Results for “TEM data” — Page 25

DOE OSTI2014

EBSD and TEM Characterization of High Burn-up Mixed Oxide Fuel

Understanding and studying the irradiation behavior of high burn-up oxide fuel is critical to licensing of future fast breeder reactors. Advancements in experimental techniques and equipment are allowing for new insights into previously irradiated samples. In this work dual column focused ion beam (FIB)/scanning electron microscope (SEM) was utilized to prepared transmission electron microscope samples from mixed oxide fuel with a burn-up of 6.7% FIMA. Utilizing the FIB/SEM for preparation resulted in samples with a dose rate of <0.5 mRem/h compared to approximately 1.1 R/h for a traditionally prepared TEM sample. The TEM analysis showed that the sample taken from the cooler rim region of the fuel pellet had approximately 2.5x higher dislocation density than that of the sample taken from the mid-radius due to the lower irradiation temperature of the rim. The dual column FIB/SEM was additionally used to prepared and serially slice approximately 25 um cubes. High quality electron back scatter diffraction (EBSD) were collected from the face at each step, showing, for the first time, the ability to obtain EBSD data from high activity irradiated fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2013

Synthesis and structure of high-quality films of copper polyphthalocyanine – 2D conductive polymer

Graphical abstract: - Highlights: • 2D polymers show a big promise for science and technology. • We develop a new procedure for the direct synthesis of copper polyphthalocyanine. • We obtain reliable experimental data on the CuPPC structure. • With the support of quantum chemical calculations we describe electronic structure of CuPPC. - Abstract: Copper polyphthalocyanine (CuPPC), a 2D conjugated polymer, is a promising material for electronics and photovoltaics, but its applications were hindered by a poor processability. We propose an experimental approach, by which thin films of CuPPC, can be directly synthesized in a chemical vapor deposition (CVD) set-up at mild temperature (420 °C). High polymerization degree and high crystallinity of the films were confirmed by TEM, FTIR and UV–vis studies. From XRD and TEM electron diffraction, we conclude that the polymer has AA layer stacking with the inter-layer distance of 0.32 nm. The assignment of X-ray and TEM diffraction patterns was based on quantum-chemical calculations. Based on the latter, we also discuss electronic structure and conclude that CuPPC is rather a semi-metal than semi-conductor.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Effect of Solvent Composition on Non-DLVO Forces and Oriented Attachment of Zinc Oxide Nanoparticles

Oriented attachment (OA) occurs when nanoparticles in solution align their crystallographic axes prior to colliding and subsequently fuse into single crystals. Traditional colloidal theories such as DLVO provide a framework for evaluating OA but fail to capture key particle interactions due to the atomistic details of both the crystal structure and the interfacial solution structure. Using zinc oxide as a model system, we investigated the effect of the solvent on short-ranged and long-ranged particle interactions and the resulting OA mechanism. In situ TEM imaging showed that ZnO nanocrystals in toluene undergo long-range attraction comparable to 1kT at separations of 10 nm and 3kT near particle contact. These observations were rationalized by considering non-DLVO interactions, namely dipole-dipole forces and torques between the polar ZnO nanocrystals. Langevin dynamics simulations showed stronger interactions in toluene compared to methanol solvents, consistent with the experimental results. Concurrently, we performed atomic force microscopy measurements using ZnO-coated probes for the short-ranged interaction. Our data provided valuable insights into another type of non-DLVO interaction, namely the repulsive solvation force. Specifically, the solvation force was stronger in water compared to ethanol and methanol, due to the stronger hydrogen bonding and denser packing of water molecules at the interface. In conclusion, our results highlight the importance of non-DLVO forces in a general framework for understanding and predicting particle aggregation and attachment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Manufacturing Supply Chain Development for Modular Solar-Thermochemical Conversion Platform [Abstract]

We will develop a tunable pulsed electron source capable of generating variable intensity highly-focused electron pulses at high repetition rates. Specifically, we need to demonstrate a high-speed variable electron gun capable of generating a variable intensity electron pulse containing between 102 and 105 electrons with an accelerating voltage of 1kV focused into a spot size <100nm in diameter at with a pulse rate >10MHz (with path to 300MHz). This combined performance cannot be achieved by commercially available electron sources. The primary technology path selected for this work will be to use a photocathode approach, where an easily modulated UV laser is used to stimulate electron emission. The approach utilizes the advances made in the development of the Dynamic TEM (DTEM), though this project will be simpler in that the pulse intensity is lower and there is no requirement for coherency. Alternate paths, including using a traditional electron beam modulated using a v-shaped slit and electrostatically deflecting the beam to adjust intensity; will also be considered for future capabilities. The electron source will then be used generate optically stimulated luminescence (OSL) in lithium fluoride (LiF) substrates to demonstrate the potential for OSL to serve as a basis technology for next generation data storage systems.

42 ENGINEERING↗

DOE OSTI2022

Nanoscale trace-element zoning in pyrite framboids and implications for paleoproxy applications

Pyrite framboids (spherical masses of nanoscale pyrite) are among the earliest textures of pyrite to form in sediments. It has been proposed that their trace-element (TE) contents can be used to track the TE composition of the water column in which they formed. However, it is not clear how these TEs are associated with the framboidal pyrite grains. For instance, it is important to know whether they are incorporated uniformly or are enriched in different regions of the framboid. Here, we used high-resolution scanning transmission electron microscopy to identify chemical zoning within pyrite framboids. We found that initial, nanoscale pyrite euhedral crystals, which make up the volumetric majority of the framboids, are covered/infilled by later pyrite that templates on the earlier pyrite. Further, this later pyrite is enriched in TEs, suggesting that many TEs are incorporated in pyrite relatively late (during early diagenesis; not in the water column). This observation suggests that although chemical analyses of pyrite framboids may provide ocean-water chemistry trends through time, the details are complex. Specifically, the TEs found in pyrite may be linked to adsorption onto organic matter, detrital material, and authigenic minerals such as Fe- and Mn-oxide phases followed by desorption in the sediments or release via dissolution and incorporation into pyrite as overgrowths on the initial nanoscale euhedral crystals that make up framboids. While the use of pyrite chemistry to understand past ocean conditions remains promising, and even diagenetic additions may not preclude the utility of pyrite for reconstructing ancient ocean conditions, care must be taken in interpretations because the end concentration may be influenced by diagenesis.

58 GEOSCIENCES↗

DOE OSTI2015

Compression Algorithm Analysis of In-Situ (S)TEM Video: Towards Automatic Event Detection and Characterization

Precise analysis of both (S)TEM images and video are time and labor intensive processes. As an example, determining when crystal growth and shrinkage occurs during the dynamic process of Li dendrite deposition and stripping involves manually scanning through each frame in the video to extract a specific set of frames/images. For large numbers of images, this process can be very time consuming, so a fast and accurate automated method is desirable. Given this need, we developed software that uses analysis of video compression statistics for detecting and characterizing events in large data sets. This software works by converting the data into a series of images which it compresses into an MPEG-2 video using the open source “avconv” utility [1]. The software does not use the video itself, but rather analyzes the video statistics from the first pass of the video encoding that avconv records in the log file. This file contains statistics for each frame of the video including the frame quality, intra-texture and predicted texture bits, forward and backward motion vector resolution, among others. In all, avconv records 15 statistics for each frame. By combining different statistics, we have been able to detect events in various types of data. We have developed an interactive tool for exploring the data and the statistics that aids the analyst in selecting useful statistics for each analysis. Going forward, an algorithm for detecting and possibly describing events automatically can be written based on statistic(s) for each data type.

algorithm analysis↗

DOE OSTI2024

FFTF HT9 Cladding Microstructure Characterization

The sodium-cooled fast reactor (SFR) is a promising candidate for next generation nuclear reactors, operating at extreme conditions which include high temperatures (>500?C core outlet temperature) and significant neutron damage. High-Cr martensitic HT9 steel is an excellent candidate for SFR cladding and duct material due to its compatibility with liquid sodium, good thermal conductivity, resistance to void swelling, and strong creep rupture strength [1-4].However, the harsh in-core environment of SFRs can cause complex microstructural changes and mechanical property degradation in HT-9. Ensuring the safe use of HT9 cladding for metallic fuel requires both a thorough understanding of its mechanical response to microstructure evolution as well as reliable microstructure-sensitive modeling predictions. Microstructure-sensitive modeling of high temperature creep behavior in HT9 cladding for SFR applications currently lack experimental data to model the phenomena accurately. To fill this need, methods to perform microstructural characterization have been developed and performed on HT9.

36 MATERIALS SCIENCE↗

NASA NTRS2003

Characterization of the Effects of Precursor Mineralogy on Hematite Spectra: Application to Martian Hematite Mineralization

The Thermal Emission Spectrometer (TES) instrument aboard Mars Global Surveyor discovered several isolated deposits of gray, crystalline hematite in Sinus Meridiani, Aram Chaos, and Valles Marineris. A variety of formation mechanisms has been proposed for the martian hematite deposits, including aqueous and nonaqueous processes. Comparison of the average Sinus Meridiani hematite spectrum measured by TES to laboratory emissivity spectra for a variety of naturally occurring hematites shows small but potentially important differences. In particular, the emissivity minimum at 300 and 445/cm in the Sinus Meridiani (SM) spectrum is displaced 10-25/cm to lower frequencies compared to some natural hematite samples. In addition, these bands in the TES data are narrower than the broad bands seen in many natural hematite spectra. These differences may imply that the natural variability of hematite spectra has not been fully characterized, especially with respect to the reaction pathway (precursor mineralogy and temperature of hematite formation) and crystal morphology. Here, we describe the thermal infrared spectral characteristics of several series of synthetic hematite samples derived by direct precipitation, dehydroxylation of fine-grained goethite and the oxidation of magnetite. Several natural hematite sample spectra are also presented for comparison. Transmission electron microscopy (TEM) and Mossbauer spectral analyses of selected samples were performed in order to help determine the causes of the changes seen in the infrared spectra.

Glotch, Timothy D.↗

DOE OSTI2023

Facile hermetic TEM grid preparation for molecular imaging of hydrated biological samples at room temperature

Abstract Although structures of vitrified supramolecular complexes have been determined at near-atomic resolution, elucidating in situ molecular structure in living cells remains a challenge. Here, we report a straightforward liquid cell technique, originally developed for real-time visualization of dynamics at a liquid-gas interface using transmission electron microscopy, to image wet biological samples. Due to the scattering effects from the liquid phase, the micrographs display an amplitude contrast comparable to that observed in negatively stained samples. We succeed in resolving subunits within the protein complex GroEL imaged in a buffer solution at room temperature. Additionally, we capture various stages of virus cell entry, a process for which only sparse structural data exists due to their transient nature. To scrutinize the morphological details further, we used individual particle electron tomography for 3D reconstruction of each virus. These findings showcase this approach potential as an efficient, cost-effective complement to other microscopy technique in addressing biological questions at the molecular level.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2018

High temperature irradiation induced creep in Ag nanopillars measured via in situ transmission electron microscopy

Irradiation induced creep (IIC) rates are measured in compression on Ag nanopillar (square) beams in the sink-limited regime. The IIC rate increases linearly with stress at lower stresses, i.e. below ≈2/3 the high temperature yield stress and parabolically with pillar width, L, for L less than ≈300 nm. Here, the data are obtained by combining in situ transmission electron imaging with simultaneous ion irradiation, laser heating, and nanopillar compression. Results in the larger width regime are consistent with prior literature.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Small-Scale Mechanical Testing of UO{sub 2}

The mechanical properties of UO{sub 2} fuel are of great importance to the nuclear engineering community for modeling of fuel performance during operation and accident scenarios. Data on the deformation of single crystals at room and elevated temperature can help these efforts by informing multiscale models. Small-scale testing techniques like micro-cantilever bending and nano-indentation have the ability to measure mechanical properties at the right length scale for this, while allowing the observation of the deformation of the material. In our work we perform micro-cantilever testing of UO{sub 2} at room temperature and nano-indentation testing up to 500 deg. C, as well as in-situ TEM micro-cantilever testing.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2017

Nanoporous Boron Nitride as Exceptionally Thermally Stable Adsorbent: Role in Efficient Separation of Light Hydrocarbons

Here in this work, nanoporous boron nitride sample was synthesized with a Brunauer–Emmett–Teller (BET) surface area of 1360 m 2 /g and particle size 5–7 μm. The boron nitride was characterized with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy (TEM and SEM). Thermogravimetric analysis (TGA) under nitrogen and air and subsequent analysis with XPS and XRD suggested that its structure is stable in air up to 800 °C and in nitrogen up to 1050 °C, which is higher than most of the common adsorbents reported so far. Nitrogen and hydrocarbon adsorption at 298 K and pressure up to 1 bar suggested that all hydrocarbon adsorption amounts were higher than that of nitrogen and the adsorbed amount of hydrocarbon increases with an increase in its molecular weight. The kinetics of adsorption data suggested that adsorption becomes slower with the increase in molecular weight of hydrocarbons. The equilibrium data suggested that that boron nitride is selective to paraffins in a paraffin–olefin mixture and hence may act as an “olefin generator”. The ideal adsorbed solution theory (IAST)-based selectivity for CH 4 /N 2 , C 2 H 6 /CH 4 , and C 3 H 8 /C 3 H 6 was very high and probably higher than the majority of adsorbents reported in the literature. IAST-based calculations were also employed to simulate the binary mixture adsorption data for the gas pairs of CH 4 /N 2 , C 2 H 6 /CH 4 , C 2 H 6 /C 2 H 4 , and C 3 H 8 /C 3 H 6 . Lastly, a simple mathematical model was employed to simulate the breakthrough behavior of the above-mentioned four gas pairs in a dynamic column experiment. The overall results suggest that nanoporous boron nitride can be used as a potential adsorbent for light hydrocarbon separation.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Welding investigation of a wrought FeMnAl steel for armor application

A new wrought FeMnAl steel contains high Mn content and high Al content. This steel has high strength. When it is compared to conventional steels with the similar strength, its density is lower. FeMnAl steels can be used in armor vehicle manufacturing, in which welding is a common practice to join the steel plates together. The welding of FeMnAl steels has not been sufficiently studied before. Here, this work studied the weldability and weld microstructure of an FeMnAl steel and provided useful data for the welding practice of FeMnAl steels. The influences of weld filler metals and shielding gases were studied, using single-pass bead-on-plate gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) two processes. The optimal filler metals and shielding gases have been determined to achieve the better weldability. Autogenous GTAW and electron beam welding were also conducted. Cracks were found in the HAZ in the GMAW welds and electron beam welds. Fewer or no cracks were found in the HAZ of GTAW welds. SEM, SEM/EDX, TEM, TEM/EDX, and EBSD were used to analyze the grain boundaries in the HAZ and the cracks. The grain boundaries of FeMnAl base metal are mostly high angle grain boundaries (HAGBs), which attract impurity and solute atoms and cause intergranular cracking. The proposed cracking mechanisms are liquation cracking and ductility-dip cracking. It was found that GTAW provides much better weldability for the FeMnAl steel than GMAW and EBW.

FeMnAl steel↗

DOE OSTI2015

Resonant spin tunneling in randomly oriented nanospheres of Mn 12 acetate

We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn₁₂ acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn₁₂ acetate crystal in the field parallel to the easy axis.Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for a single crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by re-analyzing the old data on a powdered sample of non-oriented micron-size crystals of Mn₁₂ acetate. In conclusion, our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Effect of pressure on the structural properties of Li[Li{sub 0.1}Ni{sub 0.35}Mn{sub 0.55}]O{sub 2}

Li-rich cathode material Li[Li{sub 0.1}Ni{sub 0.35}Mn{sub 0.55}]O{sub 2} was synthesized by a sol-gel method. The morphology and a-NaFeO{sub 2} type structure of the material at ambient conditions were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The high-pressure behavior of the material was studied at pressure up to 19.7 GPa by using angle dispersive synchrotron X-ray powder diffraction (ADXD). The studies affirmed that the a-NaFeO{sub 2} type structure existed up to at least 19.7 GPa. Rietveld refinement analysis indicated that the c/a lattice parameter ratio decreased and the Li-O bond length shrunk with the increasing pressure, however, the Li{sup +}/Ni{sup 2+} ions exchange increased under elevated pressure. The pressure-volume data of the material were fitted to the third-order Birch-Murnaghan equation of state and bulk modulus obtained upon compression from the fitting was 117 (1) GPa.

36 MATERIALS SCIENCE↗

NASA NTRSDate not supplied

A Gene Expression and Histologic Approach to Study Production and Outflow of Cerebrospinal Fluid in Hindlimb Suspended Rats

INTRODUCTION: The Spaceflight Associated Neuro-ocular Syndrome (SANS) is thought to be associated with weightlessness-induced cephalad fluid shift, possibly associated with a chronic elevation of intracranial pressure (ICP) during long-duration ISS missions. Changes in cerebrospinal fluid (CSF) dynamics and cranial compliance might be involved in the ICP increase. It is not known whether CSF production and/or outflow are altered in microgravity, but changes at the molecular and cellular level in the structures that produce and regulate the transcellular and paracellular secretion and reabsorption of CSF may be relevant. In this study, we used the rat hindlimb suspension (HS) model to examine the relationship between intracranial pressure (ICP) and the cellular responses to the prolonged change in body posture elicited specifically in the choroid plexus (CP). This was evaluated by transcriptomics, histopathology and ultrastructure of the CP and arachnoid villi (AV). METHODS: ICP was measured by telemetry. The morphology, ultrastructure, and gene expression profile of the CP was examined using male 9-month-old Long Evans rats subjected to HS for 14 and 90 days. A subset of animals completing 90-day HS returned to normal posture for 14 and 90 additional days of recovery. All HS rats had age-matched cage controls maintained in normal posture. A group of animals was maintained in conditions of 1% CO2 throughout the entire protocol. The rat brains were carefully removed and preserved for various analyses, including transmission electron microscopy (TEM), immunohistochemical analysis of specific targets involved in CSF regulation, and RNA sequencing analysis of laser capture micro-dissected CP tissue from the lateral ventricles. SUMMARY OF RESULTS: The ICP record was limited, which impacted any conclusions derived from the results. However, the ICP of rats in the CO2-enriched atmosphere appeared increased compared to those in a normal air composition. HS of rats resulted in an altered transcriptomics profile in the choroid plexus compared to animals maintained at normal posture. This was observed during both the HS period and during normal posture recovery period following 90 days of suspension. The greatest number of differentially expressed genes was observed at 90 days HS. Elevated CO2 also led to a different transcriptomics profile in the CP. The histology and ultrastructure results should be considered preliminary due to the limited number of samples. Examination of the CP by TEM showed blood vessel congestion and microvilli swelling in the CP, as well as some subpial and periventricular gliosis, but no associations were observed with treatment. There was no evidence of a reduced clearance of b-amyloid in the periventricular, perivascular and subpial regions of the brain in HS animals versus those in normal posture. Immunohistochemical staining of aquaporin 4, showed the localization to the subpial region and ependyma with increased immunoreactivity in the brains of CO2 exposed rats. This work was supported by awards NNX15AW48G to S.Z. Animal tissue and live data was provided under a tissue/data sharing agreement with Dr. Charles Fuller, UC Davis.

S B Zanello↗

NASA NTRSDate not supplied

A Gene Expression and Histologic Approach to Study Production and Outflow of Cerebrospinal Fluid in Hindlimb Suspended RATS

INTRODUCTION: The Spaceflight Associated Neuro-ocular Syndrome (SANS) is thought to be associated with weightlessness-induced cephalad fluid shift, possibly associated with a chronic elevation of intracranial pressure (ICP) during long-duration ISS missions. Changes in cerebrospinal fluid (CSF) dynamics and cranial compliance might be involved in the ICP increase. It is not known whether CSF production and/or outflow are altered in microgravity, but changes at the molecular and cellular level in the structures that produce and regulate the transcellular and paracellular secretion and reabsorption of CSF may be relevant. In this study, we used the rat hindlimb suspension (HS) model to examine the relationship between intracranial pressure (ICP) and the cellular responses to the prolonged change in body posture elicited specifically in the choroid plexus (CP). This was evaluated by transcriptomics, histopathology and ultrastructure of the CP and arachnoid villi (AV). METHODS: ICP was measured by telemetry. The morphology, ultrastructure, and gene expression profile of the CP was examined using male 9-month-old Long Evans rats subjected to HS for 14 and 90 days. A subset of animals completing 90-day HS returned to normal posture for 14 and 90 additional days of recovery. All HS rats had age-matched cage controls maintained in normal posture. A group of animals was maintained in conditions of 1% CO2 throughout the entire protocol. The rat brains were carefully removed and preserved for various analyses, including transmission electron microscopy (TEM), immunohistochemical analysis of specific targets involved in CSF regulation, and RNA sequencing analysis of laser capture micro-dissected CP tissue from the lateral ventricles. SUMMARY OF RESULTS: The ICP record was limited, which impacted any conclusions derived from the results. However, the ICP of rats in the CO2-enriched atmosphere appeared increased compared to those in a normal air composition. HS of rats resulted in an altered transcriptomics profile in the choroid plexus compared to animals maintained at normal posture. This was observed during both the HS period and during normal posture recovery period following 90 days of suspension. The greatest number of differentially expressed genes was observed at 90 days HS. Elevated CO2 also led to a different transcriptomics profile in the CP. The histology and ultrastructure results should be considered preliminary due to the limited number of samples. Examination of the CP by TEM showed blood vessel congestion and microvilli swelling in the CP, as well as some subpial and periventricular gliosis, but no associations were observed with treatment. There was no evidence of a reduced clearance of b-amyloid in the periventricular, perivascular and subpial regions of the brain in HS animals versus those in normal posture. Immunohistochemical staining of aquaporin 4, showed the localization to the subpial region and ependyma with increased immunoreactivity in the brains of CO2 exposed rats. This work was supported by awards NNX15AW48G to S.Z. Animal tissue and live data was provided under a tissue/data sharing agreement with Dr. Charles Fuller, UC Davis.

S B Zanello↗

DOE OSTI2022

Genetic Predictive Factors for Nonsusceptible Phenotypes and Multidrug Resistance in Expanded-Spectrum Cephalosporin-Resistant Uropathogenic Escherichia coli from a Multicenter Cohort: Insights into the Phenotypic and Genetic Basis of Coresistance

Antimicrobial resistance in urinary tract infections (UTIs) is a major public health concern. This study aims to characterize the phenotypic and genetic basis of multidrug resistance (MDR) among expanded-spectrum cephalosporin-resistant (ESCR) uropathogenic Escherichia coli (UPEC) causing UTIs in California patient populations. Between February and October 2019, 577 ESCR UPEC isolates were collected from patients at 6 clinical laboratory sites across California. Lineage and antibiotic resistance genes were determined by analysis of whole-genome sequence data. The lineages ST131, ST1193, ST648, and ST69 were predominant, representing 46%, 5.5%, 4.5%, and 4.5% of the collection, respectively. Overall, 527 (91%) isolates had an expanded-spectrum β-lactamase (ESBL) phenotype, with bla CTX-M-15 , bla CTX-M-27 , bla CTX-M-55 , and bla CTX-M-14 being the most prevalent ESBL genes. In the 50 non-ESBL phenotype isolates, 40 (62%) contained bla CMY-2 , which was the predominant plasmid-mediated AmpC (pAmpC) gene. Narrow-spectrum β-lactamases, bla TEM-1B and bla OXA-1 , were also found in 44.9% and 32.1% of isolates, respectively. Among ESCR UPEC isolates, isolates with an ESBL phenotype had a 1.7-times-greater likelihood of being MDR than non-ESBL phenotype isolates (P < 0.001). The cooccurrence of bla CTX-M-15 , bla OXA-1 , and aac(6')-Ib-cr within ESCR UPEC isolates was strongly correlated. Cooccurrence of bla CTX-M-15 , bla OXA-1 , and aac(6')-Ib-cr was associated with an increased risk of nonsusceptibility to piperacillin-tazobactam, cefepime, fluoroquinolones, and amikacin as well as MDR. Multivariate regression revealed the presence of bla CTX-M-55 , bla TEM-1B , and the ST131 genotype as predictors of MDR.

59 BASIC BIOLOGICAL SCIENCES↗