Klebsiella oxytoca as a potential agent of acute colitis

A322 AGA ABSTRACTS

1758 THE EFFECTS OF RACECADOTRIL ON ESCHERICIA COU HEAT LABILE TOXIN (LT) INDUCED INTESTINAL SECRE· TION. Matthew R. Banks, Monica Bose, Matthew P. Lunn, Michael J. Farthing, St Bartholomew's and The Royal London Sch of Medicine, London, United Kingdom. We investigated the effects of the enkephalinase inhibitor racecadotril, on Eschericia coli heat labile toxin-induced intestinal secretion. Opioids appear to inhibit intestinal secretion via delta receptors in the gastrointestinal tract and possibly the CNS. Endogenous opioids such as methionine- and leucine-enkephalin are metabolised by enkephalinase (membrane metalloendopeptidase) and aminopeptidase. Racecadotril through enkephalinase antagonism is therefore thought to act by increasing the bioavailability of the endogenous enkephalins, thereby promoting absorption. Previous studies have shown racecadotril to reduce secretion induced by cholera toxin in humans and animals, and also limit experimental and infectious diarrhoea in humans. Our aims were to establish whether the inhibitory action ofracecadotril is also applicable to LT-induced secretion. Methods: Male Wistar rats were pre-treated with intrajejunal racecadotril (2Orng/kg; n= 16), or vehicle (n=7), 30 min before a 2 h incubation with LT (50/Lg/ kg) in a 20cm jejunal loop. The loop was then perfused with a plasma electrolyte solution (0.5mllmin) containing 14C-polythylene glycol (PEG) as a non-absorbable volume marker. After an initial 30min period of perfusion, three 20min fluid collections were used to calculate the net water and chloride flux, and steady-state was confirmed by less than 10% variability. Results: We found that Lf-induced hypersecretion was significantly reduced by intrajejunal racecadotril. Net water flux was reduced from -99.9±38 /Lllminlg to -38±28.3 /Lllminlg(P=0.02; mean±SD; Mann-Whitney U test) and the net chloride flux was reduced from -19.85±5.49 /Lmollminlg to -8.31±5.44 /Lmollminlg (P=0.OOO5) Conclusions: This study demonstrates that racecadotril inhibits intestinal fluid and electrolyte secretion induced by LT; probably by the protection of endogenous enkephalins. More studies are warranted to evaluate the effects of racecadotril on other secretagogues and to define the pathways involved.

1759 KLEBSIELLA OXYTOCA AS A POTENTIAL AGENT OF ACUTE COLITIS. Laurent Beaugerie, Mikaela Metz, Frederic Barbut, Guy Bellaiche, Yoram Bouhnik, Marie-Pierre Le Pennec, Nicolas Delas, Jean-Claude Petit, The Infectious Colitis Study Group, Gastroenterology. Saint-Antoine Univ, Paris. France; Microbiology, Regensburg, Germany; Microbiology, SaintAntoine Univ, Paris, France; Gastroenteroloy, Aulnay, France; Lariboisiere Univ Hosp, Paris, France; Microbiology, Aulnay, France; Gastroenterology, Montfermeil, France; Saint-Antoine Univ, Paris. France. Background: Klebsiella oxytoca (KO) has been isolated from stools and colonic biopsies of some of the patients with Clostridium difficile (CD)negative antibiotic-associated haemorrhagic colitis (AAHC), but the pathogenic role of the bacteria is not definitively established. Aims: To investigate the role of KO in a prospective series of patients with acute colitis (AC), and to test the cytotoxicity of the strains in healthy carriers and in patients with AAHC. Methods: Ninety-three patients with acute colitis in the area of Paris were studied. Colonic biopsies and a sample of colonic fluid were cultured on selective media for 7 well-established pathogens and KO. The KO strains isolated in this series and 105 additional strains from healthy carriers (n=90) or patients with CD-negative AAHC (n=15) were tested for cytotoxicity using Hep-Z cell culture assay. Results: Fourty-two established bacteria (Salmonella (n= 16), CD (n= 15), Shigella (n=7), Campylobacter (n=4)) were isolated in 41 patients (52%) of the prospective series. One coinfection Campylobacter-CD was observed. KO was isolated in association with Shigella in one patient, and alone in 7 patients. including 2 patients with AAHC. The presence of KO was more frequent in patients without established pathogenic bacteria (p=0.05). KO strains were found cytotoxic in 47%, 75%, and 82% of the healthy carriers and the patients with AC or AAHC. respectively. The rate of cytotoxic strains was higher in patients with AAHC than in healthy carriers (p=0.002). Conclusions: Our results: a) strengthen the hypothesis that KO is one of the agents of AAHC; b) suggest that KO could also be involved in some cases of AC negative for established bacterial pathogens and not related to antibiotics.

1760 EVALUATION OF ANTIBIOTIC THERAPY IN A RABBIT MODEL OF SHIGA TOXIN·PRODUCING E.COU (STEC) INFEC· TION: NO EVIDENCE FOR ADVERSE EFFECTS. Laura A. Johnson, Edgar C. Boedeker, Univ of Maryland, Baltimore, MD. Currently there is no effective treatment for infection with the Shiga toxin (Stxj-producing Eicoli strains which induce hemorrhagic colitis and hemolytic-uremic syndrome (HUS). Antibiotic therapy is currently not recommended for STEC infections since some clinical studies suggest poor outcomes for patients treated with antibiotics, and in vitro studies demonstrate increased toxin release from STEC strains cultured with antibiotics below their minimum inhibitory concentrations. In order to determine whether administration of antibiotics would improve, or adversely alter. the course of STEC infection, we carried out studies with Trimethoprimsulfamethoxasole (TMS) in an animal model of STEC: RDEC-HI9A infection of rabbits. Animals were challenged with E.coli strain RDEC-

GASTROENTEROLOGY Vol. 118, No.4

HI9A, an attaching/effacing rabbit pathogen expressing Stx-I which induces hemorrhagic colitis characterized by endothelial injury, edema and inflammation. After three days of infection, animals were treated with TMS or were untreated. Antibiotics were administered BID by NG gavage, in a protocol intended to model the anticipated use of antibiotics for an STEC infection just beginning to manifest clinical signs. Animals were observed for diarrhea. weight loss. and fecal shedding of RDEC-HI9A. then sacrificed on day seven post infection for determination of RDEC-HI9A colony counts and Stx levels in cecal contents by ELISA. Results: All animals lost weight over the three days following challenge. Untreated animals continued to lose weight, whereas those receiving TMS (p=.OO3) regained weight during therapy. Two deaths occured among the untreated, but none among the treated, animals. Diarrhea was more severe and of longer duration in the untreated group. Although there were no measurable differences in cecal RDEC-HI9A colony counts between the groups. Stx-I concentrations in cecal contents were reduced with TMS treatment. Sumary: Administration of TMS in an animal model of STEC infection reversed diarrhea and weight loss and reduced the amount of free Stx-I in the intestinal lumen. Conclusion: In this animal model of STEC infection, antibiotic administration for established infection appeared to have only benefical effects on the course, and the outcome, of the disease. Controlled clinical trials of antibiotic therapy for STEC infection may be warranted.

1761 PROTECTIVE EFFECTS OF HUMAN RECOMBINANT OSTEOGENIC PROTEIN-1 (BONE MORPHOGENIC PROTEIN-7) (BMP-7) IN CWSTRlDIUM DIFFICILE TOXIN A (TXA)-MEDIATED ENTERITIS AND TNBS-INDUCED COLITIS. Fabio Cataldi, Ignazio Castagliuolo, John T. LaMont, Andrew Keates, Charalabos Pothoulakis, Beth Israel Deaconess Med Ctr & Harvard Med School, Boston, MA. Bone morphogenic proteins (BMPs) are members of the transforming growth factor f3 superfamily involved in the formation of cartilage and bone. Recent evidence also indicates that administration of BMPs significantly reduce the severity of experimental renal and myocardial ischemia in rats. The current study was undertaken to examine the effects of BMP-7 and other BMPs in I) C. difficile TxA-mediated ileal fluid secretion and mucosal permeability, and 2) acute (5 days) and chronic (14 days) TNBSinduced colitis. Methods and Results: TxA (5 /Lg) or buffer were injected into ileal loops and intestinal responses were measured after 4 hr. Administration of BMP-7 (100 /Lg!kg, i.v) to Wistar rats 30 min prior to TxA administration inhibited TxA-induced ileal secretion by 38.9 % (p
1762 MURINE MODEL OF CAMPYLOBACTER INFECTION. Christopher H. Chang, Peggy A. Cotter. Jeff F. Miller, UCLA Sch of Medicine. Los Angeles, CA. Despite a strong association between Campylobacter and gastroenteritis, molecular mechanisms involved in its pathogenesis and host interactions remain poorly understood. Furthermore, a suitable animal model to study Campylobacterjejuni infection has not been well characterized. To investigate the molecular bases of Campylobacter pathogenesis and the host response to infection, we are developing experimental murine Campylobacter infection models. METHODS: Three strains of C3H mice were intragastrically inoculated with 109 cfu of Campylobacter jejuni strain 81-176: immunocompetent (wild type) mice with normal enteric flora, immunocompetent mice with an intestinal tract colonized only with a nonpathogenic Clostridial species (i.e. defined flora), and immunodeficient SCID mice with the same defined GI flora. RESULTS: Immunocompetent C3H mice (like BALB/c) with normal enteric flora became colonized inconsistently and at low levels; only 103 -5 cfu/gm and 103 -4 cfu/gm of viable C. jejuni were recovered from stool and large intestine tissue, respectively, at week I post-inoculation. By week 4, the wild type mice stopped excreting C. jejuni in stool and little or no C. jejuni was recovered from gut tissue. Immunocompetent mice with defined flora were more efficiently colonized. C. j~{uni was recovered from both stool and large intestine/cecum tissue at 10 cfu/gm I week after inoculation. However. by week 4 the yield of C. jejuni dropped to 106 - 7 cfu/gm of large intestine/