Lapatinib Acts against Biofilm Formation and the Hemolytic Activity of Staphylococcus aureus

Antibiofilm Activities of Multiple Halogenated Pyrimidines Against Staphylococcus aureus

Staphylococcus aureus, prevalent in hospital and community settings, forms biofilms that are highly resistant to antibiotics and immune responses, complicating treatment and contributing to chronic infections. These challenges underscore the need for novel treatments that target biofilm formation and effectively reduce bacterial virulence. This study investigates the antibiofilm and antimicrobial efficacy of novel halogenated pyrimidine derivatives against S. aureus, focusing on three compounds identified as potent biofilm inhibitors: 2,4-dichloro-5-fluoropyrimidine (24DC5FP), 5-bromo-2,4-dichloro-7H-pyrrolo[2,3-d]pyrimidine (24DC5BPP), and 2,4-dichloro-5-iodo-7H-pyrrolo[2,3-d]pyrimidine (24DC5IPP). The three active compounds are bacteriostatic. In particular, 24DC5FP at 5 µg/mL achieved a 95% reduction in hemolysis with a minimum inhibitory concentration (MIC) of 50 µg/mL. Interestingly, 24DC5FP increased cell size and produced wrinkled colonies. qRT-PCR analysis showed that 24DC5FP suppressed the gene expressions of agrA and RNAIII (quorum sensing regulator and effector), hla (α-hemolysin), nuc1 (nucleases nuc1), and saeR (S. aureus virulence regulator). These findings suggest that extensive halogenation enhances the antibiofilm and antivirulence activities of pyrimidine derivatives, offering a promising strategy for combatting S. aureus infections, including those resistant to conventional treatments.

Developing phytocompound-based new drugs against multi-drug-resistant Staphylococcus aureus

Staphylococcus aureus, a prevalent component of the human microbiota, is associated with skin infections to life-threatening diseases, presenting challenges in treatment options and necessitating the development of effective treatments. This study integrated computational and in vitro approaches to identify promising phytocompounds with therapeutic potential. Staphopain B emerged as a target protein for its role in immune evasion, exhibiting stability during molecular dynamic simulation (MDS) with a root mean square deviation value of 2.376 Å. Screening 115 phytocompounds with antibacterial properties from the PubChem database identified 12 with drug-like properties, nine of which showed superior binding affinity to Staphopain B compared to a commercial antibiotic, doxycycline (-7.8 kcal mol-1). Notably, epoxyazadiradione and nimbolide displayed higher estimated free energy of binding scores (-7.91 and -7.93 kcal mol-1, respectively), indicating strong protein-ligand interactions. The root mean square fluctuation values for epoxyazadiradione and nimbolide were 1.097 and 1.034 Å, respectively, which was confirmed through MDS. Crude ethanolic extracts (100% and 70%) of neem (Azadirachta indica) leaves demonstrated narrow inhibition against the bacteria in comparison to doxycycline in the disc-diffusion assay. This study underscores the potential of phytocompounds as therapeutic agents against S. aureus; however, further in vitro experiments and testing of the phytocompounds in vivo are required.

Identification of kinase modulators as host-directed therapeutics against intracellular methicillin-resistant Staphylococcus aureus

The increasing prevalence of antimicrobial-resistant Staphylococcus aureus strains, especially methicillin-resistant S. aureus (MRSA), poses a threat to successful antibiotic treatment. Unsuccessful attempts to develop a vaccine and rising resistance to last-resort antibiotics urge the need for alternative treatments. Host-directed therapy (HDT) targeting critical intracellular stages of S. aureus emerges as a promising alternative, potentially acting synergistically with antibiotics and reducing the risk of de novo drug resistance. We assessed 201 ATP-competitive kinase inhibitors from Published Kinase Inhibitor Sets (PKIS1 and PKIS2) against intracellular MRSA. Seventeen hit compounds were identified, of which the two most effective and well-tolerated hit compounds (i.e., GW633459A and GW296115X) were selected for further analysis. The compounds did not affect planktonic bacterial cultures, while they were active in a range of human cell lines of cervical, skin, lung, breast and monocyte origin, confirming their host-directed mechanisms. GW633459A, structurally related to lapatinib, exhibited an HDT effect on intracellular MRSA independently of its known human epidermal growth factor receptor (EGFR)/(HER) kinase family targets. GW296115X activated adenosine monophosphate-activated protein kinase (AMPK), thereby enhancing bacterial degradation via autophagy. Finally, GW296115X not only reduced MRSA growth in human cells but also improved the survival rates of MRSA-infected zebrafish embryos, highlighting its potential as HDT.

Comparative evaluation of small molecules reported to be inhibitors of Staphylococcus aureus biofilm formation

IMPORTANCE

Because biofilm formation is such a problematic feature of Staphylococcus aureus infections, much effort has been put into identifying biofilm inhibitors. However, the results observed with these compounds are often reported in isolation, and the methods used to assess biofilm formation vary between labs, making it impossible to assess relative efficacy and prioritize among these putative inhibitors for further study. The studies we report address this issue by directly comparing putative biofilm inhibitors using a consistent in vitro assay. This assay was previously shown to maximize biofilm formation, and the results observed with this assay have been proven to be relevant in vivo. Of the 19 compounds compared using this method, many had no impact on biofilm formation under these conditions. Indeed, only one proved effective at limiting biofilm formation without also inhibiting growth.

Repurposing of the antimalarial agent tafenoquine to combat MRSA

IMPORTANCE

This study represents the first investigation into the antimicrobial effect of TAF against S. aureus and its potential mechanisms. Our data highlighted the effects of TAF against MRSA planktonic cells, biofilms, and persister cells, which is conducive to broadening the application of TAF. Through mechanistic studies, we revealed that TAF targets bacterial cell membranes. In addition, the in vivo experiments in mice demonstrated the safety and antimicrobial efficacy of TAF, suggesting that TAF could be a potential antibacterial drug candidate for the treatment of infections caused by multiple drug-resistant S. aureus.

Antivirulence activities of retinoic acids against Staphylococcus aureus

Multidrug-resistant bacteria such as Staphylococcus aureus constitute a global health problem. Gram-positive S. aureus secretes various toxins associated with its pathogenesis, and its biofilm formation plays an important role in antibiotic tolerance and virulence. Hence, we investigated if the metabolites of vitamin A1 might diminish S. aureus biofilm formation and toxin production. Of the three retinoic acids examined, 13-cis-retinoic acid at 10 μg/mL significantly decreased S. aureus biofilm formation without affecting its planktonic cell growth (MIC >400 μg/mL) and also inhibited biofilm formation by Staphylococcus epidermidis (MIC >400 μg/mL), but less affected biofilm formation by a uropathogenic Escherichia coli strain, a Vibrio strain, or a fungal Candida strain. Notably, 13-cis-retinoic acid and all-trans-retinoic acid significantly inhibited the hemolytic activity and staphyloxanthin production by S. aureus. Furthermore, transcriptional analysis disclosed that 13-cis-retinoic acid repressed the expressions of virulence- and biofilm-related genes, such as the two-component arlRS system, α-hemolysin hla, nuclease (nuc1 and nuc2), and psmα (phenol soluble modulins α) in S. aureus. In addition, plant and nematode toxicity assays showed that 13-cis-retinoic acid was only mildly toxic at concentrations many folds higher than its effective antibiofilm concentrations. These findings suggest that metabolites of vitamin A1, particularly 13-cis-retinoic acid, might be useful for suppressing biofilm formation and the virulence characteristics of S. aureus.

Targeting Staphylococcal Cell-Wall Biosynthesis Protein FemX Through Steered Molecular Dynamics and Drug-Repurposing Approach

Staphylococcus aureus-mediated infection is a serious threat in this antimicrobial-resistant world. S. aureus has become a "superbug" by challenging conventional as well as modern treatment strategies. Nowadays, drug repurposing has become a new trend for the discovery of new drug molecules. This study focuses on evaluating FDA-approved drugs that can be repurposed against S. aureus infection. Steered molecular dynamics (SMD) has been performed for Lumacaftor and Olaparib against staphylococcal FemX to understand their binding to the active site. A time-dependent external force or rupture force has been applied to the ligands to calculate the force required to dislocate the ligand from the binding pocket. SMD analysis indicates that Lumacaftor has a high affinity for the substrate binding pocket in comparison to Olaparib. Umbrella sampling exhibits that Lumacaftor possesses a higher free energy barrier to displace it from the ligand-binding site. The bactericidal activity of Lumacaftor and Olaparib has been tested, and it shows that Lumacaftor has moderate activity along with biofilm inhibition potential (MIC value with conc. 128 μg/mL). Pharmacokinetic and toxicology evaluations indicate that Lumacaftor has higher pharmacokinetic potential with lower toxicity. This is the first experimental report where staphylococcal FemX has been targeted for the discovery of new drugs. It is suggested that Lumacaftor may be a potential lead molecule against S. aureus.

Battle royale: Immune response on biofilms – host-pathogen interactions

The research interest of the scientific community in biofilm-forming microorganisms is growing due to the problems caused by their infections affecting humans and animals, mainly because of the difficulty of the host immune system in eradicating these microbial complex communities and the increasing antimicrobial resistance rates worldwide. This review describes the virulence factors and their interaction with the microbial communities of four well-known and highly biofilm-forming pathogens, more exactly, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus spp., and Candida spp. The innate and adaptive immune responses caused by the infection with these microorganisms and their evasion to the host immune system by biofilm formation are discussed in the present work. The relevance of the differences in the expression of certain virulence factors and the immune response in biofilm-associated infections when compared to planktonic infections is usually described as the biofilm architecture protects the pathogen and alters the host immune responses, here we extensively discussed these mechanisms.

In vitro activities of licochalcone A against planktonic cells and biofilm of Enterococcus faecalis

This study aims to evaluate the in vitro antibacterial and anti-biofilm activities of licochalcone A on Enterococcus faecalis and to investigate the possible target genes of licochalcone A in E. faecalis. This study found that licochalcone A had antibacterial activities against E. faecalis, with the MIC50 and MIC90 were 25 μM. Licochalcone A (at 4 × MIC) indicated a rapid bactericidal effect on E. faecalis planktonic cells, and killed more E. faecalis planktonic cells (at least 3-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 2, 4, and 6 h of the time-killing test. Licochalcone A (at 10 × MIC) significantly reduced the production of E. faecalis persister cells (at least 2-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 24, 48, 72, and 96 h of the time-killing test. Licochalcone A (at 1/4 × MIC) significantly inhibited the biofilm formation of E. faecalis. The RNA levels of biofilm formation-related genes, agg, esp, and srtA, markedly decreased when the E. faecalis isolates were treated with licochalcone A at 1/4 × MIC for 6 h. To explore the possible target genes of licochalcone A in E. faecalis, the licochalcone A non-sensitive E. faecalis clones were selected in vitro by induction of wildtype strains for about 140 days under the pressure of licochalcone A, and mutations in the possible target genes were detected by whole-genome sequencing. This study found that there were 11 nucleotide mutations leading to nonsynonymous mutations of 8 amino acids, and among these amino acid mutations, there were 3 mutations located in transcriptional regulator genes (MarR family transcriptional regulator, TetR family transcriptional regulator, and MerR family transcriptional regulator). In conclusion, this study found that licochalcone A had an antibacterial effect on E. faecalis, and significantly inhibited the biofilm formation of E. faecalis at subinhibitory concentrations.