staphyloxanthin and Hemolysis

Staphylococcus aureus nosocomial infections with a high mortality rate in human and animals have been reported to associate with bacterial biofilm formation, along with the secretion of numerous virulence factors. Therefore, the inhibition of biofilm formation and attenuation of virulence determinants are considered as a promising solution to combat the spread of S. aureus infections. Modern trends in antibiofilm therapies have opted for the active agents that are biocompatible, biodegradable, non-toxic and cost-effective. Owning the aforementioned properties, chitosan, a natural N-acetylated carbohydrate biopolymer derived from chitin, has been favorably employed. Recently, the chitosan structure has been chemically modified into Chitooligosaccharides (COS) to overcome its limited solubility in water, thus widening chitosan applications in modern antibiofilm research. In the present study, we have investigated the antibacterial, antibiofilm and anti-virulence activities against S. aureus of COS of different molecular weights dissolved in neutral water.. The study of bactericidal activity was performed using the micro-dilution method while the biofilm inhibition assay was performed using crystal-violet staining method and confirmed by scanning electron microscopic analysis. The inhibition of amyloid protein production was confirmed by Congo Red staining.. Results showed that low molecular weight COS exhibited bactericidal activity and reduced the bacterial amylogenesis, hemolytic activity as well as H. Reducing the molecular weight of chitosan in the form of COS has become an effective strategy to maintain chitosan biological activity while improving its water solubility. The low molecular weight COS investigated in this study have effectively performed antibacterial, antibiofilm and antivirulence properties against S. aureus.

Topics: Amyloidogenic Proteins; Animals; Anti-Bacterial Agents; Biofilms; Cells, Cultured; Chitin; Chitosan; Erythrocytes; Hemolysin Factors; Hemolysis; Humans; Hydrogen Peroxide; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Oligosaccharides; Staphylococcus aureus; Virulence; Xanthophylls

Staphylococcus aureus is an opportunistic pathogen related to a variety of life-threatening infections but for which antimicrobial resistance is liming the treatment options. We report here that myricetin, but not its glycosylated form, can remarkably decrease the production of several S. aureus virulence factors, including adhesion, biofilm formation, hemolysis and staphyloxanthin production, without interfering with growth. Myricetin affects both surface proteins and secreted proteins which indicate that its action is unrelated to inhibition of the agr quorum sensing system. Analysis of virulence related gene expression and computational simulations of pivotal proteins involved in pathogenesis demonstrate that myricetin downregulates the saeR global regulator and interacts with sortase A and α-hemolysin. Furthermore, Myr confers a significant degree of protection against staphylococcal infection in the Galleria mellonella model. The present findings reveal the potential of Myr as an alternative multi-target antivirulence candidate to control S. aureus pathogenicity.

Topics: Animals; Bacterial Adhesion; Biofilms; Erythrocytes; Extracellular Matrix Proteins; Flavonoids; Gene Expression Profiling; Hemolysis; Models, Molecular; Moths; Protective Agents; Protein Binding; Protein Conformation; Staphylococcal Infections; Staphylococcus aureus; Structure-Activity Relationship; Virulence Factors; Xanthophylls

Staphylococcus aureus is a major human pathogen and emergence of antibiotic resistance in clinical staphylococcal isolates raises concerns about our ability to control these infections. Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus. MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress. In the S. aureus chromosome, there are three msrA genes (msrA1, msrA2 and msrA3) and one msrB gene. To understand the precise physiological roles of Msr proteins in S. aureus, mutations in msrA1, msrA2 and msrA3 and msrB genes were created by site-directed mutagenesis. These mutants were combined to create a triple msrA (msrA1, msrA2 and msrA3) and a quadruple msrAB (msrA1, msrA2, msrA3, msrB) mutant. These mutants were used to determine the roles of Msr proteins in staphylococcal growth, antibiotic resistance, adherence to human lung epithelial cells, pigment production, and survival in mice relative to the wild-type strains. MsrA1-deficient strains were sensitive to oxidative stress conditions, less pigmented and less adherent to human lung epithelial cells, and showed reduced survival in mouse tissues. In contrast, MsrB-deficient strains were resistant to oxidants and were highly pigmented. Lack of MsrA2 and MsrA3 caused no apparent growth defect in S. aureus. In complementation experiments with the triple and quadruple mutants, it was MsrA1 and not MsrB that was determined to be critical for adherence and phagocytic resistance of S. aureus. Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

Topics: Animals; Anti-Bacterial Agents; Bacterial Adhesion; Cell Wall; Disease Models, Animal; Enzyme Activation; Hemolysis; Humans; Methionine Sulfoxide Reductases; Mice; Microbial Sensitivity Tests; Mutation; Oxidants; Oxidative Stress; Phagocytosis; Protein Transport; Staphylococcal Infections; Staphylococcal Protein A; Staphylococcus aureus; Xanthophylls

One of the most common pathogens causing musculoskeletal infections remains Staphylococcus aureus. The aim of this multicentre study was to perform a phenotypic and genotypic characterisation of clinical S. aureus isolates recovered from musculoskeletal infections and to investigate differences between isolates cultured from Orthopaedic Implant Related Infections (OIRI) and those from Non-Implant Related Infections (NIRI). OIRI were further differentiated in two groups: Fracture Fixation-Device Infections (FFI) and Prosthetic Joint Infections (PJI). Three-hundred and five S. aureus strains were collected from 4 different Swiss and 2 French hospitals (FFI, n=112; PJI, n=105; NIRI, n=88). NIRI cases were composed of 27 Osteomyelitis (OM), 23 Diabetic Foot Infections (DFI), 27 Soft Tissue Infections (STI) and 11 postoperative Spinal Infections (SI). All isolates were tested for their ability to form biofilm, to produce staphyloxanthin and their haemolytic activity. They were typed by agr (accessory gene regulator) group, spa type and screened by PCR for the presence of genes of the most relevant virulence factors such as MSCRAMMs, Panton Valentine Leukotoxin (PVL), enterotoxins, exotoxins and toxic shock syndrome toxin. Overall, methicillin susceptible S. aureus (MSSA) was more prevalent than methicillin resistant S. aureus (MRSA) in this collection. The OIRI group trended towards a higher incidence of MRSA, gentamicin resistance and haemolysis activity than the NIRI group. Within the OIRI group, PJI isolates were more frequently strong biofilm formers than isolates from the FFI group. A statistically significant difference was observed between OIRI and NIRI isolates for the sdrE gene, the cna gene, the clfA gene and the bbp gene. Certain spa types (t230 and t041) with a specific genetic virulence pattern were only found in isolates cultured from OIRI. In conclusion, our study highlights significant trends regarding the virulence requirements displayed by S. aureus isolates associated with implant related infections in comparison to non-implant related infections. However, future studies including whole genome sequencing will be required to further examine genomic differences among the different infection cases.

Topics: Biofilms; Diabetic Foot; France; Genes, Bacterial; Genotype; Hemolysis; Hospitals; Humans; Musculoskeletal Diseases; Osteomyelitis; Phenotype; Polymerase Chain Reaction; Prosthesis-Related Infections; Retrospective Studies; Soft Tissue Infections; Staphylococcal Infections; Staphylococcus aureus; Switzerland; Virulence Factors; Xanthophylls

Staphylococcus aureus is a leading cause of nosocomial infections due to its resistance to diverse antibiotics. This bacterium produces a large number of extracellular virulence factors that are closely associated with specific diseases. In this study, diverse plant flavonoids were investigated to identify a novel anti-virulence compound against two S. aureus strains. Flavone, a backbone compound of flavonoids, at subinhibitory concentration (50 μg/mL), markedly reduced the production of staphyloxanthin and α-hemolysin. This staphyloxanthin reduction rendered the S. aureus cells 100 times more vulnerable to hydrogen peroxide in the presence of flavone. In addition, flavone significantly decreased the hemolysis of human red blood by S. aureus, and the transcriptional level of α-hemolysin gene hla and a global regulator gene sae in S. aureus cells. This finding supported the usefulness of flavone as a potential antivirulence agent against antibiotic-resistant S. aureus.

Topics: Bacterial Toxins; Flavones; Hemolysin Proteins; Hemolysis; Humans; Staphylococcus aureus; Virulence; Virulence Factors; Xanthophylls