RESUMO
Multidrug-resistant (MDR) Pseudomonas aeruginosa infections are a major clinical challenge. Many isolates are carbapenem resistant, which severely limits treatment options; thus, novel therapeutic combinations, such as imipenem-relebactam (IMI/REL), ceftazidime-avibactam (CAZ/AVI), ceftolozane-tazobactam (TOL/TAZO), and meropenem-vaborbactam (MEM/VAB) were developed. Here, we studied two extensively drug-resistant (XDR) P. aeruginosa isolates, collected in the United States and Mexico, that demonstrated resistance to IMI/REL. Whole-genome sequencing (WGS) showed that both isolates contained acquired GES ß-lactamases, intrinsic PDC and OXA ß-lactamases, and disruptions in the genes encoding the OprD porin, thereby inhibiting uptake of carbapenems. In one isolate (ST17), the entire C terminus of OprD deviated from the expected amino acid sequence after amino acid G388. In the other (ST309), the entire oprD gene was interrupted by an ISPa1328 insertion element after amino acid D43, rendering this porin nonfunctional. The poor inhibition by REL of the GES ß-lactamases (GES-2, -19, and -20; apparent Ki of 19 ± 2 µM, 23 ± 2 µM, and 21 ± 2 µM, respectively) within the isolates also contributed to the observed IMI/REL-resistant phenotype. Modeling of REL binding to the active site of GES-20 suggested that the acylated REL is positioned in an unstable conformation as a result of a constrained Ω-loop.
Assuntos
Infecções por Pseudomonas , Pseudomonas aeruginosa , Aminoácidos , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Compostos Azabicíclicos/farmacologia , Compostos Azabicíclicos/uso terapêutico , Combinação de Medicamentos , Humanos , Imipenem/farmacologia , Imipenem/uso terapêutico , Testes de Sensibilidade Microbiana , Porinas/genética , Infecções por Pseudomonas/tratamento farmacológico , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , Estados Unidos , beta-Lactamases/metabolismoRESUMO
Staphylococcus aureus is an opportunistic pathogen that causes a wide range of infections and food poisoning in humans with antibiotic resistance, specifically to methicillin, compounding the problem. Bacteriophages (phages) provide an alternative treatment strategy, but these only infect a limited number of circulating strains and may quickly become ineffective due to bacterial resistance. To overcome these obstacles, engineered phages have been proposed, but new methods are needed for the efficient transformation of large DNA molecules into S. aureus to "boot-up" (i.e., rescue) infectious phages. We presented a new, efficient, and reproducible DNA transformation method, NEST (non-electroporation Staphylococcus transformation), for S. aureus to boot-up purified phage genomic DNA (at least 150 kb in length) and whole yeast-assembled synthetic phage genomes. This method was a powerful new tool for the transformation of DNA in S. aureus and will enable the rapid development of engineered therapeutic phages and phage cocktails against Gram-positive pathogens. IMPORTANCE The continued emergence of antibiotic-resistant bacterial pathogens has heightened the urgency for alternative antibacterial strategies. Phages provide an alternative treatment strategy but are difficult to optimize. Synthetic biology approaches have been successfully used to construct and rescue genomes of model phages but only in a limited number of highly transformable host species. In this study, we used a new, reproducible, and efficient transformation method to reconstitute a functional nonmodel Siphophage from a constructed synthetic genome. This method will facilitate the engineering of Staphylococcus and Enterococcus phages for therapeutic applications and the engineering of Staphylococcus strains by enabling transformation of higher molecular weight DNA to introduce more complex modifications.
Assuntos
Fagos de Staphylococcus , Staphylococcus aureus , DNA Viral/genética , Humanos , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/virologia , Fagos de Staphylococcus/genética , Staphylococcus aureus/virologiaRESUMO
BACKGROUND: A complex cascade of genes, enzymes, and transcription factors regulates AmpC ß-lactamase overexpression. We investigated the network of AmpC ß-lactamase overexpression in Klebsiella aerogenes and identified the role of AmpG in resistance to ß-lactam agents, including cephalosporins and carbapenems. METHODS: A transposon mutant library was created for carbapenem-resistant K. aerogenes YMC2008-M09-943034 (KE-Y1) to screen for candidates with increased susceptibility to carbapenems, which identified the susceptible mutant derivatives KE-Y3 and KE-Y6. All the strains were subjected to highly contiguous de novo assemblies using PacBio sequencing to investigate the loss of resistance due to transposon insertion. Complementation and knock-out experiments using lambda Red-mediated homologous recombinase and CRISPR-Cas9 were performed to confirm the role of gene of interest. RESULTS: In-depth analysis of KE-Y3 and KE-Y6 revealed the insertion of a transposon at six positions in each strain, at which truncation of the AmpG permease gene was common in both. The disruption of the AmpG permease leads to carbapenem susceptibility, which was further confirmed by complementation. We generated an AmpG permease gene knockout using lambda Red-mediated recombineering in K. aerogenes KE-Y1 and a CRISPR-Cas9-mediated gene knockout in multidrug-resistant Klebsiella pneumoniae-YMC/2013/D to confer carbapenem susceptibility. CONCLUSIONS: These findings suggest that inhibition of the AmpG is a potential strategy to increase the efficacy of ß-lactam agents against Klebsiella aerogenes.
Assuntos
Proteínas de Bactérias/genética , Carbapenêmicos/farmacologia , Cefalosporinas/farmacologia , Proteínas de Membrana Transportadoras/genética , Resistência beta-Lactâmica/genética , beta-Lactamas/farmacologia , Sequência de Aminoácidos , Antibacterianos/farmacologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Sistemas CRISPR-Cas , Elementos de DNA Transponíveis , República Democrática Popular da Coreia , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Técnicas de Inativação de Genes , Humanos , Klebsiella pneumoniae/genética , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Testes de Sensibilidade Microbiana , Mutagênese , Alinhamento de Sequência , Resistência beta-Lactâmica/efeitos dos fármacosRESUMO
In an infection with an Enterobacter sp. isolate producing Klebsiella pneumoniae Carbapenemase-4 and New Delhi Metallo-ß-Lactamase-1 in the United States, recognition of the molecular basis of carbapenem resistance allowed for successful treatment by combining ceftazidime-avibactam and aztreonam. Antimicrobial synergy testing and therapeutic drug monitoring assessed treatment adequacy.
Assuntos
Bacteriemia , Infecções por Klebsiella , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Compostos Azabicíclicos/uso terapêutico , Aztreonam/uso terapêutico , Bacteriemia/tratamento farmacológico , Proteínas de Bactérias , Ceftazidima/uso terapêutico , Combinação de Medicamentos , Enterobacter , Humanos , Infecções por Klebsiella/tratamento farmacológico , Klebsiella pneumoniae/genética , Testes de Sensibilidade Microbiana , Estados Unidos , beta-Lactamases/genéticaRESUMO
Plazomicin was tested against 697 recently acquired carbapenem-resistant Klebsiella pneumoniae isolates from the Great Lakes region of the United States. Plazomicin MIC50 and MIC90 values were 0.25 and 1 mg/liter, respectively; 680 isolates (97.6%) were susceptible (MICs of ≤2 mg/liter), 9 (1.3%) intermediate (MICs of 4 mg/liter), and 8 (1.1%) resistant (MICs of >32 mg/liter). Resistance was associated with rmtF-, rmtB-, or armA-encoded 16S rRNA methyltransferases in all except 1 isolate.
Assuntos
Antibacterianos/farmacologia , Enterobacteriáceas Resistentes a Carbapenêmicos/efeitos dos fármacos , Klebsiella pneumoniae/efeitos dos fármacos , Metiltransferases/genética , Sisomicina/análogos & derivados , Adulto , Idoso , Proteínas de Bactérias/metabolismo , Farmacorresistência Bacteriana/genética , Feminino , Humanos , Klebsiella pneumoniae/genética , Klebsiella pneumoniae/isolamento & purificação , Masculino , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Sisomicina/farmacologia , Estados Unidos , beta-Lactamases/metabolismoRESUMO
Previously, by targeting penicillin-binding protein 3, Pseudomonas-derived cephalosporinase (PDC), and MurA with ceftazidime-avibactam-fosfomycin, antimicrobial susceptibility was restored among multidrug-resistant (MDR) Pseudomonas aeruginosa. Herein, ceftazidime-avibactam-fosfomycin combination therapy against MDR P. aeruginosa clinical isolate CL232 was further evaluated. Checkerboard susceptibility analysis revealed synergy between ceftazidime-avibactam and fosfomycin. Accordingly, the resistance elements present and expressed in P. aeruginosa were analyzed using whole-genome sequencing and transcriptome profiling. Mutations in genes that are known to contribute to ß-lactam resistance were identified. Moreover, expression of blaPDC, the mexAB-oprM efflux pump, and murA were upregulated. When fosfomycin was administered alone, the frequency of mutations conferring resistance was high; however, coadministration of fosfomycin with ceftazidime-avibactam yielded a lower frequency of resistance mutations. In a murine infection model using a high bacterial burden, ceftazidime-avibactam-fosfomycin significantly reduced the P. aeruginosa colony-forming units (CFUs), by approximately 2 and 5 logs, compared with stasis and in the vehicle-treated control, respectively. Administration of ceftazidime-avibactam and fosfomycin separately significantly increased CFUs, by approximately 3 logs and 1 log, respectively, compared with the number at stasis, and only reduced CFUs by approximately 1 log and 2 logs, respectively, compared with the number in the vehicle-treated control. Thus, the combination of ceftazidime-avibactam-fosfomycin was superior to either drug alone. By employing a "mechanism-based approach" to combination chemotherapy, we show that ceftazidime-avibactam-fosfomycin has the potential to offer infected patients with high bacterial burdens a therapeutic hope against infection with MDR P. aeruginosa that lack metallo-ß-lactamases.
Assuntos
Antibacterianos/administração & dosagem , Compostos Azabicíclicos/administração & dosagem , Ceftazidima/administração & dosagem , Farmacorresistência Bacteriana Múltipla , Fosfomicina/administração & dosagem , Infecções por Pseudomonas/tratamento farmacológico , Pseudomonas aeruginosa/efeitos dos fármacos , Animais , Combinação de Medicamentos , Sinergismo Farmacológico , Quimioterapia Combinada , Feminino , Humanos , Camundongos , Testes de Sensibilidade Microbiana , Mutação , Infecções por Pseudomonas/microbiologia , Células-TroncoRESUMO
BACKGROUND: Recent experimental evidence showed that lactobacilli could be used as potential therapeutic agents for hyperammonemia. However, lack of understanding on how lactobacilli reduce blood ammonia levels limits application of lactobacilli to treat hyperammonemia. RESULTS: We report the finished and annotated genome sequence of L. amylovorus JBD401 (GenBank accession no. CP012389). L. amylovorus JBD401 reducing blood ammonia levels dramatically was identified by high-throughput screening of several thousand probiotic strains both within and across Lactobacillus species in vitro. Administration of L. amylovorus JBD401 to hyperammonemia-induced mice reduced the blood ammonia levels of the mice to the normal range. Genome sequencing showed that L. amylovorus JBD401 had a circular chromosome of 1,946,267 bp with an average GC content of 38.13%. Comparative analysis of the L. amylovorus JBD401 genome with L. acidophilus and L. amylovorus strains showed that L. amylovorus JBD401 possessed genes for ammonia assimilation into various amino acids and polyamines Interestingly, the genome of L. amylovorus JBD401 contained unusually large number of various pseudogenes suggesting an active stage of evolution. CONCLUSIONS: L. amylovorus JBD401 has genes for assimilation of free ammonia into various amino acids and polyamines which results in removal of free ammonia in intestinal lumen to reduce the blood ammonia levels in the host. This work explains the mechanism of how probiotics reduce blood ammonia levels.
Assuntos
Amônia/sangue , Genoma Bacteriano , Lactobacillus/genética , Aminoácidos/metabolismo , Amônia/metabolismo , Animais , Proteínas de Bactérias/genética , Hibridização Genômica Comparativa , Evolução Molecular , Lactobacillus/metabolismo , Lactobacillus acidophilus/genética , Redes e Vias Metabólicas/genética , Camundongos , Ornitina Carbamoiltransferase/genética , Fosfotransferases (Aceptor do Grupo Carboxila)/genética , Poliaminas/metabolismoRESUMO
We identified the carbapenemase gene blaOXA-499, a variant of blaOXA-143, from a clinical isolate of Acinetobacter pittii for the first time. OXA-499 shared 93.1% amino acid identity with OXA-143, and the gene was located on the chromosome. By cloning the OXA-499-encoding gene into the pWH1266 vector and transforming it into susceptible Acinetobacter spp., we were able to show that OXA-499 confers resistance to carbapenems.
Assuntos
Infecções por Acinetobacter/tratamento farmacológico , Acinetobacter/genética , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Carbapenêmicos/farmacologia , Resistência beta-Lactâmica/genética , beta-Lactamases/genética , Acinetobacter/efeitos dos fármacos , Acinetobacter/isolamento & purificação , Infecções por Acinetobacter/microbiologia , Idoso , DNA Bacteriano/genética , Humanos , Masculino , Testes de Sensibilidade Microbiana , Análise de Sequência de DNARESUMO
Optical Coherence Tomography (OCT) is an emerging technique in the field of biomedical imaging, with applications in ophthalmology, dermatology, coronary imaging etc. OCT images usually suffer from a granular pattern, called speckle noise, which restricts the process of interpretation. Therefore the need for speckle noise reduction techniques is of high importance. To the best of our knowledge, use of Independent Component Analysis (ICA) techniques has never been explored for speckle reduction of OCT images. Here, a comparative study of several ICA techniques (InfoMax, JADE, FastICA and SOBI) is provided for noise reduction of retinal OCT images. Having multiple B-scans of the same location, the eye movements are compensated using a rigid registration technique. Then, different ICA techniques are applied to the aggregated set of B-scans for extracting the noise-free image. Signal-to-Noise-Ratio (SNR), Contrast-to-Noise-Ratio (CNR) and Equivalent-Number-of-Looks (ENL), as well as analysis on the computational complexity of the methods, are considered as metrics for comparison. The results show that use of ICA can be beneficial, especially in case of having fewer number of B-scans.
RESUMO
In recent years, antimicrobial resistance has become a major medical threat worldwide. Among these threats, the rapid increase in carbapenem-resistant Acinetobacter baumannii (CRAB) is a particularly challenging global issue in the health care setting. In this study, a novel lytic A. baumannii phage, ΒÏ-R3177, infecting carbapenem-resistant A. baumannii strains was isolated from sewage samples at a hospital. The morphology of the phage as assessed by transmission electron microscopy (TEM) indicated that it belongs to the family Siphoviridae within the order Caudovirales. It has a linear double-stranded DNA genome of 47,575 bp with a G+C content of 39.83%. Eighty open reading frames (ORFs) were predicted; however, only 14 ORFs were annotated as encoding functional proteins, while most of the ORFs encoded hypothetical proteins. Among the total ORFs of the phage genome, no toxin-related genes were detected. A bioinformatics analysis showed that the whole genome sequence of phage ΒÏ-R3177 exhibited 62% sequence similarity to that of Acinetobacter phage ΒÏ-B1252, but there was no homology seen with other phages. Physiological characteristics, such as one-step growth properties, pH and temperature stability, and host cell lysis activity showed this phage has high stability and lytic activity against host bacteria and therefore has potential applicability as an antibacterial agent to control pathogens in the hospital environment.
Assuntos
Acinetobacter baumannii/virologia , Bacteriófagos/genética , Bacteriófagos/isolamento & purificação , Genoma Viral , Siphoviridae/genética , Siphoviridae/isolamento & purificação , Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/enzimologia , Proteínas de Bactérias/metabolismo , Bacteriófagos/classificação , Bacteriófagos/fisiologia , Sequência de Bases , Carbapenêmicos/farmacologia , Farmacorresistência Bacteriana , Dados de Sequência Molecular , Fases de Leitura Aberta , Filogenia , Siphoviridae/classificação , Siphoviridae/fisiologia , beta-Lactamases/metabolismoRESUMO
BACKGROUND: Increasing numbers of cyber attacks threaten us personally and professionally. Cyber crimes include obtaining sensitive information (medical or financial) but may extend to organising heinous crimes including murders and aggravated sexual assaults. A major vector of cyber crimes is brute force attacks on secured shell servers. AIM OF STUDY: This research highlights the prevalence of the intensity of brute force attacks on secured shell servers via quali-quantitative analysis of cyber attacks. METHODOLOGY: The brute force attacks were recorded over a period of 20 days with the help of logs taken from five dedicated servers installed in a production environment. RESULTS: There were a minimum of 6470 and maximum of 22,715 attacks on a server per day. The total number of attacks on all the servers during the study period was 1,065,920. The brute force attacks were mainly targeted at the service network accounts. CONCLUSION: Growth of the field of cyber forensics is the optimal solution to prevent the malicious use of internet services and the commissioning of crimes by this means.
RESUMO
Background: Skin secretions of toads are widely used in medicine all over the world for their antiviral, anti-infective, and cardiotonic properties. Because these secretions are mostly employed to combat blood parasite infection, it is important to understand their potential toxic effects on human erythrocytes. Therefore, the objective of the current investigation was to elucidate the effects of Duttaphrynus melanostictus (Schneider) skin extracts on the physiology of human erythrocytes. Methods: Toads captured from their natural habitat were separated into three groups according to their body size. Hydroalcoholic extracts of toad skin were prepared by reflux heating. These extracts were then evaluated for their hemolytic and hemoglobin denaturation potential. The effects of the extracts on cytosolic and membrane-bound enzymes of human erythrocytes were assessed. Results: The hemolysis and hemoglobin denaturation caused by these extracts correlated positively with the respective toad sizes. Extracts from medium and large toads led to increased osmotic fragility even at near iso-osmotic concentrations. Biochemical analysis of hemolysate showed that the treatment induced a shift of metabolic flux toward the glutathione pathway. Analysis of membrane-bound enzymes revealed a significant decrease in the activity of Na+/K+ ATPase and acetylcholinesterase. SDS-PAGE analysis of the erythrocyte membrane did not show the band of tropomodulin for the cells treated with 1000 ðg/ml extract from large toads. Conclusions: In conclusion, the present study demonstrates that the toxicity of toad skin secretions aggravates with the size of the animal and interferes with the physiology of human erythrocytes, leading to their membrane disruption and rapid lysis.
RESUMO
Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) present significant healthcare challenges due to limited treatment options. Bacteriophage (phage) therapy offers potential as an alternative treatment. However, the high host specificity of phages poses challenges for their therapeutic application. To broaden the phage spectrum, laboratory-based phage training using the Appelmans protocol was employed in this study. As a result, the protocol successfully expanded the host range of a phage cocktail targeting CRAB. Further analysis revealed that the expanded host range phages isolated from the output cocktail were identified as recombinant derivatives originating from prophages induced from encountered bacterial strains. These findings provide valuable genetic insights into the protocol's mechanism when applied to phages infecting A. baumannii strains that have never been investigated before. However, it is noteworthy that the expanded host range phages obtained from this protocol exhibited limited stability, raising concerns about their suitability for therapeutic purposes.
Assuntos
Bacteriófagos , Prófagos , Prófagos/genética , Bacteriófagos/genética , Recombinação Genética , Especificidade de HospedeiroRESUMO
Advancements in widefield infrared spectromicroscopy have recently been demonstrated following the commissioning of IRENI (InfraRed ENvironmental Imaging), a Fourier Transform infrared (FTIR) chemical imaging beamline at the Synchrotron Radiation Center. The present study demonstrates the effects of magnification, spatial oversampling, spectral pre-processing and deconvolution, focusing on the intracellular detection and distribution of an exogenous metal tris-carbonyl derivative 1 in a single MDA-MB-231 breast cancer cell. We demonstrate here that spatial oversampling for synchrotron-based infrared imaging is critical to obtain accurate diffraction-limited images at all wavelengths simultaneously. Resolution criteria and results from raw and deconvoluted images for two Schwarzschild objectives (36×, NA 0.5 and 74×, NA 0.65) are compared to each other and to prior reports for raster-scanned, confocal microscopes. The resolution of the imaging data can be improved by deconvolving the instrumental broadening that is determined with the measured PSFs, which is implemented with GPU programming architecture for fast hyperspectral processing. High definition, rapidly acquired, FTIR chemical images of respective spectral signatures of the cell 1 and shows that 1 is localized next to the phosphate- and Amide-rich regions, in agreement with previous infrared and luminescence studies. The infrared image contrast, localization and definition are improved after applying proven spectral pre-processing (principal component analysis based noise reduction and RMie scattering correction algorithms) to individual pixel spectra in the hyperspectral cube.
Assuntos
Líquido Intracelular/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Linhagem Celular Tumoral , Feminino , HumanosRESUMO
We use the Cellular Potts Model (CPM) to study the contact angle (CA) hysteresis in multiphase (solid-liquid-vapour) systems. We simulate a droplet over the tilted patterned surface, and a bubble placed under the surface immersed in liquid. The difference between bubbles and droplets was discussed through their CA hysteresis. Dependency of CA hysteresis on the surface structure and other parameters was also investigated. This analysis allows decoupling of the 1D (pinning of the triple line) and 2D (adhesion hysteresis in the contact area) effects and provides new insight into the nature of CA hysteresis.
RESUMO
Diabetes is known as a multifactorial disease. The treatment of diabetes is complicated due to its inherent pathophysiological factors related to the disease. One of the complications of diabetes is postprandial hyperglycemia. Glucosidase inhibitors, particularly ?-amylase inhibitors can help manage postprandial hyperglycemia. The low molecular weight inhibitor of ? -amylases called PAMI (peptide amylase inhibitor) inhibits the ? -amylase. In this study we cloned this amylase blocker PAMI in Lactococcus lactis. Using this Lactococcus lactis expressing the PAMI, we prepared yogurt and fed it to diabetic mice models. There was decrease in the blood glucose level after 20 days of oral administration of the yogurt. This product be used as a biodrug in maintaining the blood glucose level in diabetic patients.
Assuntos
Amilases/antagonistas & inibidores , Produtos Biológicos/metabolismo , Inibidores Enzimáticos/metabolismo , Hipoglicemiantes/metabolismo , Lactococcus lactis/genética , Oligopeptídeos/genética , Animais , Glicemia/análise , Clonagem Molecular , Diabetes Mellitus Experimental/dietoterapia , Inibidores Enzimáticos/farmacologia , Regulação Bacteriana da Expressão Gênica , Engenharia Genética , Vetores Genéticos/genética , Lactococcus lactis/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Oligopeptídeos/metabolismo , Oligopeptídeos/farmacologia , Transformação Bacteriana , Resultado do Tratamento , Iogurte/microbiologiaRESUMO
ABSTRACT: This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was â¼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision.
Assuntos
Enterococcus faecium , Prunus dulcis , Contagem de Colônia Microbiana , Farinha , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Temperatura Alta , Pós , Salmonella/fisiologia , Triticum , Água/análiseRESUMO
High-fidelity patient-specific modeling of cardiovascular flows and hemodynamics is challenging. Direct blood flow measurement inside the body with in-vivo measurement modalities such as 4D flow magnetic resonance imaging (4D flow MRI) suffer from low resolution and acquisition noise. In-vitro experimental modeling and patient-specific computational fluid dynamics (CFD) models are subject to uncertainty in patient-specific boundary conditions and model parameters. Furthermore, collecting blood flow data in the near-wall region (e.g., wall shear stress) with experimental measurement modalities poses additional challenges. In this study, a computationally efficient data assimilation method called reduced-order modeling Kalman filter (ROM-KF) was proposed, which combined a sequential Kalman filter with reduced-order modeling using a linear model provided by dynamic mode decomposition (DMD). The goal of ROM-KF was to overcome low resolution and noise in experimental and uncertainty in CFD modeling of cardiovascular flows. The accuracy of the method was assessed with 1D Womersley flow, 2D idealized aneurysm, and 3D patient-specific cerebral aneurysm models. Synthetic experimental data were used to enable direct quantification of errors using benchmark datasets. The accuracy of ROM-KF in reconstructing near-wall hemodynamics was assessed by applying the method to problems where near-wall blood flow data were missing in the experimental dataset. The ROM-KF method provided blood flow data that were more accurate than the computational and synthetic experimental datasets and improved near-wall hemodynamics quantification.
Assuntos
Aneurisma Intracraniano , Modelos Cardiovasculares , Velocidade do Fluxo Sanguíneo , Hemodinâmica , Humanos , Hidrodinâmica , Modelagem Computacional Específica para o PacienteRESUMO
Evolution of multi-drug resistant bacteria has led to worldwide research to better understand the various resistance mechanisms in these strains. Every year, novel information on carbapenem resistance and its mechanisms is being discovered. In this study, radiation-mediated mutagenesis was used to transform a carbapenem-resistant Klebsiella pneumoniae strain to a carbapenem-susceptible bacterium. Through this process, we proved three conditions of loss of the OmpK35 and the OmpK36 genes and acquisition of blaCMY-10 worked together to produce carbapenem resistance in K. pneumoniae. Loss of only one of the porins did not evoke carbapenem resistance. This is the first report on the essential contribution of these three components of carbapenem resistance in K. pneumoniae.
Assuntos
Antibacterianos/farmacologia , Carbapenêmicos/farmacologia , Farmacorresistência Bacteriana , Infecções por Klebsiella/metabolismo , Infecções por Klebsiella/microbiologia , Klebsiella pneumoniae/genética , Klebsiella pneumoniae/efeitos da radiação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Humanos , Klebsiella pneumoniae/efeitos dos fármacos , Mutagênese/efeitos da radiação , Porinas/genética , Porinas/metabolismo , Radiação , beta-Lactamases/genética , beta-Lactamases/metabolismoRESUMO
PURPOSE: Variations in the vessel radius of segmented surfaces of intracranial aneurysms significantly influence the fluid velocities given by computer simulations. It is important to generate models that capture the effect of these variations in order to have a better interpretation of the numerically predicted hemodynamics. Also, it is highly relevant to develop methods that combine experimental observations with uncertainty modeling to get a closer approximation to the blood flow behavior. METHODS: This work applies polynomial chaos expansion to model the effect of geometric uncertainties on the simulated fluid velocities of intracranial aneurysms. The radius of the vessel is defined as the uncertainty variable. Proper orthogonal decomposition is applied to characterize the solution space of fluid velocities. Next, a process of projecting the 4D-Flow MRI velocities on the basis vectors followed by coefficient mapping using generalized dynamic mode decomposition enables the merging of 4D-Flow MRI with the uncertainty propagated fluid velocities. RESULTS: Polynomial chaos expansion propagates the fluid velocities with an error of 2% in velocity magnitude relative to computer simulations. Also, the bifurcation region (or impingement location) shows a standard deviation of 0.17 m/s (since an available reported variance in the vessel radius is adopted to model the uncertainty, the expected standard deviation may be different). Numerical phantom experiments indicate that the proposed approach reconstructs the fluid velocities with 0.3% relative error in presence of geometric uncertainties. CONCLUSION: Polynomial chaos expansion is an effective approach to propagate the effect of the uncertainty variable in the blood flow velocities of intracranial aneurysms. Merging 4D-Flow MRI and uncertainty propagated fluid velocities leads to more realistic flow trends relative to ignoring the uncertainty in the vessel radius.