Evidence for non-siderophore-mediated acquisition of transferrin-bound iron by Pasteurella multocida.

Two clinical isolates of Pasteurella multocida associated with bovine pneumonia were examined for iron acquisition. Both isolates were capable of obtaining iron for growth from bovine but not from human, avian, equine or porcine transferrin. This correlated with specific binding of bovine transferrin by iron-limited cells or isolated membranes. No siderophore was detected in the strains by a general screening assay. In response to iron-limited conditions, a number of high molecular mass iron-regulated outer membrane proteins were produced including an 82 kDa receptor protein which was affinity isolated with biotinylated transferrin. In contrast, avian strains of P. multocida could not use transferrin-bound for growth and did not express either transferrin binding activity or the 82 kDa receptor protein.