Effect of EDDA on the Growth of Streptococcus milleri and Staphylococcus aureus

The effect of EDDA (Ethylenediamin di-o-hydroxyphenylacetic acid), a potent iron chelator, on the growth kinetics of Streptococcus milleri and Staphylococcus aureus was investigated. A bactericidal effect was observed at concentrations up to 20 mM with Staph. aureus whereas the strains of Strep. milleri were unaffected by 20 mM of EDDA showing that Strep. milleri was insensitive to a high molar excess of EDDA to iron indicating either an extraordinarily efficient Fe acquisition system or a low requirement for iron as compared to Staph aureus.