Identification of a new iron-regulated virulence gene, ireA, in an extraintestinal pathogenic isolate of Escherichia coli.
Our laboratory is studying an extraintestinal pathogenic isolate of Escherichia coli (CP9) as a model pathogen. We have been using human urine, ascites, and blood ex vivo to identify genes with increased expression in these media relative to expression in Luria-Bertani (LB) broth. Such genes may represent new or unrecognized virulence traits. In this study, we report the identification of a new gene, ireA (iron-responsive element). This gene has an open reading frame of 2,049 nucleotides, and its peptide has a molecular mass of 75.3 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its expression is increased a mean of 3.6-fold in human urine, 16.2-fold in human ascites, and 6.6-fold in human blood relative to expression in LB medium, and it is Fe repressible. IreA also exhibits peptide similarities (48 to 56%) to previously identified proteins that function as siderophore receptors, suggesting that IreA is involved in iron acquisition. PCR-based analysis of ireA's phylogenetic distribution detected ireA in none (0%) of 14 fecal isolates that represented probable commensal strains, but in 13 (26%) of 50 random urine and blood clinical isolates (P = 0.05) and in 5 (100%) of 5 representatives of the J96-like, clonal group of which CP9 is a member (P < 0.001). In a mouse urinary tract infection model, the presence of ireA contributed significantly to CP9's ability to colonize the bladder (P < 0.02), evidence that IreA is a urovirulence factor. Taken together, these findings demonstrate that ireA encodes a new virulence factor, which is likely involved in Fe acquisition.
Russo
T A
TA
Department of Medicine, University at Buffalo, Buffalo, New York 14214, USA. trusso@acsu.buffalo.edu
Carlino
U B
UB
Johnson
J R
JR
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D003470:Culture Media; D004269:DNA, Bacterial; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity; D029968:Escherichia coli Proteins; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D014552:Urinary Tract Infections / Q000378:metabolism / Q000382:microbiology; D014774:Virulence
D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C437328:IreA protein, E coli; D007501:Iron