Gammahemolysin

Gamma-hemolysin is a secreted cytotoxin produced by Staphylococcus aureus, classified among the leukocidin and pore-forming toxins. It is encoded by the hlgABC operon and can involve multiple subunits, notably HlgA, HlgB, and HlgC. The core cytolytic activity is associated with a heteromeric complex formed by HlgA and HlgB on target cell membranes, which assembles into a pore that disrupts ionic gradients and leads to lysis of susceptible cells. HlgC can act as an auxiliary component that modulates activity in some strains.

The toxin targets immune cells such as neutrophils and monocytes, and can affect certain erythrocytes in vitro. By forming membrane pores, gamma-hemolysin contributes to cell death and to the virulence of S. aureus, assisting in tissue damage and immune evasion during invasive infections. Expression of gamma-hemolysin is regulated by the bacteria’s agr quorum-sensing system and is influenced by environmental conditions, with production varying between strains and growth phases.

Laboratory detection of gamma-hemolysin activity can involve functional hemolysis assays on blood-containing media, as well as genetic methods to identify hlgA, hlgB, and hlgC genes in clinical isolates. The toxin is related to other staphylococcal pore-forming toxins, such as alpha-hemolysin and Panton-Valentine leukocidin, and remains a focus of study for understanding pathogenesis and exploring therapeutic targeting.