Staphylococcus aureus is able to generate resistance to novel lipoglycopeptide antibiotic gausemycin A

Antibacterial activity of Bajakah Kalalawit phenolic against Staphylococcus aureus and possible use of phenolic nanoparticles

Dayak tribes indigenous to the Indonesian island of Borneo has been using Bajakah Kalalawit (Uncaria gambir Roxb.) as traditional medicine for ages. This inspired us to develop phenolic from Bajakah Kalalawit extract as antibacterial agent. The extraction was done through decoction method and the determination of phenolic concentration was done using a visible spectrophotometer and Folin-Ciocalteu reagent (mixture of phosphotungstic and phosphomolybdic acids). We investigated the possibility of developing phenolic nanoparticle for future work. Kirby-Bauer method was used to assess antibacterial activity of phenolic against Staphylococcus aureus and the results were compared to Chloramphenicol in terms of its efficacy and duration of inhibition. This study contributes to the ongoing effort to address antibiotic resistance through the development of innovative antibacterial agents derived from natural sources. The results provide valuable insights into the potential of Bajakah Kalalawit phenolic extracts as a promising avenue for combating bacterial infections in the future.

Unearthing naturally-occurring cyclic antibacterial peptides and their structural optimization strategies

Natural products with antibacterial activity are highly desired globally to combat against multidrug-resistant (MDR) bacteria. Antibacterial peptide (ABP), especially cyclic ABP (CABP), is one of the abundant classes. Most of them were isolated from microbes, demonstrating excellent bactericidal effects. With the improved proteolytic stability, CABPs are normally considered to have better druggability than linear peptides. However, most clinically-used CABP-based antibiotics, such as colistin, also face the challenges of drug resistance soon after they reached the market, urgently requiring the development of next-generation succedaneums. We present here a detail review on the novel naturally-occurring CABPs discovered in the past decade and some of them are under clinical trials, exhibiting anticipated application potential. According to their chemical structures, they were broadly classified into five groups, including (i) lactam/lactone-based CABPs, (ii) cyclic lipopeptides, (iii) glycopeptides, (iv) cyclic sulfur-rich peptides and (v) multiple-modified CABPs. Their chemical structures, antibacterial spectrums and proposed mechanisms are discussed. Moreover, engineered analogs of these novel CABPs are also summarized to preliminarily analyze their structure-activity relationship. This review aims to provide a global perspective on research and development of novel CABPs to highlight the effectiveness of derivatives design in identifying promising antibacterial agents. Further research efforts in this area are believed to play important roles in fighting against the multidrug-resistance crisis.

Lipid-Centric Approaches in Combating Infectious Diseases: Antibacterials, Antifungals and Antivirals with Lipid-Associated Mechanisms of Action

One of the global challenges of the 21st century is the increase in mortality from infectious diseases against the backdrop of the spread of antibiotic-resistant pathogenic microorganisms. In this regard, it is worth targeting antibacterials towards the membranes of pathogens that are quite conservative and not amenable to elimination. This review is an attempt to critically analyze the possibilities of targeting antimicrobial agents towards enzymes involved in pathogen lipid biosynthesis or towards bacterial, fungal, and viral lipid membranes, to increase the permeability via pore formation and to modulate the membranes' properties in a manner that makes them incompatible with the pathogen's life cycle. This review discusses the advantages and disadvantages of each approach in the search for highly effective but nontoxic antimicrobial agents. Examples of compounds with a proven molecular mechanism of action are presented, and the types of the most promising pharmacophores for further research and the improvement of the characteristics of antibiotics are discussed. The strategies that pathogens use for survival in terms of modulating the lipid composition and physical properties of the membrane, achieving a balance between resistance to antibiotics and the ability to facilitate all necessary transport and signaling processes, are also considered.

Gausemycin A-Resistant Staphylococcus aureus Demonstrates Affected Cell Membrane and Cell Wall Homeostasis

Antibiotic resistance is a significant and pressing issue in the medical field, as numerous strains of infectious bacteria have become resistant to commonly prescribed antibiotics. Staphylococcus aureus is a bacterium that poses a grave threat, as it is responsible for a large number of nosocomial infections and has high mortality rates worldwide. Gausemycin A is a new lipoglycopeptide antibiotic that has considerable efficacy against multidrug-resistant S. aureus strains. Although the cellular targets of gausemycin A have been previously identified, detailing the molecular processes of action is still needed. We performed gene expression analysis to identify molecular mechanisms that may be involved in bacterial resistance to gausemycin A. In the present study, we observed that gausemycin A-resistant S. aureus in the late-exponential phase showed an increased expression of genes involved in cell wall turnover (sceD), membrane charge (dltA), phospholipid metabolism (pgsA), the two-component stress-response system (vraS), and the Clp proteolytic system (clpX). The increased expression of these genes implies that changes in the cell wall and cell membrane are essential for the bacterial resistance to gausemycin A. In the stationary phase, we observed a decrease in the expression of genes involved in the phospholipid metabolism (mprF) and Clp proteolytic system (clpX).