title: Aggregation substance promotes colonic mucosal invasion of Enterococcus faecalis in an ex vivo model.
abstract: BACKGROUND
  Bacterial translocation through the gastrointestinal tract is the crucial step in the pathogenesis of intraabdominal infections. We assessed whether aggregation substance (AS), a bacterial adhesin and virulence factor of Enterococcus faecalis, promotes bacterial translocation and colonic mucosal invasion in an ex vivo experiment.
  
  
  METHODS
  Colonic mucosa of male Wistar rats was placed in a modified Ussing system. The mucosal side of the chamber was filled with a suspension of E. faecalis OG1X:pAM721 (AS-positive) or E. faecalis OG1X (AS-negative). The serosal side was filled with sterile Dulbecco's modified Eagle's medium. For assessment of colonic mucosal invasion the mucosal side was incubated for 2.5 h with a suspension of AS-positive or AS-negative enterococci. After being washed, a solution of gentamicin and penicillin G in tissue culture medium was added on both sides in order to kill extracellular bacteria. Subsequently, the mucosa was removed from the system, washed, lysed with Triton X-100, and homogenized. Viable intramural bacteria were quantified by plating serial dilutions of the homogenate on Todd-Hewitt broth agar plates. To quantify bacterial translocation samples which were taken at various time points from the serosal side were plated on Todd-Hewitt broth agar plates and colony forming units (CFU) were determined.
  
  
  RESULTS
  Invasion of the AS-positive E. faecalis strain OG1X:pAM721 into the colonic mucosa was significantly higher than invasion rates of the AS-negative strain OG1X (2.88 log(10) CFU/ml vs 1.73 log(10) CFU/ml; P = 0.02). However, none of the tested strains was found to translocate from the mucosal to the serosal side within the incubation time of 4 h.
  
  
  CONCLUSIONS
  The aggregation substance promotes invasion of E. faecalis into colonic mucosa.
authors.affiliation: Department of General Surgery, University of Ulm, Ulm, 89075, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Isenmann
authors.forename: M
authors.initials: M
authors.lastname: Schwarz
authors.forename: E
authors.initials: E
authors.lastname: Rozdzinski
authors.forename: R
authors.initials: R
authors.lastname: Marre
authors.forename: H G
authors.initials: HG
authors.lastname: Beger
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology*; D018988:Bacterial Translocation / Q000187:drug effects*; D003106:Colon / Q000382:microbiology* / Q000473:pathology; D013293:Enterococcus faecalis / Q000502:physiology*; D007413:Intestinal Mucosa / Q000382:microbiology* / Q000473:pathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012486:Salmonella typhimurium / Q000502:physiology; D012724:Sex Attractants / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D012724:Sex Attractants; C065937:aggregation substance, Enterococcus faecalis