Antimicrobial resistance surveillance of Bacteroides fragilis isolated from blood cultures, Europe, 2022 (ReSuBacfrag).

BACKGROUND: Bacteroides fragilis is the most frequent cause of anaerobic bacteraemia. Although recent data suggest a rise in antimicrobial resistance (AMR) of this and other anaerobic bacteria, surveillance remains limited due to a lack of both data availability and comparability. However, a newly introduced standardised method for antimicrobial susceptibility testing (AST) of anaerobic bacteria has made larger scale surveillance possible for the first time. AIM: To investigate phenotypic AMR of Bacteroides fragilis isolates from bacteraemia across Europe in 2022. METHODS: In a multicentre approach, clinical microbiology laboratories in Europe were invited to contribute results of AST for Bacteroides fragilis blood culture isolates (including only the first isolate per patient and year). AST of a selection of four antibiotics was performed locally by participating laboratories in a prospective or retrospective manner, using the new EUCAST disc diffusion method on fastidious anaerobe agar (FAA-HB). RESULTS: A total of 16 European countries reported antimicrobial susceptibilities in 449 unique isolates of Bacteroides fragilis from blood cultures in 2022. Clindamycin demonstrated the highest resistance rates (20.9%, range 0 - 63.6%), followed by piperacillin-tazobactam (11.1%, 0 - 54.5%), meropenem (13.4%, 0 - 45.5%), and metronidazole (1.8%, 0 - 20.0%), all with wide variation between countries. CONCLUSION: Considering that the mean resistance rates across Europe were higher than expected for three of the four anti-anaerobic antibiotics under surveillance, both local AST of clinically relevant isolates of Bacteroides fragilis and continued surveillance on an international level is warranted.

De-epimerizing DyKAT of ß-lactones generated by isothiourea-catalysed enantioselective [2 + 2] cycloaddition.

An enantioselective isothiourea-catalysed [2 + 2] cycloaddition of C(1)-ammonium enolates with pyrazol-4,5-diones is used to construct spirocyclic ß-lactones in good yields, excellent enantioselectivity (99 : 1 er) but with modest diastereocontrol (typically 70 : 30 dr). Upon ring-opening with morpholine or alternative nucleophilic amines and alcohols ß-hydroxyamide and ß-hydroxyester products are generated with enhanced diastereocontrol (up to >95 : 5 dr). Control experiments show that stereoconvergence is observed in the ring-opening of diastereoisomeric ß-lactones, leading to a single product (>95 : 5 dr, >99 : 1 er). Mechanistic studies and DFT analysis indicate a substrate controlled Dynamic Kinetic Asymmetric Transformation (DyKAT) involving epimerisation at C(3) of the ß-lactone under the reaction conditions, coupled with a hydrogen bond-assisted nucleophilic addition to the Si-face of the ß-lactone and stereodetermining ring-opening. The scope and limitations of a one-pot protocol consisting of isothiourea-catalysed enantio-determining [2 + 2] cycloaddition followed by diastereo-determining ring-opening are subsequently developed. Variation within the anhydride ammonium enolate precursor, as well as N(1) and C(3) within the pyrazol-4,5-dione scaffold is demonstrated, giving a range of functionalised ß-hydroxyamides with high diastereo- and enantiocontrol (>20 examples, up to >95 : 5 dr and >99 : 1 er) via this DyKAT.

Dissociation of HNO3 in water revisited: experiment and theory.

Nitric acid dissociation in water is studied as a function of concentration, employing experimental techniques (1H NMR spectroscopy and calorimetry), quantum chemical methods (B3LYP and PBE functionals for molecular clusters) and molecular dynamics simulations (the PBE-D3 functional for solutions under periodic boundary conditions). The extent of dissociation, via proton transfer to a neighboring water molecule, as a function of concentration is studied computationally for molecular nitric acid clusters HNO3(H2O)x (x = 1-8), as well as periodic liquids (HNO3 mole fractions of 0.19 and 0.5, simulated at T = 300 K and 450 K). Despite the simple nature of these structural models, their computed and simulated average 1H chemical shifts compare well with the experimental measurements in this study. Finally, the measured and calculated chemical shifts have shown reasonable relationships with the enthalpy change upon mixing of this binary complex.

Understanding divergent substrate stereoselectivity in the isothiourea-catalysed conjugate addition of cyclic α-substituted ß-ketoesters to α,ß-unsaturated aryl esters.

The development of enantioselective synthetic methods capable of generating vicinal stereogenic centres, where one is tetrasubstituted (such as either an all-carbon quaternary centre or where one or more substituents are heteroatoms), is a recognised synthetic challenge. Herein, the enantioselective conjugate addition of a range of carbo- and heterocyclic α-substituted ß-ketoesters to α,ß-unsaturated aryl esters using the isothiourea HyperBTM as a Lewis base catalyst is demonstrated. Notably, divergent diastereoselectivity is observed through the use of either cyclopentanone-derived or indanone-derived substituted ß-ketoesters with both generating the desired stereodefined products with high selectivity (>95 : 5 dr, up to 99 : 1 er). The scope and limitations of these processes are demonstrated, alongside application on gram scale. The origin of the divergent substrate selectivity has been probed through the use of DFT-analysis, with preferential orientation driven by dual stabilising CH⋯O interactions. The importance of solvation with strongly polar transition-states is highlighted and the SMD solvation model is demonstrated to capture solvation effects reliably.

13C pNMR shifts of MOFs based on Cu(II)-paddlewheel dimers - DFT predictions for spin-1/2 defects.

We present DFT predictions (CAM-B3LYP/II level) for the paramagnetic Nuclear Magnetic Resonance (pNMR) spectra of small molecular models based on the Cu(II)-paddlewheel dimer motif that is present in metal-organic frameworks (MOFs, notably the HKUST and STAM families). We explore potential point defects with spin-1/2 discovered through electron paramagnetic resonance (EPR) experiments. We consider defects through substitution of one Cu(II) centre in the dimer with protons, or through one-electron reduction, affording a mixed-valence dimer. While most of the defects have predicted pNMR shifts at room temperature in the range of those for the non-defective MOFs, their detection and assignment should be possible based on their distinct temperature dependence.

Constrained Phosphine Chalcogenide Selenoethers Supported by peri-Substitution.

A series of phosphorus and selenium peri-substituted acenaphthene species with the phosphino group oxidized by O, S, and Se has been isolated and fully characterized, including by single-crystal X-ray diffraction. The P(V) and Se(II) systems showed fluxional behavior in solution due to the presence of two major rotamers, as evidenced with solution NMR spectroscopy. Using Variable-Temperature NMR (VT NMR) and supported by DFT (Density Functional Theory) calculations and solid-state NMR, the major rotamers in the solid and in solution were identified. All compounds showed a loss of the through-space JPSe coupling observed in the unoxidized P(III) and Se(II) systems due to the sequestration of the lone pair of the phosphine, which has been previously identified as the major contributor to the coupling pathway.

Phosphine and Selenoether peri-Substituted Acenaphthenes and Their Transition-Metal Complexes: Structural and NMR Investigations.

A series of peri-substituted acenaphthene-based phosphine selenoether bidentate ligands Acenap(iPr2P)(SeAr) (L1-L4, Acenap = acenaphthene-5,6-diyl, Ar = Ph, mesityl, 2,4,6-trisopropylphenyl and supermesityl) were prepared. The rigid acenaphthene framework induces a forced overlap of the phosphine and selenoether lone pairs, resulting in a large magnitude of through-space 4JPSe coupling, ranging from 452 to 545 Hz. These rigid ligands L1-L4 were used to prepare a series of selected late d-block metals, mercury, and borane complexes, which were characterized, including by multinuclear NMR and single-crystal X-ray diffraction. The Lewis acidic motifs (BH3, Mo(CO)4, Ag+, PdCl2, PtCl2, and HgCl2) bridge the two donor atoms (P and Se) in all but one case in the solid-state structures. Where the bridging motif contained NMR-active nuclei (11B, 107Ag, 109Ag, 195Pt, and 199Hg), JPM and JSeM couplings are observed directly, in addition to the altered JPSe in the respective NMR spectra. The solution NMR data are correlated with single-crystal diffraction data, and in the case of mercury(II) complexes, they are also correlated with the solid-state NMR data and coupling deformation density calculations. The latter indicate that the through-space interaction dominates in free L1, while in the L1HgCl2 complex, the main coupling pathway is via the metal atom and not through the carbon framework of the acenaphthene ring system.

Correction to "Manganese Catalyzed Dehydrogenative Synthesis of Urea Derivatives and Polyureas".

[This corrects the article DOI: 10.1021/acscatal.2c00850.].

Synthesis of Polyethyleneimines from the Manganese-Catalysed Coupling of Ethylene Glycol and Ethylenediamine.

Polyethyleneimines find many applications in products such as detergents, adhesives, cosmetics, and for processes such as tissue culture, gene therapy, and CO2 capture. The current state-of-the-art technology for the production of the branched polyethyleneimines involves aziridine feedstock which is a highly toxic, volatile and mutagenic chemical and raises significant concern to human health and environment. We report here a novel method for the synthesis of branched polyethyleneimine derivative from ethylene glycol and ethylenediamine which are much safer, environmentally benign, commercially available and potentially renewable feedstock. The polymerisation reaction is catalysed by a complex of an earth-abundant metal, manganese and liberates H2 O as the only by-product. Our mechanistic studies using a combination of DFT computation and experiment suggest that the reaction proceeds by the formation and subsequent hydrogenation of imine intermediates.

Towards Computational Modeling of Ligand Binding to the ILPR G-Quadruplex.

Using a combination of unconstrained and constrained molecular dynamics simulations, we have evaluated the binding affinities between two porphyrin derivatives (TMPyP4 and TEGPy) and the G-quadruplex (G4) of a DNA fragment modeling the insulin-linked polymorphic region (ILPR). Refining a well-established potential of mean force (PMF) approach to selections of constraints based on root-mean-square fluctuations results in an excellent agreement between the calculated and observed absolute free binding energy of TMPyP4. The binding affinity of IPLR-G4 toward TEGPy is predicted to be higher than that toward TMPyP4 by 2.5 kcal/mol, which can be traced back to stabilization provided by the polyether side chains of TMPyP4 that can nestle into the grooves of the quadruplex and form hydrogen bonds through the ether oxygen atoms. Because our refined methodology can be applied to large ligands with high flexibility, the present research opens an avenue for further ligand design in this important area.

Resolving colistin resistance and heteroresistance in Enterobacter species.

Species within the Enterobacter cloacae complex (ECC) include globally important nosocomial pathogens. A three-year study of ECC in Germany identified Enterobacter xiangfangensis as the most common species (65.5%) detected, a result replicated by examining a global pool of 3246 isolates. Antibiotic resistance profiling revealed widespread resistance and heteroresistance to the antibiotic colistin and detected the mobile colistin resistance (mcr)-9 gene in 19.2% of all isolates. We show that resistance and heteroresistance properties depend on the chromosomal arnBCADTEF gene cassette whose products catalyze transfer of L-Ara4N to lipid A. Using comparative genomics, mutational analysis, and quantitative lipid A profiling we demonstrate that intrinsic lipid A modification levels are genospecies-dependent and governed by allelic variations in phoPQ and mgrB, that encode a two-component sensor-activator system and specific inhibitor peptide. By generating phoPQ chimeras and combining them with mgrB alleles, we show that interactions at the pH-sensing interface of the sensory histidine kinase phoQ dictate arnBCADTEF expression levels. To minimize therapeutic failures, we developed an assay that accurately detects colistin resistance levels for any ECC isolate.

Outcomes of octogenarians and nonagenarians with Pseudomonas aeruginosa bacteremia: a multicenter retrospective study.

BACKGROUND: P. aeruginosa bacteremia is a common and severe infection carrying high mortality in older adults. We aimed to evaluate outcomes of P. aeruginosa bacteremia among old adults (≥ 80 years). METHODS: We included the 464/2394 (19%) older adults from a retrospective multinational (9 countries, 25 centers) cohort study of individuals hospitalized with P. aeruginosa bacteremia. Bivariate and multivariable logistic regression models were used to evaluate risk factors for 30-day mortality among older adults. RESULTS: Among 464 adults aged ≥ 80 years, the mean age was 84.61 (SD 3.98) years, and 274 (59%) were men. Compared to younger patients, ≥ 80 years adults had lower Charlson score; were less likely to have nosocomial acquisition; and more likely to have urinary source. Thirty-day mortality was 30%, versus 27% among patients 65-79 years (n = 894) and 25% among patients < 65 years (n = 1036). Multivariate analysis for predictors of mortality among patients ≥ 80 years, demonstrated higher SOFA score (odds ratio [OR] 1.36, 95% confidence interval [CI] 1.23-1.51, p < 0.001), corticosteroid therapy (OR 3.15, 95% CI: 1.24-8.01, p = 0.016) and hospital acquired P. aeruginosa bacteremia (OR 2.30, 95% CI: 1.33-3.98, p = 0.003) as predictors. Appropriate empirical therapy within 24 h, type of definitive anti-pseudomonal drug, and type of regimen (monotherapy or combination) were not associated with 30-day mortality. CONCLUSIONS: In older adults with P. aeruginosa bacteremia, background conditions, place of acquisition, and disease severity are associated with mortality, rather than the antimicrobial regimen. In this regard, preventive efforts and early diagnosis before organ failure develops might be beneficial for improving outcomes.

Rational Design of a Facially Coordinating P,N,N Ligand for Manganese-Catalysed Enantioselective Hydrogenation of Cyclic Ketones.

DFT calculations on the full catalytic cycle for manganese catalysed enantioselective hydrogenation of a selection of ketones have been carried out at the PBE0-D3PCM //RI-BP86PCM level. Mn complexes of an enantiomerically pure chiral P,N,N ligand have been found to be most reactive when adopting a facial coordination mode. The use of a new ligand with an ortho-substituted dimethylamino-pyridine motif has been calculated to completely transform the levels of enantioselectivity possible for the hydrogenation of cyclic ketones relative to the first-generation Mn catalysts. In silico evaluation of substrates has been used to identify those likely to be reduced with high enantiomer ratios (er), and others that would exhibit less selectivity; good agreements were then found in experiments. Various cyclic ketones and some acetophenone derivatives were hydrogenated with er's up to 99 : 1.

Electrochemical Activation Applied to Perovskite Titanate Fibers to Yield Supported Alloy Nanoparticles for Electrocatalytic Application.

Active bi-metallic nanoparticles are of key importance in catalysis and renewable energy. Here, the in situ formation of bi-metallic nanoparticles is investigated by exsolution on 200 nm diameter perovskite fibers. The B-site co-doped perovskite fibers display a high degree of exsolution, decorated with NiCo or Ni3 Fe bi-metallic nanoparticles with average diameter about 29 and 35 nm, respectively. The perovskite fibers are utilized as cathode materials in pure CO2 electrolysis cells due to their redox stability in the CO/CO2 atmosphere. After in situ electrochemical switching, the nanoparticles exsolved from the perovskite fiber demonstrate an enhanced performance in pure CO2 electrolysis. At 900 °C, the current density of solid oxide electrolysis cell (SOEC) with 200 µm YSZ electrolyte supported NiFe doped perovskite fiber anode reaches 0.75 Acm-2 at 1.6 V superior to the NiCo doped perovskite fiber anode (about 1.5 times) in pure CO2 . According to DFT calculations (PBE-D3 level) the superior CO2 conversion on NiFe compared to NiCo bi-metallic species is related to an enhanced driving force for C-O cleavage under formation of CO chemisorbed on the nanoparticle and a reduced binding energy of CO required to release this product.

Computational Insights into the Catalytic Mechanism of Is-PETase: An Enzyme Capable of Degrading Poly(ethylene) Terephthalate.

Is-PETase has become an enzyme of significant interest due to its ability to catalyse the degradation of polyethylene terephthalate (PET) at mesophilic temperatures. We performed hybrid quantum mechanics and molecular mechanics (QM/MM) at the DSD-PBEP86-D3/ma-def2-TZVP/CHARMM27//rev-PBE-D3/dev2-SVP/CHARMM level to calculate the energy profile for the degradation of a suitable PET model by this enzyme. Very low overall barriers are computed for serine protease-type hydrolysis steps (as low as 34.1 kJ mol-1 ). Spontaneous deprotonation of the final product, terephthalic acid, with a high computed driving force indicates that product release could be rate limiting.

Machine learning-based typing of Salmonella enterica O-serogroups by the Fourier-Transform Infrared (FTIR) Spectroscopy-based IR Biotyper system.

BACKGROUND: Salmonella enterica is among the major burdens for public health at global level. Typing of salmonellae below the species level is fundamental for different purposes, but traditional methods are expensive, technically demanding, and time-consuming, and therefore limited to reference centers. Fourier transform infrared (FTIR) spectroscopy is an alternative method for bacterial typing, successfully applied for classification at different infra-species levels. AIM: This study aimed to address the challenge of subtyping Salmonella enterica at O-serogroup level by using FTIR spectroscopy. We applied machine learning to develop a novel approach for S. enterica typing, using the FTIR-based IR Biotyper® system (IRBT; Bruker Daltonics GmbH & Co. KG, Germany). We investigated a multicentric collection of isolates, and we compared the novel approach with classical serotyping-based and molecular methods. METHODS: A total of 958 well characterized Salmonella isolates (25 serogroups, 138 serovars), collected in 11 different centers (in Europe and Japan), from clinical, environmental and food samples were included in this study and analyzed by IRBT. Infrared absorption spectra were acquired from water-ethanol bacterial suspensions, from culture isolates grown on seven different agar media. In the first part of the study, the discriminatory potential of the IRBT system was evaluated by comparison with reference typing method/s. In the second part of the study, the artificial intelligence capabilities of the IRBT software were applied to develop a classifier for Salmonella isolates at serogroup level. Different machine learning algorithms were investigated (artificial neural networks and support vector machine). A subset of 88 pre-characterized isolates (corresponding to 25 serogroups and 53 serovars) were included in the training set. The remaining 870 samples were used as validation set. The classifiers were evaluated in terms of accuracy, error rate and failed classification rate. RESULTS: The classifier that provided the highest accuracy in the cross-validation was selected to be tested with four external testing sets. Considering all the testing sites, accuracy ranged from 97.0% to 99.2% for non-selective media, and from 94.7% to 96.4% for selective media. CONCLUSIONS: The IRBT system proved to be a very promising, user-friendly, and cost-effective tool for Salmonella typing at serogroup level. The application of machine learning algorithms proved to enable a novel approach for typing, which relies on automated analysis and result interpretation, and it is therefore free of potential human biases. The system demonstrated a high robustness and adaptability to routine workflows, without the need of highly trained personnel, and proving to be suitable to be applied with isolates grown on different agar media, both selective and unselective. Further tests with currently circulating clinical, food and environmental isolates would be necessary before implementing it as a potentially stand-alone standard method for routine use.

Transmission of spin-polarization by π-orbitals: an approach to assessing its effect on NMR spin-spin coupling and EPR hyperfine structure.

A new approach to assessing the effect of the transmission of spin-polarization by π-orbitals (π-TSP) is presented. In order to switch off the π-TSP effect, we artificially average the α- and ß-densities of the valence π-orbitals when calculating the exchange-correlation contribution to the Fock matrix in the unrestricted Kohn-Sham framework. The π-TSP effect is then evaluated as the difference between the results obtained with switched-on and switched-off options. This approach is applied to estimate the π-TSP effect on the Fermi-contact contribution to spin-spin couplings and EPR hyperfine structure coupling constants. The π-TSP effect on the distribution of spin-density, spin-spin coupling pathways and pathways of EPR hyperfine couplings is demonstrated for benzene, naphthalene, 1,3,5,7,9-decapentaene and the 1,3,5,7,9-decapentaen-1-yl radical. The sign alternation of the spin-polarization transmitted by π-orbitals is explained in a theoretical framework based on perturbation theory. However, the delocalized nature of the π-system can interfere with the sign alternation in certain cases, two of which - the cyclobutadiene dication and the cyclooctatetraene dication - are examined, and an explanation for which is provided.

Isothiourea-Catalyzed Enantioselective Michael Addition of Malonates to α,ß-Unsaturated Aryl Esters.

An enantioselective Michael addition of malonates to α,ß-unsaturated para-nitrophenyl esters was achieved using the Lewis basic isothiourea HyperBTM, giving excellent levels of product enantioselectivity (up to >99:1 enantiomeric ratio) in good yields and with complete regioselectivity (>20:1 regioselectivity ratio) in the presence of alternative (phenyl ketone and ethyl ester) Michael acceptors. Density functional theory calculations indicate that N-acylation is rate-limiting. This constitutes a rare example of a highly enantioselective addition of simple, readily available malonates to α,ß-unsaturated esters.

Duration of Treatment for Pseudomonas aeruginosa Bacteremia: a Retrospective Study.

INTRODUCTION: There is no consensus regarding optimal duration of antibiotic therapy for Pseudomonas aeruginosa bacteremia. We aimed to evaluate the impact of short antibiotic course. METHODS: We present a retrospective multicenter study including patients with P. aeruginosa bacteremia during 2009-2015. We evaluated outcomes of patients treated with short (6-10 days) versus long (11-15 days) antibiotic courses. The primary outcome was a composite of 30-day mortality or bacteremia recurrence and/or persistence. Univariate and inverse probability treatment-weighted (IPTW) adjusted multivariate analysis for the primary outcome was performed. To avoid immortal time bias, the landmark method was used. RESULTS: We included 657 patients; 273 received a short antibiotic course and 384 a long course. There was no significant difference in baseline characteristics of patients. The composite primary outcome occurred in 61/384 patients in the long-treatment group (16%) versus 32/273 in the short-treatment group (12%) (p = 0.131). Mortality accounted for 41/384 (11%) versus 25/273 (9%) of cases, respectively. Length of hospital stay was significantly shorter in the short group [median 13 days, interquartile range (IQR) 9-21 days, versus median 15 days, IQR 11-26 days, p = 0.002]. Ten patients in the long group discontinued antibiotic therapy owing to adverse events, compared with none in the short group. On univariate and multivariate analyses, duration of therapy was not associated with the primary outcome. CONCLUSIONS: In this retrospective study, 6-10 days of antibiotic course for P. aeruginosa bacteremia were as effective as longer courses in terms of survival and recurrence. Shorter therapy was associated with reduced length of stay and less drug discontinuation.