Sample Surface Research Articles

Estimating depth-directional thermal conductivity profiles using neural network with dropout in frequency-domain thermoreflectance

Non-contact and non-destructive methods are essential for accurately determining the thermophysical properties necessary for the optimal thermal design of semiconductor devices and for assessing the properties of materials with varying crystallinity across their thickness. Among these methods, frequency-domain thermoreflectance (FDTR) stands out as an effective technique for evaluating the thermal characteristics of nano/microscale specimens. FDTR varies the thermal penetration depth by modifying the heating frequency, enabling a detailed analysis of the thermophysical properties at different depths. This study introduces a machine learning approach that employs FDTR to examine the thermal conductivity profile along the depth of a specimen. A neural network model incorporating dropout techniques was adapted to estimate the posterior probability distribution of depth-wise thermal conductivity. Analytical databases for both uniform and non-uniform thermal conductivity profiles were generated, and the machine learning model was trained using these databases. The effectiveness of the predictive model was confirmed through assessments of both uniform and non-uniform thermal conductivity profiles, achieving a coefficient of determination between 0.96 and 0.99. For uniform thermal conductivity, the method attained mean absolute percentage errors of 1.362% for thermal conductivity and 3.466% for thermal boundary conductance (compared to actual values in the analytically calculated database). In cases of non-uniform thermal conductivity, the prediction accuracy decreased, particularly near the sample's surface, primarily due to the limited availability of machine learning data at higher heating frequencies.

Laser-induced damage thresholds in SiO2-coated aluminum mirrors under various ultrashort pulse widths

The influence of laser temporal parameters on the laser-induced damage threshold (LIDT) is particularly complex due to the variation and uncertainty in damage mechanisms associated with different pulse widths, especially in the range that bridges transitional damage mechanisms. Metallic mirrors are ideally suited for ultrashort pulse optical systems owing to their broad spectral range. A comprehensive understanding of the damage behavior of metallic mirrors under ultrashort pulse widths is crucial for optimizing their performance and manufacturing processes. Consequently, a laser damage testing platform was established in the laboratory to conduct 1-on-1 and area-based damage testing method on SiO2-coated aluminum mirrors, covering a pulse width range of 0.2 to 11 ps. The experimental results revealed two transitions in the LIDT from 0.2 to 11 ps. Specifically, within the 0.3 to 8 ps pulse width range, the LIDT inversely correlated with the pulse width, adhering to a power-law relationship. Conversely, for pulse widths below 0.3 ps and between 8 and 11 ps, the LIDT positively correlated with the pulse width. Observations using optical microscopy and scanning electron microscopy (SEM) exhibited the damage morphology at different pulse widths, which indicated that damage initially occurred in the SiO2 dielectric film on the sample surface, demonstrating a transition in the laser damage mechanism across the experimental pulse width range.

Optimization of multiple outputs of electric arc spray coating parameters for EN AW 7020-T6

Electric arc spray coating (EASC) is a method used to protect aluminum materials from corrosion, but there is no optimization in the literature using Al99.99 coating wire for EN AW 7020 alloy. The presented study aims to optimize the EASC process parameters (voltage, amperage, spray distance, and number of passes) for EN AW 7020-T6 aluminum samples. The experimental design of selected factors was made with Taguchi L9(34) orthogonal array and the aftermath of optimum values for coating were obtained with the TOPSIS multicriteria decision-making method. Output parameters respectively; pull-off strengths of coating were determined in compliance with the ASTM D4541 standard, the coating thicknesses were measured with a 3D profilometer, and the porosity values for cross-section were analyzed by optical microscope according to ASTM E2109 standard. After determining the optimum parameters, the substrates were coated and the crystallographic analysis of the coated samples was performed by XRD technique and electrochemical corrosion potential values were determined by galvanostat/potentiostat device in 3.5% NaCl solution. In exfoliation corrosion (EXCO) tests performed according to ASTM G34-1 standard, EXCO damage was detected on the surfaces of uncoated samples and graded as EA. In the EXCO tests with coated samples, no corrosion damages were observed on the coatings and they were rated with an N grade. The Al99.99 coating significantly improved the EXCO resistance of EN AW 7020-T6, reducing the corrosion rate by almost 100%. EXCO tests with uncoated and coated samples proved that the Al99.99 coating acts as a barrier to protect the substrate. Optimized Al99.99 coating offers a promising solution to improve the corrosion resistance of EN AW 7020-T6 aluminum alloys and extend their service life in harsh environments.

Inferring microalgae density and net ecosystem production on soft sediments using infrared imaging

AbstractMeasuring microalgae density in soft‐sediment benthos has challenges for even the most sophisticated methods. If the goal is to assess the photosynthetic potential of epipelon, then microalgae should be sampled only at the surface of the benthos to the depth of light penetration. Furthermore, microalgae density may show spatial and temporal variability that can only be captured by using many point samples and nondestructive sampling. Here, we use simple near‐infrared (NIR) imagery to assess surface density of microalgae in soft underwater sediments and to infer their photosynthetic capacity. In lab studies, NIR imagery gives estimates of epipelon density that are strongly correlated with standard chlorophyll a (Chl a) assays using pigment extraction and fluorometry ( = 0.70), but NIR imagery is better able to separate experimental treatments. In analyses of sediment samples from a lake, NIR imagery gives estimates of epipelon Chl a density that are strongly correlated to net ecosystem production (NEP). Near‐infrared imagery also gives a fine‐grained assessment of the spatial distribution of epipelon that helps to explain the relationship between epipelon density and NEP. Finally, images from an underwater NIR camera over the course of a wind disturbance event give estimates of the relative density of microalgae that is buried and is likely to be, at least temporarily, photosynthetically inactive. These results show that NIR imagery provides an easy and nondestructive method for sampling surface densities of microalgae which is particularly suitable for remote field locations and for educational settings in which students can generate results with cheap and robust equipment.

Quantitative Analysis of Grain Boundary Segregation of Boron in Steel with Secondary-Ion Mass Spectrometry in Comparison to Atom Probe Tomography.

To identify the origin of high intensities of BO2- signals on grain boundaries (GBs) in boron (B) mapping using secondary-ion mass spectrometry (SIMS), atom probe tomography analysis was performed on high-brightness GBs in the steel with the addition of B. Homogeneous segregation of B atoms as a solid solution, rather than continuous GB precipitation of fine boride, was observed at the GBs. The amounts of B segregation varied between the GBs. An estimation of the incident angle of the GB from the sample surface in each GB indicated that the high-brightness GBs always have smaller incident angles than the median angle under the assumption of random GB orientation, resulting in an increase in the GB area in the SIMS analyzed region. The product of the actual B segregation amount and area increase factor roughly corresponded to the apparent B intensity of the GB in B-mapping with SIMS. The high brightness in the B-mapping originated mainly from small incident angles of GB from the sample surface in the steel. The incident angle of the GB plane must be considered for quantification of GB segregation of B in the SIMS analysis.

Laser-Induced Breakdown Spectroscopy Using 2D Structured Light: A Case of Spectral Signal Enhancement on Metal Samples.

Laser-induced breakdown spectroscopy (LIBS), an elemental detection technique with great potential, faces many problems mainly caused by the nonideal plasma properties in the detection window. The 2D laser energy distribution on the sample surface has a crucial impact on the plasma properties and spectral emission. However, relevant studies are still limited, lacking a good degree of freedom (DOF) to systematically explore its influence. In this work, 2D structured light was generated by using a spatial light modulator (SLM). Various focal patterns with different cross-section areas were tested using metal samples so that the effects of the focal spot structure and cross-section area could be separated. The arrow-target and anticone of 200 μm diameter resulted in a line enhancement factor of more than 3 for a pure aluminum sample and a factor of about 6 for the pure copper sample over that without beam modulation. A significant improvement in the signal-to-noise ratio and a reduction in the limit of detection (LOD) of Cr, Mn, Si, Cu, and Al by a factor of about 6 were also achieved with the bearing steel sample. To better understand the mechanism behind such improvements, time-resolved spectra were measured, from which the electron density and plasma temperature evolution were calculated. The results showed that with anticone and arrow-target patterns, the electron density was increased by more than 50%, while the plasma temperature varied less than 500 K, suggesting an evident ablation enhancement. The fast images of plasma self-emission proved that the laser energy distribution substantially influenced the morphology of the plasma plume. The plasma cores produced by the anticone and arrow-target focal patterns were more compact after the expansion and cooling process, which could reduce the mixing of plasma plumes and ambient air. Thus, with the first application of SLM in LIBS, focal spot structures of micrometer resolution could be rationally designed and generated with a high DOF. Substantial spectral signal enhancement and a much lower LOD were achieved. This study provides new insights into the role of focal patterns in plasma properties, suggesting the future possibility of plasma control using structured light.

Investigation of quaternary ammonium compound resistance in Staphylococcus aureus strains isolated from several foods and food production facilities

AbstractQuaternary ammonium compounds (QACs) are the most significant disinfectants utilised to control the contamination of Staphylococcus aureus in food establishments. S. aureus is a significant pathogen that carries genes responsible for resistance to QACs, which pose a risk to public health and food safety. The objective of the study was to investigate the prevalence of QAC genes (qacA/B, qacC, qacG, qacH, qacJ, and smr) and benzalkonium minimal inhibitory concentration (MIC) values in S. aureus strains isolated from food products and food production facilities (n = 200). The analysis results indicated that the qacC gene was the most frequently detected, with a prevalence of 12%. The qacA/B, qacG, qacH, qacJ, and smr genes were identified at frequencies of 2%, 3%, 1%, 4.5%, and 5%, respectively. The highest MIC level was identified in the surface sample, which carried the qacG gene, at a concentration of 6.25 μg mL−1. The study's results highlight the potential risks associated with disinfectant resistance in food establishments. To prevent the transfer of disinfectant resistance genes, which have become a global risk, it is imperative that the rules of disinfectant usage are observed rigorously and that scientific research in this field is diversified.

Surfaces environmental monitoring of SARS-CoV-2: Loop mediated isothermal amplification (LAMP) and droplet digital PCR (ddPCR) in comparison with standard Reverse-Transcription quantitative polymerase chain reaction (RT-qPCR) techniques.

The persistence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) on substrates, and the impact of fomites on Coronavirus Disease 19 (COVID-19) transmission, is until now, widely discussed. Consequently, further investigations are required for a correct risk assessment in high-risk facilities such as hospitals, healthcare facilities (HCFs), and long-term care facilities (LTCFs). Therefore, appropriate surveillance and disinfection programs represent the best approach to guarantee the safety of these communities. This study proposes an environmental SARS-CoV-2 surfaces routine monitoring approach in HCF and communities' settings, to provide rapid and effective evaluation of surface hygienic conditions and the effectiveness of applied sanitization measures. Surfaces samples (n = 118) were collected using the SRK® kit (Copan Italia) from 2020 to 2023. Three molecular techniques were compared: Reverse Transcription Loop mediated isothermal AMPlification (RT-LAMP, Enbiotech), Reverse-Transcription quantitative polymerase chain reaction (RT-qPCR) (RT-qPCR, Seegene) and droplet digital PCR (ddPCR, Bio-Rad). For ddPCR, two RNA extraction methods were compared: TRIzol LS (Invitrogen) versus QIAmp Viral Mini kit (QIAGEN), showing how the latter is more suitable for surfaces. Regarding the quantitative ddPCR results, the ROC analysis allowed to reduce the manufacturer cut-off for droplets number (from 3 to 1) for the positive samples. Moreover, a new cut-off for the viral RNA copies' number/μL for each target (N1 and N2) on environmental monitoring was fixed at 2,82. The results obtained using the QIAmp kit, suggested that the N2 target is more stable in the environment and could be most suitable for the virus environmental detection. The percentage of positive samples was similar among the techniques (26% for RT-LAMP, 36% for ddPCR and 23% for RT-qPCR). Using RT-qPCR as reference method, a sensitivity (SE) of 30% for RT-LAMP and 41% for ddPCR was observed. By contrast, specificity (SP) was higher for RT-LAMP (75%) respect to ddPCR (66%). Comparing the faster RT-LAMP with the sensitive ddPCR the 26% and 74% of SE and SP for RT-LAMP, were reported. The low sensitivity for RT-LAMP and ddPCR could be explained with the use of clinical rather than environmental kits, other than the changing in the virus prevalence during the sampling campaign. Although the RT-LAMP requires improvements in term of SE and SP, this research presents an innovative environmental monitoring and prevention method for SARS-CoV-2, that could be extended to other pathogens that are under environmental surveillance.

Comparative Study of Sampling Technique, Surface Type, and DNA Quantity in Touch DNA: A Systematic Review

Touch DNA analysis has become increasingly important in forensic investigations. This systematic review aims to compare the effectiveness of various sampling techniques on different surface types and examine the concentration of DNA obtained. Following PRISMA guidelines, relevant studies were identified through PubMed, Scopus, and Web of Science databases. Data were extracted using NVivo and synthesized using a narrative approach, while study quality was assessed using the Mixed Methods Appraisal Tool (MMAT). Swabbing, particularly double swabbing, was the most common technique. However, tape lifting was more effective on porous/uneven surfaces, and wet-vacuum sampling outperformed double swabbing on brick. DNA concentrations varied (0.002−0.707 ng/μL) based on surface type and sampling method. Findings provide guidance for forensic practitioners in selecting optimal sampling techniques, refining DNA extraction protocols, and interpreting results. Nevertheless, methodological heterogeneity and laboratory focus limit generalizability. This review offers a comprehensive understanding of factors influencing touch DNA analysis success. Future research should focus on larger, standardized studies, novel sampling techniques, and advanced DNA analysis methods to address challenges associated with degraded or limited touch DNA samples. Continued research is crucial for enhancing the reliability and applicability of touch DNA evidence in forensic investigations.

TUNA-EBSD-CL correlative multi-microscopy study, on the example of Cu(In,Ga)S2 solar cell absorber.

Multi-microscopy offers significant benefits to the understanding of complex materials behaviour by providing complementary information from different properties. However, some characterisations may strongly influence other measurements in the same workflow. To acquire reliable and valid datasets, optimising multi-microscopy procedure is necessary. In present work, we studied the influence of the measurement order on the quality of multi-microscopy datasets. Multi-microscopy incorporating tunnelling current AFM (TUNA), electron backscatter diffraction (EBSD), and cathodoluminescence (CL) on a polycrystalline solar cell absorber, Cu(In,Ga)S2 (CIGS), is used as an example. The investigation revealed potential characterisation-induced contaminations, such as surface oxidation and hydrocarbon layer coating, of the sample surface. Their subsequent influence on the measurement results of following correlation techniques was examined. To optimise the dataset quality, multi-microscopy should be carried out in TUNA-EBSD-CL order, from the most to the least surface sensitive techniques. With the optimised multi-microscopy measurement order on a CIGS absorber, we directly correlated the local changes in electrical and opto-electronic properties with the microstructure of grain boundaries (GBs). The described methodology may also provide insightful concepts for applying other AFM-SEM-based multi-microscopy on different semiconductor materials.

Investigation on enhancing surface characteristics of UNS S32760 super duplex stainless steel weldment through optimized multiple shot peening technique

Mechanical property and corrosion resistance of TIG welded UNS S32760 super duplex stainless steel were studied in the present work. The sample surfaces were peened using bigger steel balls with higher intensity followed by another two stages of peening using smaller steel/glass balls at a lower intensity. Six different multiple shot peening parameters were applied onto the weld bead identified by SP1 through SP6. The microstructure and mechanical property of the weld bead was assessed through surface morphology, surface roughness, residual stress measurement, X-ray diffraction. Potentiodynamic polarization studies were carried out in 3.5% NaCl solution to understand the corrosion behavior. In general, it was found that the use of glass beads in the last stage of shot peening resulted in superior mechanical properties and corrosion resistance compared to peening using steel balls in all the three stages. Among the different treatments, SP2 parameter demonstrated superior microhardness (381.4 HV) and high residual stress (-880 MPa and -986.8 MPa in ferrite and austenite phase, respectively). Relatively higher domain size and lower microstrain along with low surface roughness of 1.25 µm (Ra) was responsible for the lowest corrosion rate (0.021mpy) in the SP2 treated weld bead.

Photon-stimulated desorption from laser-etched vacuum structural materials of accelerators

Abstract The electron multipacting (EM) and the electron cloud (e-cloud) can have detrimental impact on the operation of the high energy or high current intensity particle accelerators. The enhanced performance of new generation particle accelerators has necessitated the development of advanced structural materials and vacuum systems. The EM and e-cloud effect have emerged as significant challenges which cannot be ignored during the design and construction of these advanced accelerators. Laser-etching technique represents a promising approach for the suppression of secondary electron emission from materials, which can lower the secondary electron yield (SEY) of the structural materials to below 1. Nevertheless, the deployment of laser-etching technique in the next generation of large particle accelerators requires a comprehensive investigation into its vacuum performance. In this work, a photo-stimulated desorption (PSD) experimental beamline was constructed on the Hefei Light Source II. The PSD yields of the structural materials (oxygen-free copper, chrome zirconium copper, stainless steel, and aluminum alloy) with and without laser-etching of the vacuum chambers were tested at normal incidence using the throughput method. The main gases desorbed from all sample surfaces are H2, CO, CO2, CH4, and H2O. The initial PSD yield of laser-etched material is higher than that of unetched material. However, the PSD yield of the laser-etched material decreases at a faster rate, and after a certain photon dose, the PSD yield of the laser-etched material is in the same order of magnitude as that of the unetched material.

Multifunctional Surface Enhanced Raman Scattering Substrate Fe 3O4 @AgNPs@MIL-101 for Pretreatment and Rapid Detection of Pesticide Residues on the Surface of Fruit Peels.

A multifunctional surface-enhanced Raman scattering substrate Fe3O4@AgNPs@MIL-101 was prepared. Rapid SERS detection of pesticide residues was realized by direct pre-enrichment and separation on the peel surface. MIL-101 has an ortho-octahedral framework and large pore size, which endowed Fe3O4@AgNPs@MIL-101 with the ability to rapidly adsorb and separate positively charged targets. The introduction of tannic acid realized the insitu growth of AgNPs on the backbone, to modulate the electromagnetic enhancement. Pesticide molecules were adsorbed onto the surface of AgNPs mediated by central S atoms, accompanied by the interaction between pesticide molecules and AgNPs, the corresponding SERS signals of different pesticides were observed. Together with the introduction of magnetic coating Fe3O4, the molecules were enriched in the hotspot and separated to further enhance the SERS performance. Magnet instead of centrifugation was used to simultaneously perform surface extraction and sample separation for a noninvasive, rapid, immediate, and portable assay. The method was accomplished in measurement of thiram and thiabendazole on apple and tangerine epidermis, and the limits of detection (LODs) were 20 ng/cm2 and 4 μg/cm2, respectively. The recovery was reasonable, and it showed that the procedure is valuable for the rapid and nondestructive surface analysis of residual chemicals.

Influence of Sample Surface Oil on the Accuracy of Space Charge Measurement in Oil-Paper

Influence of Sample Surface Oil on the Accuracy of Space Charge Measurement in Oil-Paper

Thermo-oxidative degradation behavior of vulcanized butadiene rubber under thermal recycling conditions

Thermo-oxidative reclamation of tire rubber has been proven to be an energy-efficient method for upcycling end-of-life tire. As one of the key components, the complicated oxidative degradation behavior of butadiene rubber (BR) has significantly hindered the reclamation efficiency of tire rubber. This study investigated the thermo-oxidative degradation behavior of vulcanized BR in the temperature range (180-240°C) typically used for reclamation. The influence of oxygen diffusion on the degradation evolution of vulcanized BR was investigated using stacked sheet samples, by characterization of their chemical structure, network structure and mechanical properties during the degradation processes. The chemical structure changes indicated that increased surface oxidation led to more pronounced heterogeneous oxidative distribution within the stack. The different layers exhibited distinct degradation changes due to the competition among chain scission and recombination of rubber network structures in degraded BR. The depth profiles monitored by atomic force microscopy (AFM) observed a high-degree oxidized layer with newly crosslinked structures formed at the stacked sample surface, which was the main cause leading to the heterogeneous oxidative degradation. Additionally, the degradation degree of vulcanized BR was analyzed across different temperatures, with the highest degree of degradation was achieved at 210°C in 20 min.

Effects of Chemical Pretreatments of Wood Cellulose Nanofibrils on Protein Adsorption and Biological Outcomes.

Wood-based nanocellulose is emerging as a promising nanomaterial in the field of tissue engineering due to its unique properties and versatile applications. Previously, we used TEMPO-mediated oxidation (TO) and carboxymethylation (CM) as chemical pretreatments prior to mechanical fibrillation of wood-based cellulose nanofibrils (CNFs) to produce scaffolds with different surface chemistries. The aim of the current study was to evaluate the effects of these chemical pretreatments on serum protein adsorption on 2D and 3D configurations of TO-CNF and CM-CNF and then to investigate their effects on cell adhesion, spreading, inflammatory mediator production in vitro, and the development of foreign body reaction (FBR) in vivo. Mass spectrometry analysis revealed that the surface chemistry played a key role in determining the proteomic profile and significantly influenced the behavior of periodontal ligament fibroblasts and osteoblast-like cells (Saos-2). The surface of TO-CNF 2D samples showed the highest protein adsorption followed by TO-CNF 3D samples. CM-CNF 2D samples adsorbed a higher number of proteins than their 3D counterparts. None of the CNF scaffolds showed toxicity in vitro or in vivo. However, carboxymethylation pretreatment negatively affected the adhesion, morphology, and spreading of both cell types. Although the CNF materials displayed clear differences in surface chemistry and proteomic profiles, both triggered the same foreign body response after being subcutaneously implanted in rats for 90 days. This observation highlights that the degradation rate of CNF scaffolds plays a central role in maintaining the foreign body response in vivo. It is imperative to comprehend the impact of chemical pretreatments of CNFs on protein adsorption and their interaction with diverse host cell types prior to the investigation of potential modifications. This knowledge is indispensable for the advancement of CNFs in regenerative applications within tissue engineering.

P-253. Impact of Restroom Disinfecting/Cleaning Frequency and Product Selection on Risk of Infection

Abstract Background Restrooms are associated with transmission of bacterial and viral illnesses. Disinfecting pathogen-contaminated surfaces represents an intervention for reducing transmission risk. This study assessed whether cleaning/disinfecting frequency affects bacterial pathogen contamination in American patient rooms, long term care facilities and households with ≥ four occupants. Methods During the control phase, toilet surfaces (toilet bowl, water, and rim) were cleaned using a 9.5% w/w hydrochloric acid product only. During the intervention phase, multiple restroom surfaces (vanity/sink, toilet surfaces, floor, doorknob including toilet bowl) were cleaned/disinfected with disinfecting/cleaning products selected for the specific surfaces. Surface samples were collected and tested for heterotrophic and coliform bacteria after 1, 2, 3, or 7 days, with sampling being randomized during the week. The ratio of E. coli to norovirus in feces from an infected person was then used to perform a quantitative microbial risk assessment. Results The greatest numbers of bacteria were recovered on surfaces after three days. The largest reduction in bacterial recovery occurred during a three-day (∼twice-a-week) cleaning cycle, resulting in statistically significant reductions in recovery of heterotrophic bacteria (P = 0.00898) and Escherichia coli (P = 0.01). Conclusion Quantitative microbial risk assessments of commonly touched surfaces suggests that risk of infection by norovirus (highly contagious, excreted in high numbers, low human infectious dose) may be reduced by 91.5% using a three-day (twice-a-week) restroom cleaning/disinfection cycle. Disclosures Charles P. Gerba, PhD, Rickitt Benckiser: Grant/Research Support

P-258. A Longitudinal Study on the Impact of Sink Interventions on Environmental Bioburden and Patient Infections within Two Intensive Care Units at an Academic Hospital

Abstract Background Patient room sinks are frequently identified as potential sources for hospital-associated infections (HAIs), but there are no clear recommendations for interventions to reduce sink-related pathogenic bioburden. We conducted one of the first longitudinal crossover trials to assess the impact of practical sink interventions in an academic hospital.Figure 1.Contamination levels in patient room sink p-trap and tap water between units over time.Black lines represent samples with CFU/mL above the limit of detection. Methods We conducted a 4-phase randomized crossover trial in a medical ICU (MICU) and burn ICU (BICU). Each phase was 8 weeks with a 2-week washout between phases: drain covers, point-of-use filters, both, or no intervention on patient room sinks by unit. Environmental samples from tap water, p-trap water, air, and swabs of the sink basin and adjacent surface were collected every 2 weeks from 5 patient room sinks per unit. Colony-forming units (CFU)/mL of non-tuberculous mycobacteria (NTM), carbapenem-resistant Enterobacterales (CRE), multidrug-resistant Enterobacterales (MDRE), and Stenotrophomonas maltophilia were calculated following MALDI-TOF speciation. Patient HAI results were also recorded. Results Without filters, 68.7% (68/99) of tap water samples were positive, compared to 2.2% (2/90) with filters (p< 0.05). P-trap samples were highly variable with high bioburden and no clear time trends at the room or unit level (Figure 1). Positive air and surface samples rarely occurred but were most common in the drain cover phase (12/135). Within rooms, environmental samples were primarily positive before patient clinical isolates of the same species (7/8). Tap water samples across both units were primarily positive for NTM (71/189) yet no study-room-associated NTM infections were identified. Conclusion We identified that sinks, particularly p-traps, present a consistent source of pathogenic bioburden with fluctuating populations yet rarely contributed to surface/air contamination with organisms of interest in ICU patient rooms. Neither intervention impacted p-trap colonization (CFU/mL). We found that point-of-use filters consistently and effectively removed NTM from tap water. Drain covers were not found to be a useful intervention for reducing surface bioburden. Future research on decolonizing pathogenic bacteria from patient room p-traps is needed. Disclosures Becky A. Smith, MD, UpToDate: royalties

P-1146. Environmental Surfaces in Healthy Households as Reservoirs of Extended-Spectrum Cephalosporin-Resistant Enterobacterales in the Community

Abstract Background Community-acquired extended-spectrum cephalosporin resistant (ESCr)-Enterobacterales (E) are increasing in healthy populations, yet the sources of acquisition are unknown. We assessed household (HH) environmental surface samples (HS) in St. Louis, MO, to identify the surfaces most frequently contaminated with ESCr-E and the associated mechanisms of antibiotic resistance (AR). Figure 1. Enterobacterales within households. Methods From 139 HHs, samples from 21 HS and inguinal fold (IF) samples of healthy adults and children were cultured for bacteria. Families were recruited from outpatient pediatric settings. Bacterial identification and antibiotic susceptibility testing were conducted (Vitek®2, bioMérieux). Molecular characterization of ESCr-E was performed by PCR detection of beta-lactamase (bla) and plasmid-mediated quinolone resistance (PMQR) genes. Whole genome sequencing (WGS) was performed on select HH with > 1 colonized HS to evaluate for genetic relatedness, plasmids, and AR genes. A HH cluster was defined as < 15 single nucleotide polymorphism differences between 2 isolates. Figure 2. ESCR Enterobacterales by genera Results Of 581 IF and 2801 HS, the majority harbored bacteria (IF, 97-100% and HS, 79-100%) and gram-negative bacteria, (IF, 72-80% and HS, 75-87%). IF colonization with Enterobacterales was ∼23% and ranged from 7-60% on HS; The most common ESCr-E genera were Enterobacter (79%), Pantoea (10%), and Klebsiella (7%). ESCr-E were found in 2% of IF. HS most notably colonized with ESCr-E were the kitchen sink faucet (9%), oven door handle (4%), sofa (4%), bathroom sink faucet (3%) and bed sheets (3%), (Figures 1-3). ESBL-E were recovered from ∼2% of HHs. MDR-E (> 3 antibiotic classes) were found in 4% of HHs. WGS of 20 E. cloacae from 4 HHs revealed within HH clusters (Figure 4). Of interest, we found that among E. cloacae, 10/20 (50%) contained AR plasmids (ex. IncFI, IncFII, IncX5, IncHI2, Col440I); bla, other AR (ex. PMQR, aminoglycoside, sulfa, fosfomycin) and virulence genes were detected in E. cloacae in all HHs. We also found related E. cloacae strains in 2 HHs (ST108), indicating local strains circulating potentially related to a common exposure. Figure 3. AR Enterobacterales by surface. Conclusion ESCr-E are present in healthy household environments. Future directions will be to identify candidate clinical and epidemiological features linked with ESCr-E HH colonization. Figure 4. Genetic relatedness among household Enterobacter cloacae Disclosures Ahmed Babiker, MBBS, Beckman Coulter Inc.: Advisor/Consultant

P-2350. Respiratory Virus Detection among Children, Teachers, and Touch Surfaces in Childcare Centres: Preliminary Results from the DISeases TrANsmission in ChildcarE (DISTANCE) Cohort Study (2022–2024)

Abstract Background Childcare centres are commonly regarded as high-risk settings for respiratory virus transmission. To understand transmission risks within childcare centres, we conducted a prospective cohort study that collected data on respiratory infections in children and teaching staff, contact behaviours of children, and detection of respiratory viruses on touch surfaces (Figure 1).Figure 1.Schematic figure showing data collection and follow-up of the study. Methods We reported updated preliminary findings based on data collected from two childcare centres in Wuxi and Nanjing, China between September 26th, 2022, and January 22nd, 2024. Weekly throat swabs were collected from 211 children and 21 teachers. 56 touch surfaces, such as desks, door knobs, and faucets, were sampled on the same day from childcare centres (Table 1). Both respiratory and surface swab samples were tested by multiplex PCR for eight respiratory viruses.Table 1.Basic characteristics of the study and Positive cases of virus among children and teachers (estimate per 1000 person-weeks, 95% CI) Results 6886 respiratory specimens and 1868 touch surface samples were collected and tested over the reporting period. Respiratory viruses were most detected among children (7.41%, 447/6032), followed by teachers (4.10%, 35/854) and touch surfaces (2.09%, 39/1868). The top four viruses detected among all children were rhinovirus, influenza A virus, RSV, and PIV (Figure 2). Specifically, rhinovirus prevailed mostly in the Nanjing site (60.11 per 1000 person-weeks, 95% CI: 48.69–73.41), while influenza A dominated in the Wuxi site (23.00 per 1000 person-weeks, 18.75–27.92). Teachers had lower viral infections than children except for influenza A, where rates were comparable: teachers (16.39 per 1000 person-weeks, 8.96–27.51) and children (18.24 per 1000 person-weeks, 14.99–21.98). For a given week, influenza A detection was correlated between students and teachers (Spearman correlation coefficient r =0.55) at the Wuxi and Nanjing sites (Table 2). However, for SARS-COV-2, there was a higher correlation between touch surfaces and individuals (children: r = 0.67; teacher: r = 0.82), than between children and teachers in Wuxi.Figure 2.Comparison of incidence/detection rate among children, teachers and touch surfaces in two childcare centres. Conclusion Children in childcare centres face higher risks of respiratory viral infections than teachers. There is synchrony in detecting respiratory viruses among teachers, students and touch surfaces, indicating the varied contribution of each component to respiratory virus transmission in childcare centres.Table 2.Correlation coefficients of respiratory virus detection in Nanjing Disclosures You Li, Pfizer: Advisor/Consultant