Mechanistic Insights of Drug Resistance in <em>Staphylococcus aureus</em> with Special Reference to Newer Antibiotics

Staphylococcus aureus is the most ubiquitous microorganism in both environment as well as animals and exists as commensal and pathogenic bacterium. In past few years it has been emerged as a superbug causing serious burden on healthcare system. This bacterium has been found to be the most resistant one toward most of the antibiotics due to its rapid structural and genetic modifications. This chapter will shed light on various types of molecular mechanisms responsible for resistance of Staphylococcus aureus showcasing how it has been emerged as a superbug. Moreover, the recent approaches which include exploring of different drug targets keeping in view the structural and functional behavior of the Staphylococcus aureus has also been discussed

Antimicrobial and antibiofilm effects of shikonin with tea tree oil nanoemulsion against <i>Candida albicans</i> and <i>Staphylococcus aureus</i>

The current work aims to develop a shikonin and tea tree oil loaded nanoemulsion system stabilized by a mixture of GRAS grade surfactants (Tween 20 and monoolein) and a cosurfactant (Transcutol P). This system was designed to address the poor aqueous solubility and photostability issues of shikonin. The authenticity of shikonin employed in this study was confirmed using nuclear magnetic resonance (NMR) spectroscopy. The optimized nanoemulsion exhibited highly favorable characteristics in terms of zeta potential (−23.8 mV), polydispersity index (0.216) and particle size (22.97 nm). These findings were corroborated by transmission electron microscopy (TEM) micrographs which confirmed the spherical and uniform nature of the nanoemulsion globules. Moreover, attenuated total reflectance (ATR) and X-ray diffraction analysis (XRD) analysis affirmed improved chemical stability and amorphization, respectively. Photodegradation studies were performed by exposing pure shikonin and the developed nanoemulsion to ultraviolet light for 1 h using a UV lamp, followed by high performance liquid chromatography (HPLC) analysis. The results confirmed that the developed nanoemulsion system imparts photoprotection to pure shikonin in the encapsulated system. Furthermore, the research investigated the effect of the nanoemulsion on biofilms formed by Candida albicans and methicillin resistant Staphylococcus aureus (MRSA). Scanning electron microscopy, florescence microscopy and phase contrast microscopy unveiled a remarkable reduction in biofilm area, accompanied by disruptions in the cell wall and abnormalities on the cell surface of the tested microorganisms. In conclusion, the nanoencapsulation of shikonin with tea tree oil as the lipid phase showcased significantly enhanced antimicrobial and antibiofilm potential compared to pure shikonin against resistant strains of Candida albicans and Staphylococcus aureus.</p

Targeting JAK/STAT signaling pathway and anti-inflammatory markers using bakuchiol isolated from Psoralea corylifolia for cytotoxicity of human squamous cell carcinoma (A431) cells

Objectives: Non melanoma skin cancers are common neoplasms worldwide. In India, squamous cell carcinoma (SCC), is the most prevalent skin disorder and its incidence rises quickly with cumulative exposure to sun. Numerous techniques are available for SCC but reversion and metastasis are common concern that needs effective and safe strategies for its control. With this in view, the study was planned to investigate the activity of Bakuchiol (Bak), traditionally used in various countries for curing skin ailments but its mechanism of action is unexplored. In our study, we explored anti-proliferative, pro-apoptotic and anti-inflammatory potential of Bak toward human squamous carcinoma (A431) cell line. Methods: The pure compound Bak was isolated from the plant Psoralea corylifolia and characterized using NMR, HRMS and FTIR. To explore their bioefficacy, different in vitro assays were performed against A431 cell line. To have molecular insights, RT-qPCR investigation was done to analyzed the expression level of inflammatory markers (TLR 9, IFN β, IL 23, JAK 3 and STAT 3). Results: The results showed the growth inhibitory effect on A431 cells after Bak treatment in dose-dependent way. To understand mode of cell death, cells were initially analyzed under phase-contrast, fluorescence and scanning electron microscope that showed characteristics of apoptosis. Furthermore, cell cycle studies with a flow cytometer were carried out which showed increased level of ROS, reduced MMP and cells arrested at G0/G1 phase in Bak treated cells further strengthening the induction of apoptosis. Moreover, RT-qPCR analysis indicated the downregulation of inflammatory markers in Bak-treated A431 cells that further confirmed its therapeutic role. The molecular docking study also confirmed that Bak has perfect scaffold that can complete the pharmacophoric need for JAK3 kinase inhibition. Conclusion: A critical analysis of results points towards the role of Bak in ameliorating inflammatory markers along with apoptosis induction in A431 cells by regulating the expression level of variable markers

Modulation of atrazine-induced chromosomal aberrations and cyclin-dependent kinases by aqueous extract of Roylea cinerea (D.Don) Baillon leaves in Allium cepa

Abstract Roylea cinerea (D.Don) Baillon an indigenous medicinal plant of Lamiaceae family used for the treatment of several diseases. In the present study, its aqueous (leaves) extract was tested for genoprotective action against atrazine-induced chromosomal aberrations in the root tip cells of Allium cepa. Atrazine is a herbicide of triazine class commonly used to inhibit the growth of broad leaf and grassy weeds. In order to find the concentration of atrazine that exhibits maximum toxicity, its different concentrations (1, 5 and 10 µg/mL) were tested. It was observed that 10 µg/mL concentration was more toxic as it reduced the mitotic index and also increased the chromosomal aberrations. Among all the tested concentrations of aqueous (leaves) extracts (0.25. 0.5, 1.0, 1.5 and 3.0 µg/mL), the3.0 µg/mL concentration in both modes of experiments i.e. pre and post showed a significant reduction in chromosomal aberrations induced by atrazine. To understand the mechanism of protection by plant extract on atrazine-induced chromosomal abnormalities the RT-qPCR studies were conducted to observe the expression of marker genes Cyclin-dependent kinases (CDKs) (CDKA:1, CDKB2:1 and CDKD1:1. For this, the RNA was extracted from root tips treated with extract along with atrazine by TRIzol®. It was observed that aqueous extract of Roylea cinerea (D.Don) Baillon leaves upregulated the CDKs gene expression in both the modes i.e. pre and post treatments. A critical analysis of results indicated that aqueous extract ameliorated the chromosomal aberrations caused by atrazine which may be be due to the increased expression level of CDKs genes