Innovations in pediatric drug formulations and administration technologies for low resource settings

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Despite advances in regulations and initiatives to increase pediatric medicine development, there is still an unmet need for age-appropriate medicines for children. The availability of pediatric formulations is particularly lacking in resource poor areas, due to, for example, area-specific disease burden and financial constraints, as well as disconnected supply chains and fragmented healthcare systems. The paucity of authorized pediatric medicines often results in the manipulation and administration of products intended for adults, with an increased risk of mis-dosing and adverse reactions. This article provides an overview of the some of the key difficulties associated with the development of pediatric medicines in both high and low resource areas, and highlights shared and location specific challenges and opportunities. The utilization of dispersible oral dosage forms and suppositories for low and middle-income countries (LMICs) are described in addition to other platform technologies that may in the future offer opportunities for future pediatric medicine development for low resource settings

Risk assessment and absconding: Perceptions, understandings and responses of mental health nurses

Aims and objectives: This paper reports mental health nurses' perspectives of absconding. The aims of the study were to explore nurses' perceptions of risk assessment and management practices regarding absconding from acute inpatient psychiatric settings, and their affective responses when patients absconded. Background: Nurses are directly involved in managing the risk of patients leaving hospital while acutely unwell, as well as dealing with the implications of an absconding event. However, despite their key role, few studies have explored nurses' perceptions of absconding. Design: An interpretive inquiry was undertaken using a systematic thematic approach. Methods: Mental health nurses (n = 11) from three acute inpatient mental health units in Australia took part in semi-structured interviews, with a focus on the nurses' experiences of working with patients who had absconded. Data were analysed using systematic thematic coding procedures. Results: Nurses' assessment of a patient's risk of absconding involved the use of clinical judgement, focusing on markers of absconding including the patient's history and clinical presentation. The acuity of the perceived risk determined the type of risk management strategy implemented, which could include support, observation and/or the use of containment procedures. Nurses responded with a myriad of affective reactions when patients absconded depending on their assessment of the patient's risk. Conclusions: Support and debriefing is required for mental health nurses following an absconding event. Additional research is vital to identify alternative absconding assessment and management strategies to ensure the best possible outcome for patients and nurses. Relevance to clinical practice: Mental health nurses play a central role in risk assessment and management for absconding, with fear of repercussions a significant consequence for them. This research highlights the importance of both clinical judgment and standardised instruments in assessing absconding risk. Further research is needed to identify alternative evidence-based absconding management strategies to support nursing practice

Generation of thiocillin variants by prepeptide gene replacement and in vivo processing by Bacillus cereus

(Figure Presented) The thiocillins are natural-product antibiotics derived from ribosomally encoded peptides that undergo extensive posttranslational modifications to yield the mature trithiazolylpyridine-containing macrocyclic compound. Poor pharmacokinetic properties have prevented the clinical use of these highly potent antibiotics. Through in vivo manipulation of the gene responsible for production of the thiocillin precursor peptide, we have generated 65 novel thiocillin variants, allowing us to explore structure-activity relationships involved in both precursor peptide maturation and antibiotic activity

Thiazolyl peptide antibiotic biosynthesis: A cascade of post-translational modifications on ribosomal nascent proteins

Antibiotics of the thiocillin, GE2270A, and thiostrepton class, which block steps in bacterial protein synthesis, contain a trithiazolyl (tetrahydro)pyridine core that provides the architectural constraints for high affinity binding to either the 50 S ribosomal subunit or elongation factor Tu. These mature antibiotic scaffolds arise from a cascade of post-translational modifications on 50-60-residue prepeptide precursors that trim away the N-terminal leader sequences (∼40 residues) while the C-terminal 14-18 residues are converted into the mature scaffold. In the producing microbes, the genes encoding the prepeptide open reading frames are flanked in biosynthetic clusters by genes encoding post-translational modification enzymes that carry out lantibiotic-type dehydrations of Ser and Thr residues to dehydroamino acid side chains, cyclodehydration and oxidation of cysteines to thiazoles, and condensation of two dehydroalanine residues en route to the (tetrahydro)pyridine core. The trithiazolyl pyridine framework thus arises from post-translational modification of the peptide backbone of three Cys and two Ser residues of the prepeptide

Genetic interception and structural characterization of thiopeptide cyclization precursors from bacillus cereus

The pyridine core of the thiocillins has long been postulated to arise from a late-stage tail-to-tail condensation of two dehydroalanines. Genetic disruption of tclM, a proposed "Diels-Alderase", allowed isolation of acyclic precursors to this pyridine ring. The isolated products possess the full cohort of post-translational modifications that are normally displayed by the thiocillins, including dehydrobutyrines, thiazoles, C-terminal decarboxylation, and the two previously unconfirmed dehydroalanines. Additionally, leader peptides have undergone extensive N-terminal degradation and the remaining leader peptide residues have been N-succinylated. These results identify TclM and its homologues in other thiazolyl peptide producing strains as the enzymes responsible for the trans-annular heteroannulation at core of this class of molecules

Manipulation of thiocillin variants by prepeptide gene replacement: Structure, conformation, and activity of heterocycle substitution mutants

Bacillus cereus ATCC 14579 converts the C-terminal 14 residues of a 52-mer prepeptide into a related set of eight variants of the thiocillin subclass of thiazolyl peptide antibiotics by a cascade of post-translational modifications that alter 13 of those 14 residues. We have introduced prepeptide gene variants into a knockout strain to conduct an alanine scan of all 14 progenitor residues, as well as a serine scan of the six cysteine residues that are converted to thiazoles in the mature natural product. No mature scaffolds were detected for the S1A and S10A mutants, consistent with their roles as the source of the pyridine core. In both the alanine and serine scans, only one substitution mutant failed to produce a mature scaffold: cysteine 11. Cysteine to serine mutants gave mixture of dehydrations, aromatizations, and unaltered alcohol side chains depending on position. Overall, substitutions that altered the trithiazolylpyridine core or reduced the conformational rigidity of the 26-membered macrocyclic loop led to loss of antibiotic activity. In total, 21 peptide mutants were cultured, from which production of 107 compounds was observed and 94 compounds, representing 17 structural mutants, were assayed for antibiotic activity. High-resolution NMR solution structures were determined for one mutant and one wild-type compound. These structures demonstrate that the tight conformational rigidity of the natural product is severely disrupted by loss of even a single heterocycle, perhaps accounting for the attendant loss of activity in such mutants

Generation of thiocillin ring size variants by prepeptide gene replacement and in vivo processing by Bacillus cereus

The thiocillins from Bacillus cereus ATCC 14579 are natural products from the broader class of thiazolyl peptides. Their biosynthesis proceeds via extensive post-translational modification of a ribosomally encoded precursor peptide. This post-translational tailoring involves a key step formal cycloaddition between two distal serine residues. In the wild-type structure, this cycloaddition forms a major macrocycle circumscribed by 26-atoms (shortest path). Results presented herein demonstrate the promiscuity of this last step by means of a set of "competition" experiments. Cyclization proceeds in many cases to provide altered ring sizes, giving access to several variant rings sizes that have not previously been observed in nature

A Backup Plan for Self-Protection: S-Methylation of Holomycin Biosynthetic Intermediates in Streptomyces clavuligerus

Biosynthesis of the dithiolopyrrolone antibiotic holomycin in Streptomyces clavuligerus involves the closure of a pair of enethiols to a cyclic disulfide. We have shown that the dithiol oxidase HlmI is responsible for the disulfide formation and this enzyme also plays a role in self-protection. In the present study, we examine how S. clavuligerus deals with the proposed toxic dithiol intermediates when hlmI is deleted. We used differential NMR spectroscopy and mass spectrometry to profile the metabolomes of hlmI deletion mutants along with the wild-type strain and a holomycin-overproducing strain. A number of metabolites unique to ΔhlmI strains were identified. In these metabolites the enethiols have been incapacitated by a combination of mono- and di-S-methylation. We also observed an intriguing dimeric thioether adduct in low quantities in the wild-type strain and at much higher levels in the ΔhlmI strains. The structures of these novel metabolites highlight the reactivity of the dihydrodithiolopyrrolone scaffold. Furthermore, bioassays suggest that modification of the enethiol warhead by S-alkylation provides a host strategy for detoxification, one that is shared amongst multiple species producing such bioactive disulfide natural products

Dithiolopyrrolones: biosynthesis, synthesis, and activity of a unique class of disulfide-containing antibiotics

Dithiolopyrrolone natural products have unique structures and exhibit a broad-spectrum of antimicrobial and anticancer activities. Isolated in the late 1940s, these molecules have attracted an increasing interest towards their biosynthesis, synthesis and mechanisms of action

Generating a positive energy balance from using rice straw for anaerobic digestion

About 150 million metric tons of rice straw is produced in Southeast Asian countries every year. Several barriers impeding the collection of rice straw from the fields as well as the lack of knowledge on alternative uses of rice straw led to the practice of burning which causes air pollution and greenhouse gas emissions. To identify the benefits and uses of rice straw for energy generation is the main objective of this research. The study evaluated the energy balance of the rice straw supply chain and energy conversion through anaerobic digestion (AD). The input energy was categorized either as direct and indirect energy. Direct energy included agricultural inputs, fuel consumption and manpower. Fuel consumption was measured directly from the vehicles and equipment used in the experiment while manpower was measured using the metabolic equivalent of task (MET) based on labor time per ton of straw. Indirect energy was calculated based on the energy for the manufacture, lubrication, and maintenance of machines and equipment. The net energy of the rice straw supply chain for biogas generation through AD is 3,500 MJ per ton of straw. This rice straw management option can provide a 70% net output energy benefit. The research highlighted the potential of rice straw as a clean fuel source with a positive energy balance, helping to reduce greenhouse gas emissions compared with the existing practice of burning it in the field