Glycopeptide resistance in Enterococcus spp. and coagulase-negative staphylococci from hospitalised patients in Germany: occurrence, characteristics and dalbavancin susceptibility

Objectives: The aim of this study was to evaluate the occurrence of glycopeptide resistance in enterococci and coagulase-negative staphylococci (CoNS) and to determine the susceptibilities of the identified glycopeptide-resistant isolates to dalbavancin. Methods: Twenty-two medical laboratories participated in the study conducted in 2016/17 by the Paul-Ehrlich-Society for Chemotherapy. Each laboratory was asked to collect 30 Enterococcus spp. (limited to Enterococcus faecalis and Enterococcus faecium) and 30 CoNS isolates consecutively from hospitalised patients with a proven or suspected infection. Results: A total of 1285 isolates were collected, comprising 364 E. faecalis, 291 E. faecium and 630 CoNS. No E. faecalis isolates (0%) but 76 E. faecium isolates (26.1%) were vancomycin-resistant, of which 21 showed the VanA type and 55 the VanB type. The proportion of vancomycin-resistant strains among E. faecium isolates from patients in intensive care units (21.6%) was significantly lower than that from patients on regular wards (30.5%). Among the CoNS, 67 isolates (10.6%) were teicoplanin-resistant but none were vancomycin-resistant, with resistance only detected in Staphylococcus epidermidis (12.2%), Staphylococcus haemolyticus (17.9%) and Staphylococcus hominis (13.2%). Dalbavancin at ≤0.25 mg/L inhibited all VanB-type enterococci and 95.5% of teicoplanin-resistant CoNS. Conclusion: The level of glycopeptide resistance in E. faecalis remains very low in Germany but achieved 26% in E. faecium and was >10% in CoNS. Dalbavancin appears to be a feasible option for treating infections caused by VanB-type vancomycin-resistant E. faecium and teicoplanin-resistant CoNS.Peer Reviewe

Conformational heterogeneity of the Roc domains in C. tepidum Roc-COR and implications for human LRRK2 Parkinson mutations

Ras of complex proteins (Roc) is a Ras-like GTP binding domain that always occurs in tandem with the C-terminal of Roc (COR) domain, and is found in bacteria, plants and animals. Recently, it has been shown that Roco proteins belong to the family of G-proteins activated by nucleotide-dependent dimerization (GADs). We investigated the RocCOR tandem from the bacteria Chlorobium tepidum with site-directed spin labeling and pulse EPR distance measurements to follow conformational changes during the Roco G-protein cycle. Our results confirm that the COR domains are a stable dimerization device serving as a scaffold for the Roc domains, that in contrast are structurally heterogeneous and dynamic entities. Contrary to other GAD proteins, we observed only minor structural alterations upon binding and hydrolysis of GTP, indicating significant mechanistic variations within this protein class. Mutations in the most prominent member of the Roco family of proteins, leucine-rich repeat kinase 2 (LRRK2), are the most frequent cause of late-onset Parkinson's disease (PD). Using a stable recombinant LRRK2 Roc-COR-Kinase fragment we obtained detailed kinetic data for the G-protein cycle. Our data confirmed that dimerization is essential for efficient GTP hydrolysis, and PD mutations in the Roc domain result in decreased GTPase activity. Previous data have shown that these LRRK2 PD-mutations are located in the interface between Roc and COR. Importantly, analogous mutations in the conserved C. tepidum RocCOR interface significantly influence the structure and nucleotide-induced conformational changes of the Roc domains

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

Ten novel hydrogen-bonding catalysts based on open-chain P-V-amides of BINOL and chinchona alkaloids as well as three catalysts based on rigid cis-P-V-cyclodiphosphazane amides of N-1,N-1-dimethylcyclohexane-1,2-diamine have been developed. Employed in the asymmetric Michael addition of 2-hydroxynaphthoquinone to beta-nitrostyrene, the open-chain 9-epi-aminochinchona-based phosphorus amides show a high catalytic activity with almost quantitative yields of up to 98% and enantiomeric excesses of up to 51%. The cyclodiphosphazane catalysts show the same high activity and give improved enantiomeric excesses of up to 75%, thus representing the first successful application of a cyclodiphosphazane in enantioselective organocatalysis. DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane P-V-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by the catalyst

Asymmetric Michael Additions of 4-Hydroxycoumarin to beta-Nitrostyrenes with Chiral, Bifunctional Hydrogen-Bonding Catalysts

Enantioselective Michael additions of 4-hydroxycoumarin to beta-nitrostyrenes are catalyzed by different chiral, bifunctional hydrogen-bonding catalysts, based on thiourea and squaramide motifs. The scope of the catalysis is tested by employing a series of substituted beta-nitrostyrenes as well as different solvents. The 3,5-bis(trifiuoromethyl)phenyl- and quinine-substituted squaramide catalyst is shown to be the most selective catalyst, resulting in 78% yield and 81% ee. Computational analyses of transition structures with different binding modes show that the most favored transition structure exhibits squaramide (NH)(2), binding to an oxygen atom of the enolate nucleophile, while the nitroalkene coordinates via hydrogen bonding to the ammonium function of the quinuclidine unit of the catalyst. Hence, the canted directionality of the squaramide (NH)(2) motif, favoring one-atom binding, might be decisive for the selectivity of the reaction. The absolute configuration of the major (-)-(R) enantiomer of the product is assigned computationally according to its optical rotation

Asymmetric Michael Additions of 4‑Hydroxycoumarin to β‑Nitrostyrenes with Chiral, Bifunctional Hydrogen-Bonding Catalysts

Enantioselective Michael additions of 4-hydroxycoumarin to β-nitrostyrenes are catalyzed by different chiral, bifunctional hydrogen-bonding catalysts, based on thiourea- and squaramide motifs. The scope of the catalysis is tested by employing a series of substituted β-nitrostyrenes as well as different solvents. The 3,5-bis­(trifluoromethyl)­phenyl- and quinine-substituted squaramide catalyst is shown to be the most selective catalyst, resulting in 78% yield and 81% ee. Computational analyses of transition structures with different binding modes show that the most favored transition structure exhibits squaramide (NH)₂ binding to an oxygen atom of the enolate nucleophile, while the nitroalkene coordinates via hydrogen bonding to the ammonium function of the quinuclidine unit of the catalyst. Hence, the canted directionality of the squaramide (NH)₂ motif, favoring one-atom binding, might be decisive for the selectivity of the reaction. The absolute configuration of the major (−)-(<i>R</i>) enantiomer of the product is assigned computationally according to its optical rotation

Anion Recognition with Hydrogen-Bonding Cyclodiphosphazanes

Modular cyclodiphosph(V)azanes are synthesised and their affinity for chloride and actetate anions were compared to those of a bisaryl urea derivative (1). The diamidocyclodiphosph(V)azanes cis-[{ArNHP(O)(mu-tBu)}(2)] [Ar=Ph (2) and Ar=m-(CF3)(2)Ph (3)] were synthesised by reaction of [{ClP(mu-NtBu)}(2)] (4) with the respective anilines and subsequent oxidation with H2O2. Phosphazanes 2 and 3 were obtained as the cis isomers and were characterised by multinuclear NMR spectroscopy, FTIR spectroscopy, HRMS and single-crystal X-ray diffraction. The cyclodiphosphazanes 2 and 3 readily co-crystallise with donor solvents such as MeOH, EtOH and DMSO through bidentate hydrogen bonding, as shown in the X-ray analyses. Cyclodiphosphazane 3 showed a remarkably high affinity (log[K]=5.42) for chloride compared with the bisaryl urea derivative 1 (log[K]=4.25). The affinities for acetate (AcO-) are in the same range (3: log[K]=6.72, 1: log[K]=6.91). Cyclodiphosphazane 2, which does not contain CF3 groups, exhibits weaker binding to chloride (log[K]=3.95) and acetate (log[K]=4.49). DFT computations and X-ray analyses indicate that a squaramide-like hydrogen-bond directionality and C-alpha-H interactions account for the efficiency of 3 as an anion receptor. The C-alpha-H groups stabilise the Z,Z-3 conformation, which is necessary for bidentate hydrogen bonding, as well as coordinating with the anion

Balancing Flexibility and Rigidity: Do Unions Make Sense in the On-Demand Economy

[Summary] Unionization – the organization of workers to act collectively to obtain higher wages or better working conditions – has a storied history. While precursors to trade unions such as guilds existed before the Revolutionary War, the modern union did not come into its own until after the Industrial Revolution. As we move into a new economic era, the necessity and use of unions is once again called into question