Antibacterial Effect of the Scandium and Indium Complexes of Enterochelin on Escherichia coli

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Abstract
Enterochelin, the Fe chelator produced by serval pathogenic enterobacteria, appears to be an essential metabolite for multiplication within the host, where it transports Fe from the host Fe-binding proteins to the bacteria. Previous work showed that complexes of enterochelin containing either Sc3+ or In3+ exerted a bacteriostatic effect on Klebsiella pneumoniae in serum, while the Sc3+ complex exerted a significant therapeutic effect on mice infected with K. pneumoniae. These observations have now been extended to several pathogenic serotypes of E. coli, including those carrying the K1 antigen or the CoV plasmid. The Sc3+ and In3+ complexes each exert a bacteriostatic effect on these organisms growing in whole serum or in media containing an Fe-binding protein. Evidence is presented that the Sc3+ complex may act as a competitive inhibitor of the Fe3+ complex. In contrast to their effects on K. pneumoniae, sideramines other than enterochelin fail to reverse the bacteriostatic effect of the complex produces a more profound derangement of metabolism in this organism. The Sc3+ complex exerts a significant therapeutic effect on E. coli infections in mice although the In3+ complex is less active.