Expression of high affinity iron uptake systems by clinical isolates ofKlebsiella

Seventeen isolates of Klebsiella aerogenes, K. pneumoniae, K. oxytocum and K. edwardsii were examined for their ability to express iron-regulated outer membrane proteins (IROMPs) and high affinity iron-chelating agents (siderophores). In response to iron deprivation, all strains induced at least 4 IROMPs in the approximate Mr range 70 000–85 000 and the phenolate siderophore enterobactin. Six strains also produced the hydroxamate siderophore aerobactin. The Klebsiella enterobactin receptor was identified as an 81 000 Mr iron-repressible outer membrane (OM) protein which appears to be highly conserved and shows considerable antigenic homology with that of Escherichia coli.