A comparative study of Escherichia coli strains isolated from the intestinal mucosa of Crohn's disease patients and healthy subjects

Abstract number: p536

Martinez-Medina  M., Aldeguer  X., Gonzalez-Huix  F., Acero  D., Garcia-Gil  L.J.

Objectives: 

To analyse and compare the E. coli strains present in CD patients with those from healthy controls.

To identify and characterise the pathogenic strains.

Methods: 

We have used fresh biopsies which have been subjected to a mild sonication in order to discard the transient and loosely attached bacteria followed by a mild osmotic shock to release any intracellular bacteria from those outer epithelium cells. The isolation procedure consisted of the incubation of samples in TBX agar medium at 44.5°C o/n. Colonies were kept for a first confirmation screening of E. coli by the indole assay. Typing of isolates was performed by REP-PCR, using a primer set targeting the IS3 as described previously [1]. Clonality was further checked by PFGE.

Results: 

A total of 1600 presumptive E. coli from 8 CD patients, 10 healthy controls and 2 patients suffering from Ulcerative Colitis, were isolated. Several subtypes of E. coli were found in all specimens. Each screened person carried a unique set of E. coli subtypes that was different from the others. Some E. coli isolated from the transient microbiota were different from the attached counterparts. In addition, after application of osmotic shock, additional types were found in most of samples. Although the study of more samples is underway, preliminary results suggest that CD patients harbour a higher subtype numbers than healthy subjects.

Conclusion: 

The number and diversity of E coli attached to the intestinal mucosa of CD patients is congruent with some recent hypothesis on the implication of this bacterium in the pathogenesis of Crohn's disease [2–5].

Reference

[1] Thompson et al, 1998. Journal of Clinical Microbiology: 36(5): 1180–84

[2] Darfeuille-Michaud A et al, 2004. Gastroenterology; 127(2): 412–21

[3] Helen M. Martin et al, 2004. Gastroenterology;127(1): 80–93

[4] Masseret E et al, 2001. Gut:48:320–325

[5] Ryan M.D et al, 2004. Am J Gastroenterol: 99:1539–1543