title: Adherent-invasive Escherichia coli (AIEC) in pediatric Crohn's disease patients: phenotypic and genetic pathogenic features.
abstract: BACKGROUND
  Adherent-invasive Escherichia coli (AIEC) have been implicated in the ethiopathogenesis of Crohn's disease (CD). In this study, we analyzed a collection of intestinal mucosa-associated E. coli isolates, presenting AIEC phenotypes, isolated from biopsies of CD pediatric patients and non-inflammatory bowel diseases (IBD) controls, in order to investigate their genetic and phenotypic pathogenic features.
  
  
  RESULTS
  A total of 616 E. coli isolates from biopsies of four pediatric CD patients and of four non-IBD controls were collected and individually analyzed. For AIEC identification, adherent isolates were assayed for invasiveness, and the capacity of the adhesive-invasive isolates to survive and replicate intracellularly was determined over macrophages J774. In this way we identified 36 AIEC-like isolates. Interestingly, their relative abundance was significantly higher in CD patients (10%; 31/308) than in non-IBD controls (1%; 5/308) (χ2 = 38.96 p < 0.001). Furthermore pulsed field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) techniques were applied to analyze the clonality of the 36 AIEC-like isolates. The results obtained allowed us to identify 27 distinct genotypes (22 from CD patients and 5 from non-IBD controls). As for the AIEC prototype strain LF82, all 27 AIEC genotypes presented an aggregative pattern of adherence (AA) that was inhibited by D-mannose, indicating that adhesiveness of AIEC is likely mediated by type 1 pili. PCR analisys was used to investigate presence of virulence genes. The results indicated that among the 27 AIEC isolates, the incidence of genes encoding virulence factors K1 (χ2 = 6.167 P = 0.013), kpsMT II (χ2 = 6.167 P = 0.013), fyuA (χ2 = 6.167 P = 0.013), and ibeA (χ2 = 8.867 P = 0.003) was significantly higher among AIEC strains isolated from CD patients than non-IBD controls.
  
  
  CONCLUSIONS
  The identification of AIEC strains in both CD and non-IBD controls, confirmed the "pathobiont" nature of AIEC strains. The finding that AIEC-like isolates were more abundant in CD patients, indicates that a close association of these strains with CD may also exists in pediatric patients.
authors.affiliation: Department of Public Health and Infectious Diseases, 'Sapienza' University of Rome, Rome, Italy. mariapia.conte@uniroma1.it.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Conte
authors.forename: Catia
authors.initials: C
authors.lastname: Longhi
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Marazzato
authors.forename: Antonietta Lucia
authors.initials: AL
authors.lastname: Conte
authors.forename: Marta
authors.initials: M
authors.lastname: Aleandri
authors.forename: Maria Stefania
authors.initials: MS
authors.lastname: Lepanto
authors.forename: Carlo
authors.initials: C
authors.lastname: Zagaglia
authors.forename: Mauro
authors.initials: M
authors.lastname: Nicoletti
authors.forename: Marina
authors.initials: M
authors.lastname: Aloi
authors.forename: Valentina
authors.initials: V
authors.lastname: Totino
authors.forename: Anna Teresa
authors.initials: AT
authors.lastname: Palamara
authors.forename: Serena
authors.initials: S
authors.lastname: Schippa
mesh_terms: D000293:Adolescent; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D001706:Biopsy; D018938:Caco-2 Cells; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003424:Crohn Disease / Q000175:diagnosis / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000175:diagnosis / Q000382:microbiology*; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007082:Ileum / Q000382:microbiology* / Q000473:pathology; D007413:Intestinal Mucosa / Q000382:microbiology* / Q000473:pathology; D008264:Macrophages / Q000382:microbiology; D008297:Male; D051379:Mice; D010641:Phenotype; D010802:Phylogeny; D012307:Risk Factors; D014774:Virulence / Q000235:genetics