Epidemiology and Genetics of Hemolysin Formation in Escherichia coli

Abstract

Hemolysins or cytolysins are extracellular toxic proteins that disrupt the membranes of erythrocytes and other differentiated eucaryotic cells.¹ Most hemolysins seem to have little or no effect on procaryotic cells. The hemolytic phenotype is frequently associated with pathogenic strains of a given bacterial species. There is clear evidence for the involvement in pathogenesis for cytolysins in Gram-positive pathogenic bacteria, such as streptolysins produced by Streptococcus pyogenes, α-, β-, γ- and δ-toxins from Staphylococcus aureus, θ-toxin from Clostridium perfringens, listeriolysins from Listeria monocytogenes and others.These toxins all of which can be considered as hemolysins disrupt eucaryotic membranes by different modes of action, which are only partially understood. Whereas some cytolysins act as enzymes, like the staphylococcal 3-toxin which is a sphingomyelinase,² others like the “SH-activated cytotoxins” including streptolysin O, C. perfringens θ-toxin, cereolysin (Bacillus cereus) and listeriolysin disrupt eucaryotic membranes by a non-enzymatic mode of action, using probably cholesterol as receptor.³