Iha from an Escherichia coli urinary tract infection outbreak clonal group A strain is expressed in vivo in the mouse urinary tract and functions as a catecholate siderophore receptor.
Virulence factors of pathogenic Escherichia coli belonging to a recently emerged and disseminated clonal group associated with urinary tract infection (UTI), provisionally designated clonal group A (CGA), have not been experimentally investigated. We used a mouse model of ascending UTI with CGA member strain UCB34 in order to identify genes of CGA that contribute to UTI. iha was identified to be expressed by strain UCB34 in the mouse kidney using selective capture of transcribed sequences. iha from strain UCB34 demonstrated a siderophore receptor phenotype when cloned in a catecholate siderophore receptor-negative E. coli K-12 strain, as shown by growth promotion experiments and uptake of (55)Fe complexed to enterobactin or its linear 2, 3-dihydroxybenzoylserine (DHBS) siderophore derivatives. Siderophore-mediated growth promotion by Iha was TonB dependent. Growth and iron uptake were more marked with linear DHBS derivatives than with purified enterobactin. The reported phenotype of adherence to epithelial cells conferred by expressing iha from a multicopy cloning vector in a poorly adherent E. coli K-12 host strain was confirmed to be specific to iha, in comparison with other siderophore receptor genes. iha expression was regulated by the ferric uptake regulator Fur and by iron availability, as shown by real-time reverse transcriptase PCR. In a competitive infection experiment using the mouse UTI model, wild-type strain UCB34 significantly outcompeted an isogenic iha null mutant. Iha thus represents a Fur-regulated catecholate siderophore receptor that, uniquely, exhibits an adherence-enhancing phenotype and is the first described urovirulence factor identified in a CGA strain.
Léveillé
Simon
S
INRS-Institut Armand-Frappier, 531 boul. des Prairies, Laval H7V 1B7, Québec, Canada.
Caza
Mélissa
M
Johnson
James R
JR
Clabots
Connie
C
Sabri
Mourad
M
Dozois
Charles M
CM
D000328:Adult; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D001426:Bacterial Proteins / Q000502:physiology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000187:drug effects / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000502:physiology*; D005260:Female; D006801:Humans; D007501:Iron / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology; D051379:Mice; D008808:Mice, Inbred CBA; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology; D014552:Urinary Tract Infections / Q000382:microbiology*; D014774:Virulence
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; C035902:siderophore receptors; C489181:tonB protein, E coli; D007501:Iron