Microwave-assisted synthesis and antimicrobial screening of new imidazole derivatives bearing 4-thiazolidinone nucleus

A new series of compounds 2-((1-(4-(4-arylidene-2-methyl-5-oxo-4,5-dihydro-1H-imidazol-1-yl)phenyl)ethylidene)hydrazono)thiazolidin-4-ones (4a–o) have been synthesized under conventional and microwave irradiation method. All compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus by bioassays, namely serial broth dilution. The synthesized compounds showed potent antimicrobial activity against tested microorganisms. Compounds 4h, 4j, 4m and 4n were the most potent amongst tested compounds.     

Demonstration of the role of cell wall homeostasis in Staphylococcus aureus growth and the action of bactericidal antibiotics

Bacterial cell wall peptidoglycan is essential, maintaining both cellular integrity and morphology, in the face of internal turgor pressure. Peptidoglycan synthesis is important, as it is targeted by cell wall antibiotics, including methicillin and vancomycin. Here, we have used the major human pathogen Staphylococcus aureus to elucidate both the cell wall dynamic processes essential for growth (life) and the bactericidal effects of cell wall antibiotics (death) based on the principle of coordinated peptidoglycan synthesis and hydrolysis. The death of S. aureus due to depletion of the essential, two-component and positive regulatory system for peptidoglycan hydrolase activity (WalKR) is prevented by addition of otherwise bactericidal cell wall antibiotics, resulting in stasis. In contrast, cell wall antibiotics kill via the activity of peptidoglycan hydrolases in the absence of concomitant synthesis. Both methicillin and vancomycin treatment lead to the appearance of perforating holes throughout the cell wall due to peptidoglycan hydrolases. Methicillin alone also results in plasmolysis and misshapen septa with the involvement of the major peptidoglycan hydrolase Atl, a process that is inhibited by vancomycin. The bactericidal effect of vancomycin involves the peptidoglycan hydrolase SagB. In the presence of cell wall antibiotics, the inhibition of peptidoglycan hydrolase activity using the inhibitor complestatin results in reduced killing, while, conversely, the deregulation of hydrolase activity via loss of wall teichoic acids increases the death rate. For S. aureus, the independent regulation of cell wall synthesis and hydrolysis can lead to cell growth, death, or stasis, with implications for the development of new control regimes for this important pathogen.

How bacteria grow and divide is a fundamental question in microbiology, where many of the essential processes involved are the targets of clinically important antibiotics. The cell wall is crucial for bacterial survival, forming the interface between the external and internal environments and maintaining internal turgor pressure (1, 2). The major cell wall structural component is peptidoglycan (PG), a polymer of glycan strands and peptide cross-links (3–5), the synthesis of which is the target of antibiotics including β-lactams and glycopeptides (6). These cell wall antibiotics inhibit the final stages of PG synthesis where building blocks are incorporated into the existing structure via the action of penicillin-binding proteins (PBPs) (6). Several mechanisms linking the action of antibiotics to the inhibition of essential processes in cell wall growth and division have been suggested, including lytic and nonlytic death, oxidative stress, and futile PG synthesis (7–12).As a single macromolecule that surrounds the cell, PG can increase in surface area to permit growth and division while maintaining cellular integrity. It has been proposed that areal PG growth occurs as a consequence of both synthesis and hydrolysis (4, 13, 14), with new material being covalently bound to the existing macrostructure and hydrolysis of existing bonds allowing expansion. This leads to a simple set of hypotheses for growth but also makes predictions as to the effects of inhibition of PG homeostasis activities, including cell wall antibiotics (Fig. 1A). The lack of either PG synthesis or hydrolysis will result in cell death because of the continued activity of the other, but the loss of both will lead to stasis.Open in a separate windowFig. 1.The role of regulation of PG hydrolases (PGHs) by WalKR in life and death. (A) Predictive model for how cell wall homeostasis governs bacterial life and death. Both cell wall synthesis and hydrolysis are required for growth, loss of either results in death, or both, cell stasis. (B–H) Effect of 10 × minimum inhibitory concentration (MIC) vancomycin for 3 h on conditional lethal strain S. aureus P_spac-walKR (without inducer; WalKR OFF) compared to the control (with inducer; WalKR ON). (B) CFU relative to T = 0; after t test with Welch''s correction: P (WalKR OFF − WalKR OFF + vancomycin, **) = 6.9 × 10⁻³. (C and D) PG synthesis and transpeptidase activity measured by ¹⁴C-GlcNAc and Atto 488 dipeptide (53) incorporation, normalized against WalKR ON. (E) Transmission electron microscopy (TEM) (scale bars, 300 nm). (F) Quantification of bacterial phenotypes (SI Appendix, Fig. S2; dark green: no septum, mid-green: incomplete septum, light green: complete septum, and yellow: growth defects). For samples shown, the number of individual cells quantified was n > 300. (G) AFM topographic images of sacculi (scale bars, 150, 300, and 300 nm; data scales [DS], 85, 200, and 85 nm, respectively, from Left to Right). (i) Insets show sacculus external architecture from Left to Right, (WalKR ON) from dashed box in panel G, (WalKR OFF) from SI Appendix, Fig. S2E, (WalKR OFF+Van) from SI Appendix, Fig. S2D, respectively (scale bars, 50 nm; DS, 30, 52, and 32 nm, respectively, from Left to Right; images were analyzed with NanoscopeAnalysis from Bruker using the default color scale). (H) Thickness distribution values for sacculi with SD (n = 5). For sample size and data reproducibility, see Materials and Methods.Staphylococcus aureus is a major human antimicrobial-resistant pathogen. As a spheroid cell with a simple growth and division cycle, it forms an excellent subject to demonstrate the basic principles underlying growth, division, and the action of antibiotics. Many organisms have multiple PBPs, but S. aureus has only four, of which PBP1 and PBP2 are essential for growth and division (15–19). S. aureus also has many PG hydrolases (PGHs), including SagB, which is involved in cell growth (20, 21). The bifunctional Atl is involved in generalized cell lysis and cell separation after septation and contains both amidase and glucosaminidase domains (22, 23). PGHs often show functional redundancy with several enzymes involved in the same process (20, 24). In S. aureus, no individual PGH alone has been shown to be required for either growth or division, but multiple PGHs are positively regulated by an essential two-component system, WalKR (25–27), further suggesting that their collective activity is required.Recently, using atomic force microscopy (AFM), we have revealed that the molecular architecture of the PG is that of an expanded hydrogel whose mature external surface is a porous open network but with an interior surface characterized by a much smoother and denser mesh of PG material (28). This provides an architectural framework from which to begin to elucidate the roles of PG synthesis and hydrolysis. Here, we have taken an integrated approach to determine the role of PG homeostasis in S. aureus growth, division, and the bactericidal action of cell wall antibiotics.     

Advances in oral transmucosal drug delivery

The successful delivery of drugs across the oral mucosa represents a continuing challenge, as well as a great opportunity. Oral transmucosal delivery, especially buccal and sublingual delivery, has progressed far beyond the use of traditional dosage forms with novel approaches emerging continuously. This review highlights the physiological challenges as well as the advances and opportunities for buccal/sublingual drug delivery. Particular attention is given to new approaches which can extend dosage form retention time or can be engineered to deliver complex molecules such as proteins and peptides. The review will also discuss the physiology and local environment of the oral cavity in vivo and how this relates to the performance of transmucosal delivery systems.     

Synthesis and antimicrobial screening of novel series of imidazo-[1,2-a]pyridine derivatives

In an attempt to find new bio-active molecules, a series of mannich bases N,N-dimethyl-1-(7-methyl-2-(aryl)imidazo[1,2-a]pyridin-3-yl)methanamines 4a–l were synthesized by mannich reaction of 7-methyl-2-(aryl)imidazo-[1,2-a]pyridines 3a–l with paraformaldehyde and N,N-dimethyl amine. Compounds 3a–l were prepared from reaction between different substituted 2-bromo-1-(aryl)ethanones 2a–l and 4-methylpyridin-2-amine 1. Structures of these compounds were confirmed by IR, ¹H NMR, ¹³C NMR, and mass spectral data. Antimicrobial screening of title compounds 3a–l was examined against Gram-positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Some derivatives bearing halogen group was found to be equipotent or more potent than commercial drugs, against most of the employed strains, as evident from the screening data.     

Management of pediatric single-level vertebral hemangiomas presenting with myelopathy by three-pronged approach (ethanol embolization,laminectomy, and instrumentation): a single-institute experience

Purpose

Pediatric vertebral hemangiomas (VH) are exceedingly rare benign and highly vascular tumours of the spine. There are no guidelines available for management of these patients in literature. Purpose of this study is to evaluate the role of intraoperative ethanol embolization, surgical decompression, and instrumented fusion in pediatric symptomatic VH with single-level involvement.

Methods

Surgery consisted of intraoperative bilateral pedicular absolute alcohol injection and laminectomy at the level of pathology followed by a short-/long-segment instrumented fusion using pedicle screws and rod. Seven patients (mean age 14 ± 2.4 years, range 10–17 years, five females and two males) (age < 18 years) who were treated using this technique at our institute since March 2008 to December 2013 were enrolled in this retrospective study. Demographical, clinical, radiological, operative details, and postoperative events were retrieved from hospital records. During follow-up visits, clinical status and imaging were recorded. Outcome assessed with clinical and neurological outcome score of American Spinal Injury Association (

Results

Duration of symptoms ranged from 3 to 60 months (mean, 14.7 ± 20.4 months). Clinical features include myelopathy with motor and sensory involvement in all (five were paraplegic), back pain in two patients, and bladder involvement in two patients. The preoperative American Spinal Injury Association (ASIA were E in six patients and D in one patient at the last follow-up.

Conclusion

The present study is the largest series of pediatric symptomatic VH. This procedure is a safe, efficient method to treat symptomatic pediatric VH with severe cord compression. It seems to serve the purpose of providing embolization, cord decompression, rigid fusion at the same sitting without adding new morbidity, and preventing excessive blood loss.

     

Itraconazole nanosuspension for oral delivery: Formulation, characterization and in vitro comparison with marketed formulation

Background and the purpose of the study

Itraconazole is a poorly water soluble drug which results in its insufficient bioavailability. The purpose of the present study was to formulate Itraconazole in a nanosuspension to increase the aqueous solubility and to improve its formulation related parameters, dissolution and hence oral bioavailability.

Methods

Itraconazole nanosuspension was prepared by pearl milling technique using zirconium oxide beads as a milling media, Poloxamer 407 as a stabilizer and glycerol as a wetting agent. Effects of various process parameters like, stirring time and the ratio of the beads were optimized by keeping drug:surfactant:milling media (1:3.0:50) as a constant initially and then optimized process parameters were used to optimize formulation parameters by 32 factorial designs. The optimized nanosuspension was lyophilized using mannitol (1:1 ratio) as a cryoprotectant. Nanosuspension was characterized by particle size and size distribution, drug content, scanning electron microscopy, differential scanning colorimetry and X-ray diffraction techniques.

Results

Optimized nanosuspension showed spherical shape with surface oriented surfactant molecules and a mean particle diameter of 294 nm. There was no significant change in crystalline nature after formulation and it was found to be chemically stable with high drug content.

Conclusion

The in vitro dissolution profile of the optimized formulation compared to the pure drug and marketed formulation (Canditral Capsule) by using 0.1N Hydrochloric acid as release medium showed higher drug release.