Role of α-Hemolysin for the in vitro Phagocytosis and Intracellular Killing of Escherichia coli

Abstract

The role of α-hemolysin for the elimination of Escherichia coli by phagocytes in vitro was investigated using sets of isogenic strains which included wild-type α-hemolytic strains, derived strains with a reduced production of α-hemolysin and derived nonhemolytic strains. Phagocytosis and intracellular killing of the bacteria by human blood granulocytes or monocytes were measured using growth inhibition techniques. α-hemolytic strains were phagocytosed and killed to a lesser extent than isogenic strains with a reduced production of α-hemolysin and isogenic nonhemolytic strains. The results obtained with granulocytes were similar to those obtained with monocytes although the elimination of bacteria by monocytes was less than that by granulocytes. These results strongly suggest that production of α-hemolysin is a means by which E. coli counteracts the activity of phagocytes by injuring these cells with the toxin.