Surface Recontamination Research Articles

88. Increasing Bioburden of Candida auris Body Site Colonization is Associated with Environmental Contamination

Abstract Background Environmental contamination is suspected to play a key role in transmission of Candida auris in healthcare facilities. We recently showed that environmental surfaces near C. auris-colonized patients are commonly recontaminated within hours after disinfection. Clinical factors contributing to environmental contamination are not well characterized. Methods We conducted a multi-regional (Chicago, IL; Irvine, CA) prospective study of environmental contamination associated with C. auris colonization at six long-term care facilities (LTCF) and 1 acute-care hospital (ACH). On day of sampling, 5 participant body sites were cultured once, followed by routine daily room cleaning by facility staff, then targeted disinfection of high-touch surfaces with hydrogen peroxide wipes by research staff. Surfaces were cultured for C. auris using pre-moistened sponge-sticks and neutralizer immediately pre- and post-disinfection, and 4, 8, and 12 hours post-disinfection. We calculated the odds of surface recontamination after disinfection as a function of body site colonization with C. auris using generalized estimating equations to account for clustering among multiple surfaces within timepoints, patients, and facilities. Models included an interaction between facility type and colonization. Results C. auris was cultured from ≥1 body site in 41 participants (12 ACH and 29 LTCF patients, 205 body sites) on day of sampling. Proportion of body sites colonized did not vary by facility type (Table). Although environmental contamination rates were similar prior to disinfection [ACH 38% (n=60 samples) vs LTCF 29%, (n=145 samples), p=0.209)], the proportion of surfaces recontaminated between 4–12 hours after disinfection was higher in ACH vs LTCF (n=574 samples) (Figure). Number of body sites colonized with C. auris was associated with higher odds of environmental recontamination [ACH: OR 2.16 (95% CI 1.63–2.88), p< 0.001; LTCF: OR 1.40 (95% CI 1.07–1.84), p=0.015; Interaction ACH vs LTCF p< 0.001]. Conclusion The number of body sites colonized was associated with odds of C. auris environmental contamination. Differences in environmental recontamination by facility type may be related to greater provider-patient interactions in ACH as a driving factor. Disclosures Gabrielle M. Gussin, MS, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products Raveena D. Singh, MA, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products Raheeb Saavedra, AS, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products Nicholas M. Moore, PhD, D(ABMM), Abbott Molecular: Grant/Research Support|Cepheid: Grant/Research Support Susan S. Huang, MD, MPH, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Molnlyke: Conducted clinical studies in which hospitals received contributed antiseptic product|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic product Mary K. Hayden, MD, Sanofi: Member, clinical adjudication panel for an investigational SARS-CoV-2 vaccine.

Sonochemical decontamination of magnesium and magnesium-zirconium alloys in mild conditions

UNGG cladding nuclear wastes constitute a huge volume of Mg-based materials that raises economic and safety concerns, particularly due to their radioactivity coupled to the potential generation of H2 gas under deep underground disposal. Their significant decontamination would result in more secure and less expensive storage, with a better containment of the separated long-lived radioisotopes that could enter in a classical channel. Sonication of genuine UNGG cladding materials and simulants at 345 kHz in 0.01 M oxalic acid solution (20 °C) allowed the structuring of their surfaces with the observation of homogeneously distributed craters of 20–40 µm in diameter. After a thorough characterization and comparison of the ultrasound effects generated at the surface, the various samples were artificially contaminated and characterized before sonication. The complete and rapid sonochemical decontamination of Mg-based materials was then observed, in addition to the removal of the carbon layer promoting corrosion on the inner UNGG cladding. The extension of sonication allows the neo-formed brucite (Mg(OH)2) and zirconium-based phases to accumulate on the surface, thus contributing in a slight but continuous surface recontamination process. This phenomenon results from the re-adsorption of uranyl cations from the solution which can be avoided by optimizing the duration of treatment.

XPS, ToF SIMS and wettability analyses on Ni surfaces after Ar-H2 RF plasma treatment: An efficient and optimized plasma treatment approach

Electroless Ni plating is widely used for its properties such as wear resistance, uniform coating and excellent brazing and solderability. In electronic and mechatronic applications, the chemical composition of the Ni layer and its surface quality still remains elusive and improvisation of Ni layer surface quality is vital. This research work investigates the surface properties of Ni films subjected to Ar-H2 RF plasma treatment. Plasma treatment parameters are defined by utilizing D-Optimal design of experiments. A precise mapping of the evolution of Ni surface global chemical composition is obtained using an XPS. Principal component analysis on XPS mapping coupled with 3D ToF-SIMS chemical cartography enables precise identification of the different oxidation states of nickel and their distribution in the plasma-treated nickel samples. The nickel surface wettability is then determined using the classical sessile drop technique. The findings of the study enable to define the plasma optimal power and accomplish the best compromise between the positive effects of the surface decontamination and the negative effects of the surface recontamination. The optimized plasma treatment succeeds to modify the surface nature of the nickel from hydrophobic to strongly hydrophilic. It demonstrates that the Ar-H2 plasma treatment is a very efficient process to increase the Ni surface wettability and thereby to improve the electronic and mechatronic assembly processes.

Long-term PAH monitoring results from the Anacostia River active capping demonstration using polydimethylsiloxane (PDMS) fibers

In this paper, the long-term monitoring results for hydrophobic organic compounds, specifically polycyclic aromatic hydrocarbons (PAHs), from a field demonstration of capping contaminated sediments at the Anacostia River in Washington DC are presented and analyzed. In situ pore water concentrations in field-contaminated sediments in the demonstration caps were quantified using a polydimethylsiloxane (PDMS)-based passive sampling device. High resolution vertical pore water concentration profiles were measured using the device and were used to infer fate and transport of polycyclic aromatics hydrocarbons (PAHs) at the site. The derived pore water concentrations were compared with observed bioaccumulation and solid-phase concentration profiles to infer contaminant migration rates and mechanisms. Observed pore water concentrations were found to be a better predictor of bioaccumulation than solid-phase concentrations. Solid-phase concentrations were low in cores which implied containment of contamination; however pore water profiles showed that contaminant migration had occurred in the first few years after cap placement. The discrepancy is the result of the low sorption capacity of the sand. Because of surface re-contamination, low sorption capacity in the demonstration caps and strong tidal pumping effects, steady state contaminant profiles were reached in the caps several years after placement. Despite re-contamination at the surface, steady state concentrations in the capped areas showed decreased contamination levels relative to the control area.

Bacterial re-contamination of surfaces of food processing lines during cleaning in place procedures

The possible contamination of surfaces of food processing lines during cleaning in place (CIP) procedures was investigated. Experiments were focused on surface contamination of straight pipes and a two-way valve, chosen as an example of complex pieces of equipment. Pipes and a two-way valve were inserted into a CIP rig, at the same time as a series of pipes highly contaminated with spores of three Bacillus cereus strains, with various surfaces properties. Following a CIP procedure, performed in conditions close to those encountered in food industries, the contamination level of the various items was estimated. A significant surface contamination occurring during CIP was evidenced, depending on the spore surface properties. Similarly to previously reported observations, when spores were suspended in optimal adhesion conditions (suspension in water at 20 °C), the re-adhesion phenomenon was controlled by the flow pattern and contamination levels inside the valve were significantly higher than in tubes. Cleaning strategies should therefore take into account the re-adhesion phenomenon to limit the risk of contamination by the process line.

Photoemission monitored cleaning of pure and implanted tungsten photocathodes by picosecond UV laser

New results about picosecond laser cleaning of pure and implanted tungsten photocathodes are reported. During the transport from the preparation cell to the experimentation cell, the exposure of photocathodes to air leads to the contamination and the formation of surface oxides. Before any photocurrent measurement, in situ cleaning of surfaces is required. The surface cleaning effects are investigated in high vacuum (5×10−8 Torr) by using a picosecond mode-locked Nd3+:YAG laser with fifth order harmonic generator (λ=213 nm, τ=16 ps, repetition rate 10 Hz) irradiation. This non-destructive processing allows real-time monitoring by measuring continuously the surface photocurrent. During cleaning, the photocurrent increases versus time and tends to reach a plateau, depending on the pressure in the vacuum cell. The influence of the laser energy density and the effects of surface recontamination by residual gas are investigated. A phenomenological model is developed to describe the laser cleaning. Fitting the experimental data of photoemitted charges with calculated values given by this model is able to estimate the contamination rate and the work function at the surface during the cleaning.

Control of Listeria monocytogenes on the surface of frankfurters by acid treatments

Small numbers of Listeria monocytogenes can be isolated from packaged frankfurters. Based on previous work from this laboratory, these L. monocytogenes cells undoubtedly represent surface recontamination during peeling and packaging. We investigated organic acid dips just prior to packaging as a secondary lethal step to destroy L. monocytogenes and observed both bacteriocidal and bacteriostatic effects depending on the concentration of acid used. Acetic acid when combined with citric acid (at 2·5% each) restricted the growth and development of L. monocytogenes on frankfurters stored vacuum-packaged at 5°C for up to 90 days. Other acids individually, such as lactic acid (5%) and acetic acid (5%), also suppressed the organism. A dose response effect was observed for all acids tested. A simple 2 min surface rinse in saline was adequate to remove L. monocytogenes from frankfurter surfaces and gave recoveries similar to a stomacher method. The acid treatments appeared to be lethal and did not injure the organism. Overall, organic acid treatments appear to provide a secondary lethal step in frankfurter processing and could be an additional factor in limiting the presence of L. monocytogenes in frankfurters.

Desorbed gas flow rate and surface composition of metal alloys

Various methods of producing technically-clean stainless steel surfaces for special applications by means of soft procedures, i.e. without removing metal atoms, have been investigated, and a comparison between contamination of obtained surfaces has been made by means of total and partial desorbed flow rates and by AES and XPS analyses. Differences in residual contamination, and recontamination of surfaces due to exposure to air have been determined; results suggest that the best procedure could involve a steam degreasing followed by heat treatment and maintenance in nitrogen to prevent recontamination.

Quantitative microanalysis of oxygen in zirconium by Auger electron spectroscopy

Calibration curves for quantitative microanalysis of oxygen in zirconium by Auger electron spectroscopy have been derived from studies of well-characterized standards using a PHI 590A SAM. Knowledge of the intensity-energy response function of this instrument assures long-term reproducibility and may permit transfer of the results. Auger electron spectra were recorded in the pulse-counting mode from surfaces that had been thoroughly cleaned by argon-ion sputter etching and therefore incorporate any preferential sputtering effects. Surface recontamination by reactive constituents of the residual gas was determined to be unimportant for short analysis times in clean ultrahigh vacuum. Electron-stimulated desorption of oxygen was found to be significant at high incident electron-beam current densities and was accounted for empirically. Linear calibration curves were obtained using O and Zr peak areas measured above simple tangent backgrounds.

Ultra cold neutron life times in glow discharge cleaned bottles

Life times of ultra cold neutrons in tubes made of various materials have been increased with improvement of surface cleanliness. With glow discharge cleaning in vacua of only 10−4–10−3 torr, life times for long storage periods were obtained that differ by less than a factor of 2 from calculated values in the case of stainless steel and aluminium and by a factor of 3 for quartz. Surface recontamination is slow at the achieved level and approaches a stable value well below that before cleaning. A temperature dependence of ultra cold neutron reflection loss rates was observed. A direct correlation between reflection losses and the surface hydrogen concentration was established. We conclude that for smooth surfaces of materials with low reaction cross section, losses are mainly caused by upscattering on tightly bound hydrogen. The probability is discussed that the remaining losses are due to still incomplete cleanliness of the surface caused by hydrogen recontamination from the bulk and the atmosphere.

In situ investigation of substrate surface recontamination during glow-discharge sputter cleaning

In situ investigation of substrate surface recontamination during glow-discharge sputter cleaning

In situ investigation of substrate surface recontamination during glow‐discharge sputter cleaning

In the applications of thin film technology, the chemical nature of the substrate surface is known to affect the film/substrate interactions. Undesirable contaminants in the interfacial region may affect film nucleation, adhesion, and electrical or optical properties. Often, glow‐discharge sputter cleaning is used as a surface preparation technique prior to thin film deposition. Since this method of sputter cleaning is performed in a gaseous environment where the mean free path of the sputtered atoms is short, there is a possibility of surface recontamination by material sputtered from the substrate and from surrounding fixturing. In this investigation, we have used soft‐x‐ray appearance‐potential spectroscopy to monitor in situ the substrate surface composition after sputter cleaning with both dc and rf discharges. Data are presented which show that common contaminants such as carbon and oxide layers may be adequately removed by either dc or rf glow‐discharge sputter cleaning. Direct current sputter clea...

Radioactive contamination and its removal by ultrasound

UNGG cladding nuclear wastes constitute a huge volume of Mg-based materials that raises economic and safety concerns, particularly due to their radioactivity coupled to the potential generation of H2 gas under deep underground disposal. Their significant decontamination would result in more secure and less expensive storage, with a better containment of the separated long-lived radioisotopes that could enter in a classical channel. Sonication of genuine UNGG cladding materials and simulants at 345 kHz in 0.01 M oxalic acid solution (20 °C) allowed the structuring of their surfaces with the observation of homogeneously distributed craters of 20–40 µm in diameter. After a thorough characterization and comparison of the ultrasound effects generated at the surface, the various samples were artificially contaminated and characterized before sonication. The complete and rapid sonochemical decontamination of Mg-based materials was then observed, in addition to the removal of the carbon layer promoting corrosion on the inner UNGG cladding. The extension of sonication allows the neo-formed brucite (Mg(OH)2) and zirconium-based phases to accumulate on the surface, thus contributing in a slight but continuous surface recontamination process. This phenomenon results from the re-adsorption of uranyl cations from the solution which can be avoided by optimizing the duration of treatment.

Surface Cleaning by Cathode Sputtering

Evidence is presented to indicate that surface recontamination from background gases may be a significant factor in quantitative sputtering measurements, even for beam current densities of 0.1 ma/cm2 and operating pressures of 5×10−5 mm of Hg. An oversimplified mechanism is discussed which leads to criteria for a cleansurface sputtering experiment.

Fine grinding at supercritical speed : R. T. Hukki. Mining Engineering, v. 10; American Institute of Mining and Metallurgical Engineers, transactions, v. 211, May 1958, p. 581–591

<dm:abstracts xmlns:dm="http://www.elsevier.com/xml/dm/dtd"><ce:abstract xmlns:ce="http://www.elsevier.com/xml/common/dtd" view="all" class="author" id="aep-abstract-id5"><ce:section-title>Publisher Summary</ce:section-title><ce:abstract-sec view="all" id="aep-abstract-sec-id6"><ce:simple-para id="fsabs008" view="all">Surface preparation is critical to the nucleation and interface formation steps of the coating process, and is an essential step in all vacuum coating processes. Surface preparation includes not only cleaning but, in some cases, modification of the chemical, morphological, or mechanical properties of the surface or the near-surface region. A few external cleaning techniques have been developed specifically for vacuum coating or were initially used for vacuum coating. These include ultraviolet-ozone oxidative cleaning and sputter (physical) cleaning. Recontamination of surfaces in the deposition chamber can be a major problem. In addition to the obvious problems of backstreaming, flaking, and wear particles, particles can be formed by vapor-phase nucleation of the vaporized material. The preparation of “vacuum surfaces” in the deposition chamber is important in generating a clean vacuum environment rapidly. Stripping and reclamation of substrates, fixtures, and liners can be important to economical vacuum coating. Dispersion hardening is done in vacuum by ion implantation of one or several species or in plasma by ion bombardment and heating by reactive species.</ce:simple-para></ce:abstract-sec></ce:abstract></dm:abstracts>