Silencing the nosocomial pathogen Serratia marcescens by glyceryl trinitrate

Background: Quorum sensing is a cell-to-cell communication system in bacteria that controls the production of virulence factors. Serratia marcescens is a causative agent of hospital-acquired infections that shows high resistance to antibiotics. This makes the treatment of these infections difficult. Quorum sensing regulates the production of virulence factors of S. marcescens such as prodigiosin, protease, swimming and swarming motilities and formation of biofilms. Inhibition of quorum sensing may be an alternative to antibiotic treatment to avoid emergence of resistance.Objectives: Testing the ability of glyceryl trinitrate to inhibit quorum sensing and virulence factors of Serratia marcescens.Methods: The inhibiting activities of sub-inhibitory concentration of glyceryl trinitrate against the quorum-sensing regulated violacein pigment in Chromobacterium violaceum CV026 was performed to evaluate the anti-quorum sensing effect of glyceryl trinitrate. The anti-virulence activity was assessed against prodigiosin, protease, biofilm formation in addition to swimming and swarming motilities.Results: Glyceryl trinitrate at at a concentration of 0.25 mg/ml produced significant inhibitory effects against violacein (67.01%), prodigiosin (82.67%), protease, swimming (36.72%) and swarming (79.31%) motilities and biofilm formation (87.83%).Conclusion: Glyceryl trinitrate is a quorum sensing and virulence inhibitor that may be useful in treatment of nosocomial infections caused by Serratia marcescens.Keywords: Serratia marcescens, quorum sensing, virulence, glyceryl trinitrate

Design of compact stop-band extended microstrip low-pass filters by employing mutual-coupled square-shaped defected ground structures

A new technique to reduce the size, improve the rejection in the stop-band of a low-pass filter using modified defected ground structure (DGS) is proposed. An equivalent circuit model is used to study the DGS characteristics. The parameters are extracted by using a simple circuit analysis method. Several comparisons between the EM-simulations and the circuit simulations of the new structure are demonstrated to show the validity of the proposed equivalent circuit model. We demonstrated that the filter can provide a sharp transition domain and a wide rejection in stop-band. To further verify the new technique, a filter employing the new deformed DGS is fabricated and measured. The agreement between the simulation and the measured results confirms the effectiveness of the proposed concept. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1107–1111, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23273Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58033/1/23273_ftp.pd

Repurposing metformin as a quorum sensing inhibitor in Pseudomonas aeruginosa

Background: Quorum sensing is a mechanism of intercellular communication that controls the production of virulence factors in Pseudomonas aeruginosa. Inhibition of quorum sensing can disarm the virulence factors without exerting stress on bacterial growth that leads to emergence of antibiotic resistance.Objectives: Finding a new quorum sensing inhibitor and determining its inhibitory activities against virulence factors of Pseudomonas aeruginosa PAO1 strain.Methods: Quorum sensing was evaluated by estimation of violacein production by Chromobacterium violaceum CV026. Molecular docking was used to investigate the possible binding of metformin to LasR and rhlR receptors. The inhibition of pyocyanin, hemolysin, protease, elastase in addition to swimming and twitching motilities, biofilm formation and resistance to oxidative stress by metformin was also assessed.Results: Metformin significantly reduced the production of violacein pigment. Significant inhibition of pyocyanin, hemolysin, protease and elastase was achieved. Metformin markedly decreased biofilm formation, swimming and twitching motilities and increased the sensitivity to oxidative stress. In the molecular docking study, metformin could bind to LasR by hydrogen bonding and electrostatic interaction and to rhlR by hydrogen bonding only.Conclusion: Metformin can act as a quorum sensing inhibitor and virulence inhibiting agent that may be useful in the treatment of Pseudomonas aeruginosa infection.Keywords: Metformin, Pseudomonas aeruginosa, quorum sensing, virulence inhibitio

Investigation of pulse dispersion in a carrier-based UWB system with LO leakage cancellation

Local oscillator (LO) leakage in a carrier-based ultrawideband (UWB) system is a major design concern. In many cases, mixer LO-RF isolation is not sufficient and the LO leakage is well above the useful UWB signal. However, this leakage can be substantially reduced by using a notch filter located before the UWB transmitting antenna as long as it will not lead to unacceptable signal distortion. Therefore, various filter parameters, such as the filter order and 3 dB rejection bandwidth, have been studied to see their effects on providing sufficient band rejection level to reduce the unwanted LO leakage while minimizing the transmitted pulse dispersion. Time domain simulations and measurements have been utilized to evaluate the pulse dispersion using both the relative signal's first pulse amplitude and the pulse time delay spread. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64339/1/20390_ftp.pd

Effectiveness of Shading Air-Cooled Condensers of Air-Conditioning Systems

In air-conditioning (A/C) systems with air-cooled condensers, the condensing unit has to be kept in the open for easy access to outdoor air in order to efficiently dissipate heat. During daytime, the solar radiation falling on the surfaces of the condenser and the high ambient temperatures can be detrimental for the energy performance. The effectiveness of shading the condensing unit to mitigate this adverse impact is investigated in this paper. A limiting analysis compares the performance of several A/C systems with ideal shade to those with ideal solar heat gain. The comparison is based on a theoretical model and data from equipment catalogs. The theoretical increase in the coefficient of performance (COP) due to shading is found to be within 2.5%. Furthermore, this small improvement in ideal efficiency decreases at higher ambient temperatures, when enhancements to efficiency are more needed. The actual efficiency improvement due to shading is not expected to exceed 1%, and the daily energy savings will be lower

Silencing the nosocomial pathogen Serratia marcescens by glyceryl trinitrate

Background: Quorum sensing is a cell-to-cell communication system in bacteria that controls the production of virulence factors. Serratia marcescens is a causative agent of hospital-acquired infections that shows high resistance to antibiotics. This makes the treatment of these infections difficult. Quorum sensing regulates the production of virulence factors of S. marcescens such as prodigiosin, protease, swimming and swarming motilities and formation of biofilms. Inhibition of quorum sensing may be an alternative to antibiotic treatment to avoid emergence of resistance. Objectives: Testing the ability of glyceryl trinitrate to inhibit quorum sensing and virulence factors of Serratia marcescens. Methods: The inhibiting activities of sub-inhibitory concentration of glyceryl trinitrate against the quorum-sensing regulated violacein pigment in Chromobacterium violaceum CV026 was performed to evaluate the anti-quorum sensing effect of glyceryl trinitrate. The anti-virulence activity was assessed against prodigiosin, protease, biofilm formation in addition to swimming and swarming motilities. Results: Glyceryl trinitrate at at a concentration of 0.25 mg/ml produced significant inhibitory effects against violacein (67.01%), prodigiosin (82.67%), protease, swimming (36.72%) and swarming (79.31%) motilities and biofilm formation (87.83%). Conclusion: Glyceryl trinitrate is a quorum sensing and virulence inhibitor that may be useful in treatment of nosocomial infections caused by Serratia marcescens

Effect of SPIO Nanoparticle Concentrations on Temperature Changes for Hyperthermia via MRI

Magnetic nanoparticles (MNPs) are being developed for a wide range of biomedical applications. In particular, hyperthermia involves heating the MNPs through exposure to an alternating magnetic field (AMF). These materials offer the potential for selectively by heating cancer tissue locally and at the cellular level. This may be a successful method if there are enough particles in a tumor possessing sufficiently high specific absorption rate (SAR) to deposit heat quickly while minimizing thermal damage to surrounding tissue. The current research aim is to study the influence of super paramagnetic iron oxides Fe3O4 (SPIO) NPs concentration on the total heat energy dose and the rate of temperature change in AMF to induce hyperthermia in Ehrlich carcinoma cells implanted in female mice. The results demonstrated a linearly increasing trend between these two factors

Continuous electrochemical generator of hypervalent iodine reagents: synthetic applications in flow

An efficient and reliable electrochemical generator of hypervalent iodine reagents has been developed. In the anodic oxidation of iodoarenes under flow conditions to hypervalent iodine reagents the use of electricity replaces hazardous and costly chemical oxidants. Unstable hypervalent iodine reagents can be prepared easily and coupled with different substrates to achieve oxidative transformations in high yields. The unstable electrochemically generated reagents can also easily be transformed into classic bench stable hypervalent iodine reagents via ligand exchange. The combination of electrochemical and flow chemistry advantages largely improves the ecological footprint of the overall process compared to conventional approaches

Glyceryl trinitrate blocks staphyloxanthin and biofilm formation in Staphylococcus aureus

Background: Staphylococcus aureus is an important nosocomial bacterium that is responsible for a number of infections that may be fatal. The treatment of such infections is limited by emergence of antibiotic resistance. Targeting virulence of Staphylococcus aureus may provide an alternative option to antibiotic that may bypass the emergence of resistant strains due to lack of stress on viability. Objectives: Investigation of the ability of glyceryl trinitrate (GTN) to inhibit staphyloxanthin, biofilm and tolerance to oxidative stress. Methods: The disk sensitivity method was used to detect the methicillin resistance of Staphylococcus aureus. The effect of sub-inhibitory concentration of GTN on biofilm formation, staphyloxanthin production and tolerance to oxidative stress was evaluated. Molecular docking study was used to investigate the ability of GTN to bind to dehydrosqualene synthase enzyme. Results: GTN showed a significant inhibition of biofilm, staphyloxanthin and tolerance to oxidative stress. In the molecular docking study, it was found that GTN could bind to dehydrosqualene synthase enzyme by hydrogen bonding,electrostatic interaction and pi-cation interaction. Conclusion: The present study revealed the ability of GTN to serve as a potential anti-virulence candidate for attenuation of S. aureus pathogenicity. DOI: https://dx.doi.org/10.4314/ahs.v19i1.10 Cite as: Abbas HA, Elsherbini AM, MA S. Glyceryl trinitrate blocks staphyloxanthin and biofilm formation in Staphylococcus aureus. Afri Health Sci. 2019;19(1). 1376-1384. https://dx.doi.org/10.4314/ahs.v19i1.1