The role of iron in the virulence of the organism Listeria monocytogenes

Abstract

Virulent and avirulent strains of Listeria monocytogenes , a facultative intracellular parasite, were cultured in deferrated media supplemented with varying [micro]g concentrations of ferric iron, supplied either as a free salt or bound to human transferrin. Virulent organisms achieved faster growth rates with higher cell yields than avirulent strains when given identical concentrations of iron. Normal guinea pig serum was determined to be bacteriostatic when used as a culture media for the growth of Listeria. This effect was overcome by saturating the serum transferrin to 95% with iron. There was found a positive correlation in virulence and the ability of the bacteria to utilize transferrin bound iron. In addition it was determined that in vitro production of hemolysin by Listeria is under control of external iron in the growth media.