scholarly journals Chlorine disinfection against Legionella pneumophila biofilms

2020 ◽  
Vol 10 (4) ◽  
pp. 885-893
Author(s):  
Abdelwahid Assaidi ◽  
Mostafa Ellouali ◽  
Hassan Latrache ◽  
Hafida Zahir ◽  
Abdelaziz Karoumi ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Bacterial Resistance ◽  
Galvanized Steel ◽  
Opportunistic Pathogens ◽  
New Approach ◽  
Force Microscopy ◽  
Chlorine Disinfection ◽  
Atomic Force ◽  
Premise Plumbing ◽  
Planktonic Form

Abstract Premise plumbing promotes the regrowth and survival of opportunistic pathogens, such as Legionella pneumophila (L. pneumophila), especially within biofilms. The purpose of this study was to investigate the effectiveness of chlorine disinfection against L. pneumophila serogroup 1 and serogroup 2–15 planktonic form and biofilms. Planktonic cells were able to survive during the study period in the presence of chlorine at recommended free chlorine levels (0.2–0.5 mg/L). Biofilms were developed on galvanized steel and polyvinyl chloride (PVC) for 18 and 30 days and exposed to 50, 100, 150, and 200 mg/L for 2 hours. No colony appeared immediately after chlorination; however, persistent cells were able to tolerate treatment and continue to grow on subsequent days. The biofilm formation was evaluated by atomic force microscopy. This study demonstrates that the biofilm formed on the surfaces of plumbing materials increases bacterial resistance against high levels of chlorination. A new approach towards monitoring and eradicating L. pneumophila from water systems is required.

Visualization of molecular binding sites at the nanoscale in the lift-up mode by amplitude-modulation atomic force microscopy

Nanoscale ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 4213-4220
Author(s):  
Tatsuhiro Maekawa ◽  
Takashi Nyu ◽  
Evan Angelo Quimada Mondarte ◽  
Hiroyuki Tahara ◽  
Kasinan Suthiwanich ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Molecular Recognition ◽  
Amplitude Modulation ◽  
Binding Sites ◽  
Local Distribution ◽  
New Approach ◽  
Molecular Binding ◽  
Force Microscopy ◽  
Atomic Force ◽  
Recognition Sites

We report a new approach to visualize the local distribution of molecular recognition sites with nanoscale resolution by amplitude-modulation atomic force microscopy.

The Investigation of Thin Protecting Layers on Roughened Galvanized Steel Surfaces Produced by Different Coating Methods

2008 ◽  
Vol 589 ◽  
pp. 433-438 ◽  
Author(s):  
Péter Németh ◽  
Ágnes Csanády ◽  
Katalin Papp ◽  
Anna C. Pintér ◽  
László Szabó ◽  
...  
Keyword(s):  
Thickness Distribution ◽  
Thin Layers ◽  
Galvanized Steel ◽  
Photoemission Spectroscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Coating Methods ◽  
Chemical States ◽  
Steel Surfaces ◽  
Thickness Variations

Protective, chromate substitute thin layers on roughened galvanized surfaces produced at OCAS (Arcelor, Belgium) were characterized and compared using Scanning Electron Microscopy (SEM+EDS), Atomic Force Microscopy (AFM), Nanoindentation and X-ray Photoemission Spectroscopy (XPS). EDX maps, line scans and point analyses obtained at various places of the surfaces have shown differences between the CVD and silane nanolayers in the matter of thickness distribution and composition. At cross-section specimens the thickness of the layers could be shown. The hardness differences caused by layer thickness variations are hard to follow by nanoindentation as the penetration depth of the indenter is much larger than the thickness of the coatings. XPS measurements can distinguish between the chemical states of silicon in CVD and silane coatings.

scholarly journals Critical Review: Propensity of Premise Plumbing Pipe Materials to Enhance or Diminish Growth of Legionella and Other Opportunistic Pathogens

Pathogens ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 957
Author(s):  
Abraham C. Cullom ◽  
Rebekah L. Martin ◽  
Yang Song ◽  
Krista Williams ◽  
Amanda Williams ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Chemistry ◽  
Legionella Pneumophila ◽  
High Surface ◽  
Metallic Copper ◽  
Health Concern ◽  
Future Research ◽  
Opportunistic Pathogens ◽  
Premise Plumbing ◽  
Pipe Materials

Growth of Legionella pneumophila and other opportunistic pathogens (OPs) in drinking water premise plumbing poses an increasing public health concern. Premise plumbing is constructed of a variety of materials, creating complex environments that vary chemically, microbiologically, spatially, and temporally in a manner likely to influence survival and growth of OPs. Here we systematically review the literature to critically examine the varied effects of common metallic (copper, iron) and plastic (PVC, cross-linked polyethylene (PEX)) pipe materials on factors influencing OP growth in drinking water, including nutrient availability, disinfectant levels, and the composition of the broader microbiome. Plastic pipes can leach organic carbon, but demonstrate a lower disinfectant demand and fewer water chemistry interactions. Iron pipes may provide OPs with nutrients directly or indirectly, exhibiting a high disinfectant demand and potential to form scales with high surface areas suitable for biofilm colonization. While copper pipes are known for their antimicrobial properties, evidence of their efficacy for OP control is inconsistent. Under some circumstances, copper’s interactions with premise plumbing water chemistry and resident microbes can encourage growth of OPs. Plumbing design, configuration, and operation can be manipulated to control such interactions and health outcomes. Influences of pipe materials on OP physiology should also be considered, including the possibility of influencing virulence and antibiotic resistance. In conclusion, all known pipe materials have a potential to either stimulate or inhibit OP growth, depending on the circumstances. This review delineates some of these circumstances and informs future research and guidance towards effective deployment of pipe materials for control of OPs.

scholarly journals Development of a new hybrid approach combining AFM and SEM for the nanoparticle dimensional metrology

2019 ◽  
Vol 10 ◽  
pp. 1523-1536 ◽  
Author(s):  
Loïc Crouzier ◽  
Alexandra Delvallée ◽  
Sébastien Ducourtieux ◽  
Laurent Devoille ◽  
Guillaume Noircler ◽  
...  
Keyword(s):  
Hybrid Approach ◽  
Proof Of Concept ◽  
Characteristic Parameters ◽  
Dimensional Metrology ◽  
New Approach ◽  
Force Microscopy ◽  
Atomic Force ◽  
Spherical Silica ◽  
Spatial Dimensions ◽  
Complementary Nature

At this time, there is no instrument capable of measuring a nano-object along the three spatial dimensions with a controlled uncertainty. The combination of several instruments is thus necessary to metrologically characterize the dimensional properties of a nano-object. This paper proposes a new approach of hybrid metrology taking advantage of the complementary nature of atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques for measuring the main characteristic parameters of nanoparticle (NP) dimensions in 3D. The NP area equivalent, the minimal and the maximal Feret diameters are determined by SEM and the NP height is measured by AFM. In this context, a kind of new NP repositioning system consisting of a lithographed silicon substrate has been specifically developed. This device makes it possible to combine AFM and SEM size measurements performed exactly on the same set of NPs. In order to establish the proof-of-concept of this approach and assess the performance of both instruments, measurements were carried out on several samples of spherical silica NP populations ranging from 5 to 110 nm. The spherical nature of silica NPs imposes naturally the equality between their height and their lateral diameters. However, discrepancies between AFM and SEM measurements have been observed, showing significant deviation from sphericity as a function of the nanoparticle size.

Corrosion Protection and Composition of Galvanized Steel Substrates by Bis-[3-(triethoxysilyl)-Propyl]Tetrasulfide and Gamma-Aminopropyltriethoxysilane

2011 ◽  
Vol 299-300 ◽  
pp. 333-336 ◽  
Author(s):  
Feng Jun Shan ◽  
Guo Chao Qi ◽  
Chang Sheng Liu
Keyword(s):  
Corrosion Current Density ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Galvanized Steel ◽  
Nacl Solution ◽  
Force Microscopy ◽  
Atomic Force ◽  
Immersing Method ◽  
Steel Substrates ◽  
Total Impedance

Compound silane films were prepared on galvanized steel by immersing method using mixture of bis-[3-(triethoxysilyl)propyl]tetrasulfide and γ-aminopropyltriethoxysilane. The corrosion resistance of galvanized steel substrates was compared after treatment with bis-[3-(triethoxysilyl)propyl]tetrasulfide, γ-aminopropyltriethoxysilane and their mixture in 3.5%NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy. The results indicated that corrosion current density of the mixed silane films was reduced evidently and self-corrosion pressure of that was shifted to left markedly and total impedance value of that increased about two orders of magnitude. The analytical characterisation was performed by Fourier transform infrared spectroscopy and atomic force microscopy. The results showed that bis-[3-(triethoxysilyl)propyl]tetrasulfide and γ-aminopropyltriethoxysilane were all connected with the former of films.

Effect of Inorganic/Organic Hybrid on the Wettability of Polymer Nanofibrous Membranes

2013 ◽  
Vol 8 (4) ◽  
pp. 155892501300800 ◽  
Author(s):  
Ning Wu ◽  
Ying Sun ◽  
Yanan Jiao ◽  
Li Chen
Keyword(s):  
Water Contact ◽  
Tem Analysis ◽  
New Approach ◽  
Force Microscopy ◽  
Organic Hybrid ◽  
Atomic Force ◽  
Hybrid Nanofibers ◽  
Nanofibrous Membranes ◽  
Fibrous Membranes ◽  
Composite Fibrous Membranes

We report a new approach for improving the wettability of a poly (vinyl acetate) (PVAc) nanofiber membrane. The pure PVAc and hybrid PVAc/titanium dioxide (TiO2) nanofibrous membranes can be obtained by electrospinning the PVA solution and PVA/TiO2 hybrid sol with different TiO2 contents, respectively. The resultant samples were characterized by scanning electron microscopy (SEM), nitrogen volumetric adsorption apparatus (NVAA), water contact angle (WCA), atomic force microscopy (AFM) energy dispersive X-ray spectroscopy (EDX) and transmission electronic microscopy (TEM). It was found that the WCA of composite fibrous membranes was decreased from 109 to 36° as the TiO2 content increased. The AFM, EDX and TEM analysis indicate that the wettability of PVAc/TiO2 hybrid nanofibers was mainly improved by surface roughness and surface hydrophilic groups.

scholarly journals Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp.

2020 ◽  
Author(s):  
Raymond M Hozalski ◽  
Timothy M LaPara ◽  
Xiaotian Zhao ◽  
Taegyu Kim ◽  
Michael B Waak ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Water Levels ◽  
Hot Water ◽  
Quantitative Microbial Risk Assessment ◽  
Opportunistic Pathogens ◽  
Bacterial Gene ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Commercial Cultivation ◽  
Premise Plumbing

The unprecedented widespread closing of buildings due to the COVID-19 pandemic has allowed water to stagnate in premise plumbing systems, creating conditions that may facilitate the growth of opportunistic pathogens. In this study, we flushed and collected samples from showers in buildings that had been unoccupied for approximately two months and quantified Legionella pneumophila using a commercial cultivation-based assay. In addition, all bacteria, Legionella spp., L. pneumophila, L. pneumophila serogroup 1, non-tuberculous mycobacteria (NTM), and Mycobacterium avium complex (MAC) were analyzed using quantitative PCR (qPCR). Despite low or negligible total chlorine in the stagnant pre-flush water samples, L. pneumophila were not detected by either method; Legionella spp., NTM, and MAC, however, were widespread. Using quantitative microbial risk assessment (QMRA), estimated risks of clinical illness from exposure to legionella and MAC via showering were generally low, but the risk of subclinical infection via Legionella spp. could exceed a 10-7 daily risk threshold if just a small fraction (≥0.1 %) of those legionellae detected by qPCR are highly infectious. Flushing cold and hot water lines rapidly restored a total chlorine (as chloramine) residual and decreased all bacterial gene targets to building inlet water levels within 30 min. Following flushing, the chlorine residual rapidly dissipated and bacterial gene targets rebounded, approaching pre-flush concentrations after 6 to 7 days of stagnation. These results suggest that stagnant water in premise plumbing may contain elevated levels of opportunistic pathogens; flushing, however, can rapidly improve water quality and reduce the health risk but the improvement will be short-lived if building disuse persists.

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