Health and care workers in long-term care facilities and their role in preventing emerging infectious diseases: A scoping review.

BACKGROUND: The COVID-19 pandemic has had a tremendous impact on healthcare systems worldwide. In particular, long-term care facilities have proved more susceptible to infection as they care for vulnerable populations at high risk of chronic illness. How this impacts the role and core competencies of health and care workers in these facilities remains less understood. AIM: Describe how health and care workers contribute to the prevention of emerging infectious diseases in long-term care facilities. DESIGN: A scoping review. METHODS: A systematic search of literature dating from 2002 to 2022 was conducted in the following databases: EMBASE, Medline (Ovid), Cochrane Library, CINAHL Plus with Full Text (EBSCOhost), Web of Science, and AgeLine. Studies were selected if they focused on health and care workers in long-term care facilities, offered a perspective on the prevention of emerging infectious diseases or infection prevention and control, and were original qualitative or quantitative studies in English. Data were extracted, cross-checked and analyzed by two researchers, and any difference in views regarding the appropriateness of literature would be resolved by consulting a third researcher. An inductive descriptive approach was applied for the analysis of results, and themes were established via consensus meetings. RESULTS: A total of fourteen studies from Asia, Europe, and the Americas were included. Three themes emerged from the review: "The roles of health and care workers evolve with the times", "The core competencies of health and care workers are essential for preventing emerging infectious diseases in long-term care facilities" and "The key to successful prevention of emerging infectious diseases in long-term care facilities is through a systematic, comprehensive effort that mobilize health and care workers at all levels". Health and care workers had to take on increasingly complex roles and rely on their core competencies to cope with epidemic changes, and facility resources, employee quality and management models were found to have significantly improved infection prevention and control outcomes. CONCLUSIONS: The roles of health and care workers are evolving, and effective infection prevention within long-term care facilities depends on their ability to perform core competencies with skill and confidence. Moreover, a systematic, comprehensive framework, for which this paper proposes three guidelines, is urgently needed to ensure consistent policy implementation within the facility as well as support and access to resources for health and care workers. CLINICAL RELEVANCE: Infection prevention efforts within long-term care facilities must take into account the evolving roles of health and care workers, with a focus on guaranteeing access to resources, training and support that will help them gain the core competencies necessary for juggling those roles. In addition, there is an urgent need for research instruments that will help assess those competencies and identify areas of improvement.

Structural Basis of Low-Molecular-Weight Thiol Glycosylation in Lincomycin A Biosynthesis.

The involvement of low-molecular-weight thiols in the biosynthesis of natural products is rarely reported. During lincomycin A biosynthesis, ergothioneine (EGT) is incorporated in the S-glycosylation catalyzed by LmbT. In contrast to the widely reported glycosylation of nitrogen and oxygen atoms, the glycosylation of sulfur atoms is less studied. In particular, the crystal structure of enzymes that glycosylate thiols on small molecules rather than peptides has not been reported. Here, we report the crystal structures of LmbT in apo form and in complex with GDP and EGT S-conjugated lincosamine. We found that LmbT has a characteristic glycosyltransferase type B fold, which forms a symmetric homotetramer. The substrates are bound deeply in the catalytic cleft. Consistent with the substrate structure, LmbT does not have the large peptide binding groove of the previously reported S-glycosyltransferase. Combined with site-directed mutagenesis, we propose a catalytic mechanism for the unusual EGT-mediated S-glycosylation in natural product biosynthesis.

Oxidase Heterotetramer Completes 1-Azabicyclo[3.1.0]hexane Formation with the Association of a Nonribosomal Peptide Synthetase.

Ficellomycin, azinomycins, and vazabitide A are nonribosomal peptide natural products characterized by an amino acid unit that contains a similar 1-azabicyclo[3.1.0]hexane (ABCH) pharmacophore. This unit is derived from diamino-dihydroxy-heptanic acid (DADH); however, the process through which linear DADH is cyclized to furnish an ABCH ring system remains poorly understood. Based on the reconstitution of the route of the ABCH-containing unit by blending genes/enzymes involved in the biosynthesis of ficellomycin and azinomycins, we report that ABCH formation is completed by an oxidase heterotetramer with the association of a nonribosomal peptide synthetase (NRPS). The DADH precursor was prepared in Escherichia coli to produce a conjugate subjected to in vitro enzymatic hydrolysis for offloading from an amino-group carrier protein. To furnish an aziridine ring, DADH was processed by C7-hydroxyl sulfonation and sulfate elimination-coupled cyclization. Further cyclization leading to an azabicyclic hexane pharmacophore was proved to occur in the NRPS, where the oxidase heterotetramer functions in trans and catalyzes α,ß-dehydrogenation to initiate the formation of a fused five-membered nitrogen heterocycle. The identity of ABCH was validated by utilization of the resultant ABCH-containing unit in the total biosynthesis of ficellomycin. Biochemical characterization, crystal structure, and site-specific mutagenesis rationalize the catalytic mechanism of the unusual oxidase heterotetramer.

Tyrosine-targeted covalent inhibition of a tRNA synthetase aided by zinc ion.

Aminoacyl-tRNA synthetases (AARSs), a family of essential protein synthesis enzymes, are attractive targets for drug development. Although several different types of AARS inhibitors have been identified, AARS covalent inhibitors have not been reported. Here we present five unusual crystal structures showing that threonyl-tRNA synthetase (ThrRS) is covalently inhibited by a natural product, obafluorin (OB). The residue forming a covalent bond with OB is a tyrosine in ThrRS active center, which is not commonly modified by covalent inhibitors. The two hydroxyl groups on the o-diphenol moiety of OB form two coordination bonds with the conserved zinc ion in the active center of ThrRS. Therefore, the ß-lactone structure of OB can undergo ester exchange reaction with the phenolic group of the adjacent tyrosine to form a covalent bond between the compound and the enzyme, and allow its nitrobenzene structure to occupy the binding site of tRNA. In addition, when this tyrosine was replaced by a lysine or even a weakly nucleophilic arginine, similar bonds could also be formed. Our report of the mechanism of a class of AARS covalent inhibitor targeting multiple amino acid residues could facilitate approaches to drug discovery for cancer and infectious diseases.

Tracing of Acyl Carrier Protein-channeled Mitomycin Intermediates in Streptomyces caespitosus Facilitates Characterization of the Biosynthetic Steps for AHBA-GlcN Formation and Processing.

Mitomycins are a family of naturally occurring, potent alkylating agents in which the C member has been clinically used for cancer chemotherapy for over 5 decades. In Streptomyces caespitosus, mitomycins are derived from an N-glycoside composed of a 3-amino-5-hydroxybenzoic acid (AHBA) unit and a d-glucosamine (GlcN) unit; however, how this N-glycoside is formed and rearranged to a mitosane, for example, the compact polycyclic ring system of mitomycin C, remains elusive. Benefiting from the development of a method used to trace the mitomycin intermediates that accumulate on an acyl carrier protein (ACP), we here dissect the enzymatic steps for AHBA-GlcN formation and processing to underlie the mitosane structure. Following the N-glycosylation of AHBA with activated N-acetyl-GlcN, deacetylation occurs on ACP to provide AHBA-GlcN. Then, the sugar portion of this N-glycoside is transformed into a linear aminodiol that terminates with an epoxyethane, yielding an ACP-channeled intermediate that is ready for mitosane formation through crosslinking between the AHBA and linearized sugar units. This transformation is unusual and relies on the functional association of a dihydronicotinamide adenine dinucleotide (phosphate)-dependent protein with a radical S-adenosyl-l-methionine protein. Characterization of these ACP-based enzymatic steps for AHBA-GlcN formation and processing sheds light on the poorly understood biosynthetic pathway of mitomycins.

Study on the potential application of salivary inorganic anions in clinical diagnosis by capillary electrophoresis coupled with contactless conductivity detection.

A capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of inorganic metabolites (thiocyanate, nitrite and nitrate) in human saliva. Field amplified sample injection, as a simple sample stacking technique, was used in conjunction for online preconcentration of above inorganic anions. A selective separation for the target anions from other coexisting constituents present in saliva could be obtained within 14min in a 10mmol/L His-90mmol/L HAc buffer (pH 3.70) at the separation voltage of -18kV. The limits of detection and limits of quantification of the three analytes were within the range of 3.1-4.9ng/mL (S/N=3) and 10-16ng/mL (S/N=10), respectively. The average recovery data were in the range of 81-108% at three different concentrations. This method provides a simple, rapid and direct approach for metabolite analyses of nitric oxide and cyanide based on noninvasive saliva sample, which presents a potential fast screening tool for clinical test.

A new particle swarm optimization-based method for phase unwrapping of MRI data.

A new method based on discrete particle swarm optimization (dPSO) algorithm is proposed to solve the branch-cut phase unwrapping problem of MRI data. In this method, the optimal order of matching the positive residues with the negative residues is first identified by the dPSO algorithm, then the branch cuts are placed to join each pair of the opposite polarity residues, and in the last step phases are unwrapped by flood-fill algorithm. The performance of the proposed algorithm was tested on both simulated phase image and MRI wrapped phase data sets. The results demonstrated that, compared with conventionally used branch-cut phase unwrapping algorithms, the dPSO algorithm is rather robust and effective.