Acquisition of iron from host proteins by the group A streptococcus. Infect. Immun

To identify mammalian iron-binding proteins that can serve as iron sources for Streptococcus pyogenes, the group A streptococcus (GAS), we used a plate assay. Ferritin, hemin, hemoglobin, myoglobin, and catalase can support growth of GAS on iron-depleted medium. However, growth was not detected when iron was provided as iron-saturated transferrin or lactoferrin or bound to cytochrome c. Therefore, it appears that GAS can use the intracellular iron sources available in the human body, which is consistent with its ability to cause tissue destruction during infection. The process of infectious disease as it relates to pathogenic microorganisms depends largely upon the efficiency with which these organisms gain access to the host, colonize, cause pathol-ogy, and disseminate to a new host (9). Colonization involves adherence and multiplication. The latter requires acquisition from the host of nutrients essential for growth, including iron. Little free iron (ca. 10218 M) is present in the human host because most is complexed to proteins, which represent the primary reservoir of iron for pathogenic bacteria (4, 12, 13)