial biofilm

Due to their high surface-volume ratio, their laminar flow and frequent stagnation periods, dental unit waterlines (DUWL) foster the attachment of microorganisms and the development of biofilm, resulting in the continuous contamination of the outlet water from dental units; this contamination may be responsible for a potential risk of infection due to the exposure of patients and medical staff to droplet inhalation or splashed water. In this study, the anti-biofilm activity of three disinfectants recommended by dental unit manufacturers –Calbenium©, Oxygenal 6© and Sterispray© – was evaluated. A dynamic model simulating DUWL conditions was developed and polymicrobial biofilms containing bacteria (Pseudomonas aeruginosa), fungi (Candida albicans) and Free Living Amoeba (FLA: Vermamoeba vermiformis) were allowed to form. The ability of disinfectants to reduce biofilm formation or to eradicate an already formed biofilm was evaluated. Results showed the various effects of the tested disinfectants according to their composition, concentration and the targeted species. V. vermiformis was resistant to disinfectants, regardless of the tested concentrations and the concentrations recommended by manufacturers were not the most appropriate. Results also showed that Calbenium© was the most effective disinfectant to reduce already formed biofilms; its maximum efficiency was observed from 0.5% on both P. aeruginosa and C. albicans compared to 2 and 3% respectively for Sterispray©. The maximum efficiency of Oxygenal© was observed from 3% on P. aeruginosa but Oxygenal© was unable to totally eliminate C. albicans in the tested conditions, contrary to other disinfectants. Calbenium© was able to prevent biofilm formation efficiently even if it displayed no prophylactic activity against V. vermiformis. Overall, the FLA survival may contribute to maintaining other species. Finally the tested disinfectants were partially active against sessile microorganisms and more suitable concentrations could be used to increase their efficacy. Their use in a prophylactic rather than curative way should be recommended.

Antibacterial Activity of Diode Laser and Sodium Hypochlorite in Enterococcus Faecalis-Contaminated Root Canals.

Introduction:The aim of the present in vitro study was to evaluate the disinfection ability of 980-nm diode laser in comparison with sodium hypochlorite (NaOCl) as a common root canal irrigant in canals infected with Enterococcus faecalis (E. faecalis). Methods and Materials:The root canals of 18 extracted single-rooted premolars were prepared by rotary system. After decoronation, the roots were autoclaved. One specimen was chosen for the negative control, and the remaining teeth were incubated with E. faecalis suspension for two weeks. Subsequently, one specimen was selected as the positive control and the remaining samples were divided into two groups (n=8). The samples of the first group were irrigated with 5.25% NaOCl and the second group were treated with a 980-nm diode laser. Microbial samples were taken from the root canals and bacterial cultivation was carried out. The average value and the standard deviation of colony-forming units (CFU) of each specimen were measured using descriptive statistics. The student’s t-test was used to compare the reduction in CFU in each group. The equality of variance of CFU was measured by the Levene’s test. Results:NaOCl resulted in 99.87% removal of the bacteria and showed significantly more antibacterial effect compared to the 980-nm diode laser which led to 96.56% bacterial reduction (P<0.05). Conclusion:Although 5.25% NaOCl seems to reduce E. faecalis more effectively, the diode laser also reduced the bacterial count. Therefore a 980-nm diode laser could be considered as a complementary disinfection method in root canal treatment.

Antimicrobial and structural effects of different irrigation solutions on gutta-percha cones.

To evaluate the alterations on the surface of gutta-percha cones (GPCs) on exposure to the different irrigation solutions and their possible antibacterial effect against Enterococcus faecalis. (E. faecalis). Disinfection ability of different solutions (5.25% sodium hypochlorite, 2% chlorhexidine, 1% peracetic acid, and QMix) were tested with 96 GPCs and the time of exposure to each solution was 5 and 10 minutes, respectively. GPCs used in this study were contaminated with E.faecalis. After disinfection, GPCs were placed in tubes containing the medium and incubated at 37˚C for 7 days. All tubes were visually checked for turbidity at 24-hour intervals. About 92 new GPCs were analyzed by means of SEM/EDS to assess the topography and chemical elements present on their surface. The data generated was analyzed using Pearson chi-square test, p<0.05. There were no significant statistical differences in disinfection quality between the irrigation solutions used on GPCs contaminated with E. faecalis (p>0.05). SEM/EDS analyses showed no alteration in the superficial features of GPCs after treating with various irrigation solutions. QMix was found to be an effective agent for rapid disinfection of GPCs as well-known irrigation solutions. Irrigation solutions were found to have sterilized the GPCs after both 5 and 10 minutes of exposure.

Heated scallop-shell powder treatment for deactivation and removal of Listeria sp. biofilm formed at a low temperature.

The ability of heated scallop-shell powder (HSSP) to work against Listeria sp. biofilm formed at a low temperature was investigated. A biofilm of L. innocua ATCC 33090 was grown on a glass plate at 15˚C for 15 days, then immersed in HSSP slurry. Following treatment, the disinfection ability of the HSSP against the biofilm was non-destructively quantified by conductimetric assay. The biofilm grown at 15˚C was less sensitive than that grown at 37˚C to HSSP treatment and alkaline treatment. The biofilm grown at 15˚C was completely deactivated by 30 min of HSSP treatment (10 mg/mL, pH 12.5). In contrast, after 30 min treatment with alkaline solution at pH 12.5 or sodium hypochlorite (100 ppm), the activity was reduced by only one order of magnitude. The disinfection efficacy of HSSP (10 mg/mL) against L. innocua is similar to or higher than that of sodium hypochlorite (200 ppm). Fluorescence microscopy validated the results of the conductimetric assay. Therefore, HSSP treatment is a potentially powerful alternative control agent against Listeria sp. biofilms that present hazards in the food industry.

Novel Method for Preparation of Pure and Iron-Doped Titania Nanotube Coated Wood Surfaces to Disinfect Airborne Bacterial SpeciesPseudomonas aeruginosaandStaphylococcus aureus

Abstract Nosocomial infections and food spoilage, caused by different airborne bacteria, is of major concern and titania nanostructure coated surfaces are effective in reducing pathogenic bacteria present in the indoor air. In the present study comparative photocatalytic disinfection ability of pure titania nanotube (TNT) and 1% iron-doped TNT coated wood surface, to disinfect airborne bacteria, has been examined. Prepared nanotubes (both pure and iron doped) were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Brunauer–Edward–Teller surface area measurement, and band gap energy calculations. Nanotubes were coated on wood surfaces using a novel and green method of coating using a natural resin as the binding agent. Coated wood surfaces were found effective in reducing important airborne bacterial species Pseudomonas aeruginosa (Gram negative) and Staphylococcus aureus (Gram positive) present in indoor air. With a 70% reduction in the population of P. aerug...