Description_x000D_ Application_x000D_ α-Hemolysin was used in a study to test the efflux pump and haemolysin activity of Escherichia coli of dairy origin. It was also used to test its adaptation to benzalkonium chloride and the effect of ciprofloxacin on biofilm formation._x000D_ Biochem/physiol Actions_x000D_ α-Hemolysin is a 33 kDa extracellular protein secreted by most strains of pathogenic Staphylococcus aureus. It is selectively hemolytic and has a marked preference for rabbit red blood cells. It induces dermonecrosis, spastic muscle paralysis, and it is lethal for laboratory animals. The toxin must be in the monomeric form to initially bind to a membrane and specific receptors are not required for binding. Upon binding to biological membranes and/or artificial membranes, self-oligomerization occurs, resulting in ring structures (hexameric aggregates) believed to represent transmembrane pores, which are permeable to ions and small metabolites._x000D_ It is thought that α-hemolysin stimulates cellular phospholipases and induces a Ca2+ influx that can result in membrane disruption, leakage of cytoplasmic components, impaired membrane permeability, and osmotic lysis of the cells._x000D_ Packaging_x000D_ Package size based on protein content_x000D_ Unit Definition_x000D_ One hemolytic unit will cause 50% lysis of a 1% suspension of rabbit red blood cells in phosphate buffered saline, pH 7.0, containing 1% bovine serum albumin after 30 min at 37 °C followed by refrigeration for 30 min at 4 °C.