Effect of E. coli Nissle 1917 on post-inflammatory visceral sensory function in a rat model T. LIEBREGTS,* B. ADAM,* A. BERTEL,  S. JONES,* J. SCHULZE, à C. ENDERS, à U. SONNENBORN, à K. LACKNER§ & G. HOLTMANN* *Department of Gastroenterology, Hepatology and General Medicine, University of Adelaide, Royal Adelaide Hospital, South Australia, Adelaide, Australia  Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Essen, Essen, Germany àArdeypharm GmbH, Herdecke, Germany §Institute of Pathology, University of Graz, Graz, Austria Abstract Objective: Visceral hyperalgesia (VH) plays a key role for the manifestation of functional gastro- intestinal (GI) disorders. In a subgroup of patients, the initial manifestation is preceded by GI inflammation. Recent studies have demonstrated an improvement of inflammation and symptoms during treatment with Escherichia coli Nissle 1917 (EcN). Aim: We aimed to characterize the effects of EcN on visceral sensitivity in a rat model of post-inflamma- tory VH. Methods: Male Lewis rats underwent colorectal instillation of trinitrobenzenesulphonic acid (TNBS) plus an equal amount of ethanol (test group) or phy- siological saline solution (control group). After 28, 35 and 42 days, standardized colorectal distensions were performed and the visceromotor reflex (VMR) of abdominal wall muscles was quantified by elec- tromyographic recording. From day 28 onwards, EcN was administered in drinking water. Results: After TNBS, a significant increase of VMR was observed compared with saline controls over all study days. Administration of EcN reduced the TNBS- induced hyperalgesia [EcN: 863 ± 125 lV vs placebo: 1258 ± 157 lV (P < 0.05)] at day 35, while there were no significant alterations at any other study day. Conclusion: The EcN administration caused a signi- ficant reduction of VH. Whether EcN might play a role in the treatment of post-infectious functional bowel disorders remains to be investigated in further studies. Keywords post-inflammatory, E. coli Nissle, visceral hyperalgesia. INTRODUCTION Chronic abdominal pain or discomfort is a key finding in patients with functional gastrointestinal (GI) disor- ders. These patients show lowered perceptual and pain thresholds to visceral stimuli. 1 Acute GI infections are known to play an important role with regard to the initiation of symptoms. 2,3 These symptoms persist although the infection is cured, leading to the concept of post-infectious functional bowel disorders. Interestingly, a transient colitis in rats results in a long-lasting visceral hyperalgesia (VH). 4 Escherichia coli Nissle 1917 (EcN) is a non-pathogenic representative of the human intestinal flora. 5 The strain possesses none of the virulence properties typical of intestinal and extraintestinal pathogenic E. coli vari- ants. 6 The EcN shows competitive characteristics against other microorganisms, especially pathogenic ones. 7 Probiotics have been reported to be efficient in treatment of inflammatory bowel disease. 8 Although very little is known about efficiency of probiotics in the treatment of functional GI disorders, and clinical observations for treatment of irritable bowel syndrome (IBS) with probiotics are still controversial. 9–12 Symp- toms in post-inflammatory IBS are most likely linked to VH. Thus, we aimed to characterize the effects of treatment with probiotic E. coli Nissle 1917 in an animal model of post-inflammatory VH. Address for correspondence Gerald Holtmann MD, Professor of Medicine, Department of Gastroenterology, Hepatology and General Medicine, University of Adelaide, Royal Adelaide Hospital, Adelaide, SA 5000, Australia. Tel: +61 8 8222 2412; fax: +61 8 8222 2414; e-mail: gerald.holtmann@adelaide.edu.au Received: 19 October 2004 Accepted for publication: 1 December 2004 Neurogastroenterol Motil (2005) 17, 410–414 doi: 10.1111/j.1365-2982.2005.00638.x 410 Ó 2005 Blackwell Publishing Ltd