Antibacterial effect of TiO2 modified with poly-amidoamine dendrimer – G3 on S. aureus and E. coli in aqueous solutions

This study investigated the bacterial removal using TiO2 nanoparticles (NPs) modified with poly-amidoamine dendrimer macromolecule (PAMAM, G3). The PAMAM G3/TiO2 (nanohybrid) was used to specify antibacterial properties via broth microdilution (MBC-Minimum Bactericidal Concentration and MIC-Minimum Inhibitory Concentration- determination), paper disc diffusion, and surface plate count methods. The nanohybrid was characterized via the different techniques. The effects of different factors including initial bacteria count, run time, solution pH, and the nanohybrid concentration were studied. The nanohybrid cytotoxicity was studied on AGS and MKN45 cells line by MTT assay. It was revealed that the nanohybrid was effective in intercepting both bacterial strains growth. The MIC value for S. aureus and E. coli were determined to be 4 and 2 μg/mL, respectively. The MBC value for both strains were calculated to be 32 μg/mL. The results showed removal efficiency of 100% for S. aureus and E. coli bacteria in optimum situation. The decrease in cell viability in the dosage of 32 μg/mL after 72 h treatment for AGS and MKN45 cells line were shown to be 6.2 and 4.6%, respectively. The nanohybrid was able to decrease the S. aureus and E. coli count in solution, which meets the drinking water criterions aligned with WHO guidelines.

The Effect Ultrasound and Surfactants on Nanobubbles Efficacy against Listeria innocua and Escherichia coli O157:H7, in Cell Suspension and on Fresh Produce Surfaces

Removing foodborne pathogens from food surfaces and inactivating them in wash water are critical steps for reducing the number of foodborne illnesses. In this study we evaluated the impact of surfactants on enhancing nanobubbles’ efficacy on Escherichia coli O157:H7, and Listeria innocua removal from spinach leaves. We evaluated the synergistic impact of nanobubbles and ultrasound on these two pathogens inactivation in the cell suspension. The results indicated that nanobubbles or ultrasound alone could not significantly reduce bacteria in cell suspension after 15 min. However, a combination of nanobubbles and ultrasonication caused more than 6 log cfu/mL reduction after 15 min, and 7 log cfu/mL reduction after 10 min of L. innocua and E. coli, respectively. Nanobubbles also enhanced bacterial removal from spinach surface in combination with ultrasonication. Nanobubbles with ultrasound removed more than 2 and 4 log cfu/cm2 of L. innocua and E. coli, respectively, while ultrasound alone caused 0.5 and 1 log cfu/cm2 of L. innocua and E. coli reduction, respectively. No reduction was observed in the solutions with PBS and nanobubbles. Adding food-grade surfactants (0.1% Sodium dodecyl sulfate-SDS, and 0.1% Tween 20), did not significantly enhance nanobubbles efficacy on bacterial removal from spinach surface.

Contribution of IL-38 in Lung Immunity During Pseudomonas Aeruginosa-Induced Pneumonia

Objective: Interleukin-38 (IL-38), a new type of cytokine, is involved in processes such as tissue repair, inflammatory response, and immune response. However, its function in pneumonia caused by Pseudomonas aeruginosa is still unclear.Methods: In this study, we detected circulating IL-38 in adults affected by pneumonia caused by P. aeruginosa. The P. aeruginosa-induced pneumonia WT murine model was adopted to evaluate the effect of IL-38 on Treg differentiation, cell apoptosis, survival, tissue damage, inflammation, and bacterial removal.Results: IL-38 is insufficiently secreted in patients who died of P.A. pneumonia.Recombinant IL-38 improved survival, whereas anti-IL-38 antibody reduced survival in the experimental pneumonia murine model. IL-38 exposure reduced the inflammatory response, as suggested by the lung injury, and reduced cytokine levels (IL-1β, IL-6, IL-17A, TNF-α, and CXCL-1, but not IL-10). It also increased bacterial clearance and reduced cell apoptosis in the lungs. Furthermore, IL-38 was shown to reduce TBK1 expression in vitro when naïve CD4+ T lymphocytes were differentiated to Tregs and played a protective role in P.A. pneumonia.Conclusions: To summarize, the above findings provide additional insights into the mechanism of IL-38 in the treatment of P.A. pneumonia.

Utilization of Rice Husk, an Abundant and Inexpensive Biomass in Porous Ceramic Membrane Preparation: A Crucial Role of Firing Temperature

The influence of firing temperature on characteristics and bacterial filtration of the porous ceramic membrane prepared from rice husk (20 wt%) and kaolin has been investigated. As firing temperatures increased from 900 to 1100°C, the compressive strength of membrane increased from 555.3 N/cm2 to 2992.3 N/cm2, whereas the porosity decreased from 49.4 to 30.2% due to structural condensation and mullite formation. The condensation caused pore contraction that finally improved bacterial removal efficiency from ~90% to 99%. The results suggested that the porous ceramic membrane prepared from rice husk and kaolin should be fired at ~1050°C to attain both strength and filtration efficiency.

Bacterial removal in flattened root canals with different tapers of ProDesign Logic single-file system

Objective: This study evaluated the bacterial removal in flattened root canals after preparation with different tapers of ProDesign Logic instruments. Methodology: Fifty-five mandibular incisors with flattened root canals were contaminated with a pure culture of Enterococcus faecalis ATCC 29212 for 21 days at 37ºC. Root canals preparation was performed using ProDesign Logic and 0.9% sterile saline solution for irrigation. The specimens were randomly allocated to three experimental groups (n = 15) according to the taper of the instrument used: 25.03, 25.04, or 25.06. Intracanal bacteriological samples were taken before (S1) and after (S2) preparation and the number of colony-forming units per milliliter (CFU/mL) was calculated. Differences in bacterial counts before and after treatment, within each group, were analyzed by the paired t-test. Groups were compared by ANOVA with a post hoc test. The level of significance was set at p <0.05. Results: Mature biofilm formation was confirmed at root canal walls by scanning electron microscopy. Bacterial colonies were significantly reduced in all experimental groups at S2 compared to S1 (p <0.001). No significant difference was observed between groups regarding the percentage of bacterial reduction (p >0.05). Conclusion: Preparation of flattened root canals using ProDesign Logic instruments with tapers of 0.03, 0.04 and 0.06 resulted in similar planktonic and bacterial biofilm reduction. None of the instruments rendered root canals completely free of bacteria.

Relationships between abiotic and biotic variables in a maturation pond and their influence on E. coli removal

The effects of depth and climate seasonality on zooplankton, algal biomass, coliforms and Escherichia coli in a small full-scale shallow maturation pond receiving pre-treated domestic wastewater were evaluated during a tropical climatic seasonal cycle. The experiment revealed that the zooplankton community was dominated by rotifers and protozoans, and concentrations were influenced by seasonality. A negative correlation between zooplankton, and pH, Dissolved Oxygen, temperature and ultraviolet radiation, and Chlorophyll-a and Escherichia coli were observed at all depths. The major driving forces influencing Escherichia coli were pH, Dissolved Oxygen, ultraviolet radiation and the zooplankton. A significant difference between Escherichia coli removal throughout the three different depths were observed. Both bacterial and zooplankton concentrations were greater closer to the bottom of the pond, therefore reinforcing the integral role of solar radiation on bacterial removal. These results give an insight on the dynamics of these groups in pond systems treating domestic wastewater, by correlating the variation of zooplankton with biotic and abiotic variables and seasonal changes in a tropical climate, where few studies have been performed on this topic.

Well-Dispersed Silver Nanoparticles on Cellulose Filter Paper for Bacterial Removal

In this study, a polydopamine (PDA) and polyethyleneimine (PEI)-assisted approach was developed to generate well-distributed PDA/PEI/silver (PDA/PEI/Ag) nanocomplexes on the surfaces of commercial cellulose filter papers to achieve substantial bacterial reduction under gravity-driven filtration. PDA can bind to cellulose paper and act as a reducer to produce silver nanoparticles (AgNPs), while PEI can react with oxidative dopamine and act as a dispersant to avoid the aggregation of AgNPs. The successful immobilization of PDA/PEI/Ag nanocomplexes was confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were used as pathogen models to test the efficacy of the PDA/PEI/Ag nanocomplex-incorporated filter papers. The PDA/PEI/Ag nanocomplex-incorporated filter papers provided a substantial bacterial removal of up to 99% by simple gravity filtration. This work may be useful to develop a feasible industrial production process for the integration of biocidal AgNPs into cellulose filter paper and is recommended as a local-condition water-treatment technology to treat microbial-contaminated drinking water.

Simultaneous denitrification and hexavalent chromium removal by a newly isolated Stenotrophomonas maltophilia strain W26 under aerobic conditions

Environmental contextIndustrial development has caused the release of hexavalent chromium and nitrates into the environment. Interactions of hexavalent chromium and nitrates with microorganisms are important both for understanding environmental behaviour and for treatment options. Bacterial removal of both chromium and nitrate was optimised in waters relevant to waste streams and the environment. Abstract An isolated strain of the bacterium Stenotrophomonas maltophilia strain W26, is shown to be capable of the simultaneous removal of nitrate and CrVI under aerobic conditions. Notably, 10mg L−1 of CrVI and 500mg L−1 of nitrate were reduced by 92.6% and 85.2%, respectively, by strain W26. Results showed that an excellent denitrification efficiency of 96.0% could be reached at the optimal conditions of a C/N ratio of 10, using a carbon source of trisodium citrate, at pH 7.5, and a nitrate concentration of 500mg L−1. Strain W26 could also effectively remove high concentrations of CrVI (50mg L−1, 93.2%) and nitrate (700mg L−1, 97.4%). By using the N balance analysis, energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the denitrification and CrVI transformation processes were verified. CrVI, immobilised on the cell surface by W26, was reduced to CrIII, through interaction with of O=C and N-H groups. This study indicates that the isolated strain W26 has the potential to treat wastewater containing combined nitrate and CrVI contamination.