Characterization of Virulence Factors ofStaphylococcus aureus: Novel Function of Known Virulence Factors That Are Implicated in Activation of Airway Epithelial Proinflammatory Response

Abstract

Airway epithelial cells play a major role in initiating inflammation in response to bacterial pathogens. S. aureus is an important pathogen associated with activation of diverse types of infection characterized by inflammation dominated by polymorphonuclear leukocytes. This bacterium frequently causes lung infection, which is attributed to virulence factors. Many of virulence determinants associated with S. aureus-mediated lung infection have been known for several years. In this paper, we discuss recent advances in our understanding of known virulence factors implicated in pneumonia. We anticipate that better understanding of novel functions of known virulence factors could open the way to regulate inflammatory reactions of the epithelium and to develop effective strategies to treat S. aureus-induced airway diseases.

The Effect of Adding Blood on the Virulence Genes Expression of Staphylococcus aureus in Exponential and Stationary Growth Phase

“…Bacteria in the presence of blood (BHIB), which resembles in vivo conditions, compared with BHI broth, will lead agr regulatory system to increase expression of virulence factors. Thus, a 4-fold increase in hla gene expression was observed, which explained the presence of red blood cells, white blood cells, and platelets that could be targeted by this toxin (1,19). This topic, along with the decrease in the gene expression of spa, indicates the activation of quorum sequencing system by agr in BHI supplemented with 5% sheep blood.…”

“…The ability of these bacteria to cause such severe infections is related to numerous virulence factors that allow these bacteria to adhere to surfaces/tissues, avoid or invade the immune system, and cause harmful toxic effects in the host. The most important factors are secreted hemolysins, toxins, extracellular enzymes, anti-inflammatory peptides, adhesions, and immune evasion mechanisms (1,2).…”

Staphylococcus aureus: Immunopathogenesis and Human Immunity

“…Structures of bacterial cell involved in pathogenesis are: capsule, protein A, and teichoic acid. Also, nearly the the all strains of S. aureus excrete a group of exstracellular products such as exoproteins: nucleases, proteases, lipases, hyaluronidase, and collagenase, as well as exotoxins: α-hemolysin, β-hemolysin, γ-hemolysin, leukocidin, and PantonValentine leukocidin (PVL) (10). Their ability to produce β-lactamases provides an efficient defense against antimicrobial drugs.…”

“…Protein synthesis can influence virulence gene expression, too. Therefore, virulence gene regulators could affect the expression of target genes directly, by binding to their promoters, or indirectly, via other regulators (10). Several global regulatory loci determine the production of S. aureus virulence factors: accessory gene regulator (agr), which controls at least 15 S. aureus products such as extracellular toxins and enzymes: alpha-, beta-, and delta-hemolysin, leucocidin, lipase, hyaluronate lyase, and proteases.…”

“…Cytolytic toxins (Cytolysin) form β-cylindrical pore in the plasma membrane causing a leakage in the cell and thus lyse the target cell (15). S. aureus secretes several cytolysins, including α-hemolysin, β-hemolysin, γ-hemolysin, leukocidin, and Panton-Valentine leukocidin (PVL) (10).…”