Comprehensive evaluation and analysis of the salinity stress response mechanisms based on transcriptome and metabolome of Staphylococcus aureus

Phytochemical-Loaded Thermo-responsive Liposome for Synergistic Treatment of Methicillin-Resistant Staphylococcus aureus Infection

The ever-increasing emergence and prevalence of multidrug-resistant bacteria accelerate the desire for the development of new antibacterial strategies. Although antibacterial phytochemicals are a promising approach for long-term treatment of resistant bacteria, their low antibacterial activity and poor solubility hinder their practical applications. Here, the natural antibacterial compound sanguinarine (SG) together with gallic acid-ferrous coordination nanoparticles (GA-Fe(II) NPs) was encapsulated in a near-infrared (NIR)-activated thermo-responsive liposome. By virtue of the photothermal effect of GA-Fe(II) NPs, the nanoplatform released SG on demand upon NIR irradiation. Additionally, the heat can boost the Fenton reaction triggered by GA-Fe(II) NPs to generate hydroxyl radicals and perform sterilization. By coupling with photothermal therapy, chemodynamic therapy, and SG-based pharmacotherapy, the platform showed enhanced antibacterial efficiency and an antibiofilm effect toward methicillin-resistant Staphylococcus aureus and reduced the risk of developing new bacterial resistance. This antibacterial system displayed excellent antibacterial activity in a methicillin-resistant S. aureus-caused skin abscess, demonstrating its potential clinical application. Moreover, transcription analysis clarified that the platform achieved a synergistic antibacterial effect by attacking the cell membrane, inducing energy metabolism disorder, inhibiting nucleic acid synthesis, etc. The developed NIR-controlled phytochemical-loaded platform offers new possibilities for killing antibiotic-resistant bacteria and avoiding bacterial resistance, making it contributory in the fields of anti-infective therapy and precision medicine.

Targeting membrane integrity and imidazoleglycerol-phosphate dehydratase: Sanguinarine multifaceted approach against Staphylococcus aureus biofilms

BACKGROUND

Staphylococcus aureus is an opportunistic pathogen capable of readily forming biofilms, which can result in life-threatening infections involving different organs. Sanguinarine are benzo[c]phenanthridine alkaloids extracted from the Sanguinaria canadensis L. (Papaveraceae), which have a wide range of biological activities. Previous reports have shown that sanguinarine is able to induce an elevation of ROS to exert an anti-S. aureus effect. Nevertheless, the specific mechanism of action of sanguinarine against S. aureus biofilms remains unexplored.

PURPOSE

The objective of this study was to elucidate the target site of sanguinarine in S. aureus, as well as to investigate its mechanism of antimicrobial action and its interference with biofilm formation. Additionally, the study aimed to provide further evidence supporting the use of sanguinarine as an alternative to traditional antibiotics.

METHODS

Initially, we assessed the in vitro anti-S. aureus properties of sanguinarine through a series of methodologies, including MIC assays, time-dependent assays, and resistance development studies. Secondly, we explored the antimicrobial mechanism of sanguinarine using TEM, membrane permeability assays, and membrane fluidity assays. Subsequently, the mechanism by which sanguinarine interferes with S. aureus biofilm formation was preliminarily analyzed in vitro. Additionally, the interaction between sanguinarine and imidazoleglycerol-phosphate dehydratase (IGPD) was investigated using bio-layer interferometry assays, circular dichroism spectroscopy, molecular docking, and site-directed mutagenesis to further elucidate the role of sanguinarine in biofilm disruption. Finally, the therapeutic efficacy of sanguinarine was evaluated in vivo using mouse models of biofilm and bacteremia.

RESULTS

Herein, sanguinarine demonstrated notable antimicrobial properties and interfering effects on biofilm formation. Mechanistic investigations revealed that sanguinarine exerts its antimicrobial action by dissipating the proton motive force in bacteria and compromising the integrity and functionality of the cytoplasmic membrane. Furthermore, sanguinarine was found to regulate IGPD expression and inhibit L-histidine synthesis, thereby interfering S. aureus biofilm formation. Consequently, due to its polypharmacological effect, sanguinarine significantly reduced the S. aureus load in mouse organs and the formation of biofilm on the surface of implants in vivo without any resistance.

CONCLUSIONS

In this study, we demonstrated that sanguinarine can exert antibacterial and interfere with biofilm formation by disrupting the cell membrane of S. aureus and targeting IGPD. These findings suggest that sanguinarine holds potential for further development as a novel antibiotic to combat biofilm-associated infections.

Antibacterial Mechanism of 2R,3R-Dihydromyricetin Against Staphylococcus aureus: Deciphering Inhibitory Effect on Biofilm and Virulence Based on Transcriptomic and Proteomic Analyses

Staphylococcus aureus is a major foodborne pathogen that leads to various diseases due to its biofilm and virulence factors. This study aimed to investigate the inhibitory effect of 2R,3R-dihydromyricetin (DMY), a natural flavonoid compound, on the biofilm formation and virulence of S. aureus, and to explore the mode of action using transcriptomic and proteomic analyses. Microscopic observation revealed that DMY could remarkably inhibit the biofilm formation by S. aureus, leading to a collapse on the biofilm architecture and a decrease in viability of biofilm cell. Moreover, the hemolytic activity of S. aureus was reduced to 32.7% after treatment with subinhibitory concentration of DMY (p < 0.01). Bioinformation analysis based on RNA-sequencing and proteomic profiling revealed that DMY induced 262 differentially expressed genes and 669 differentially expressed proteins (p < 0.05). Many downregulated genes and proteins related to surface proteins were involved in biofilm formation, including clumping factor A (ClfA), iron-regulated surface determinants (IsdA, IsdB, and IsdC), fibrinogen-binding proteins (FnbA, FnbB), and serine protease. Meanwhile, DMY regulated a wide range of genes and proteins enriched in bacterial pathogenesis, cell envelope, amino acid metabolism, purine and pyrimidine metabolism, and pyruvate metabolism. These findings suggest that DMY targets S. aureus through multifarious mechanisms, and especially prompt that interference of surface proteins in cell envelope would lead to attenuation of biofilm and virulence.

Metabolomics-based response of Salmonella to desiccation stress and skimmed milk powder storage

The strong survival ability of Salmonella in low-moisture foods (LMFs) has been of public concern, and is considered a threat to people's health. Recently, the development of omics technology has promoted research on the molecular mechanisms of the desiccation stress response of pathogenic bacteria. However, multiple analytical aspects related to their physiological characteristics remain unclear. We explored the physiological metabolism changes of S. enterica Enteritidis exposed to a 24 h-desiccation treatment and a subsequent 3-month desiccation storage in skimmed milk powder (SMP) with an approach of gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-Q Exactive-mass spectrometry (UPLC-QE-MS). A total of 8,292 peaks were extracted, of which 381 were detected by GC-MS and 7,911 peaks were identified by LC-MS/MS, respectively. Through analyses of differentially expressed metabolites (DEMs) and key pathways, a total of 58 DEMs emerged from the 24 h-desiccation treatment, which exhibited the highest relevance for five metabolic pathways, involving glycine, serine, and threonine metabolism, pyrimidine metabolism, purine metabolism, vitamin B6 metabolism, and pentose phosphate pathway. After 3-month SMP storage, 120 DEMs were identified, which were related to several regulatory pathways including arginine and proline metabolism, serine and threonine metabolism, β-alanine metabolism, glycerolipid metabolism, and glycolysis. The analyses of key enzyme activities of XOD, PK, and G6PDH and ATP content provided further evidence that supported the metabolic responses such as nucleic acid degradation, glycolysis, and ATP production played an important role in Salmonella's adaptation to desiccation stress. This study enables a better understanding of metabolomics-based responses of Salmonella at the initial stage of desiccation stress and the following long-term adaptive stage. Meanwhile, the identified discriminative metabolic pathways may serve as potentially useful targets in developing strategies for the control and prevention of desiccation-adapted Salmonella in LMFs.

The Response and Survival Mechanisms of Staphylococcus aureus under High Salinity Stress in Salted Foods

Staphylococcus aureus (S. aureus) has a strong tolerance to high salt stress. It is a major reason as to why the contamination of S. aureus in salted food cannot be eradicated. To elucidate its response and survival mechanisms, changes in the morphology, biofilm formation, virulence, transcriptome, and metabolome of S. aureus were investigated. IsaA positively regulates and participates in the formation of biofilm. Virulence was downregulated to reduce the depletion of nonessential cellular functions. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The MtsABC transport system was downregulated to reduce ion transport and signaling. Aminoacyl-tRNA biosynthesis was upregulated to improve cellular homeostasis. The betaine biosynthesis pathway was upregulated to protect the active structure of proteins and nucleic acids. Within a 10% NaCl concentration, the L-proline content was upregulated to increase osmotic stability. In addition, 20 hub genes were identified through an interaction analysis. The findings provide theoretical support for the prevention and control of salt-tolerant bacteria in salted foods.