In order to maintain the mucosal barrier against luminal microorganisms the intestinal epithelial cells synthesise various broad-spectrum antimicrobial peptides including defensins and cathelicidins.
Recent studies indicate that both may be deficient in Crohn's disease.
Dr Sabine Nuding and colleagues from Germany elucidated the possible functional consequences of this deficiency antimicrobial activity.
The research team investigated colonic mucosa from patients with inflammatory bowel disease (IBD) and healthy controls.
The team established a flow cytometric assay to quantitate bacterial killing and tested the antibacterial activity of cationic peptide extracts from colonic biopsies.
The biopsies were taken from 22 patients with active or inactive ileocolonic or colonic Crohn's disease, 29 ulcerative colitis and 13 controls.
|Antimicrobial effect against E. coli was lower in Crohn's|
The team compared these against clinical isolates of Bacteroides vulgatus and Enterococcus faecal is.
Reference strains included Escherichia coli American Type Culture Collection 25922 and Staphylococcus aureus American Type Culture Collection 25923.
The researchers found that, compared with controls and ulcerative colitis there was a reduced antimicrobial effect in Crohn's disease extracts that was most evident against B. vulgatus.
The team found that the antimicrobial effect against E. coli and E. fecalis was lower in Crohn's disease compared with ulcerative colitis.
Activity against S. aureus disclosed a similar pattern, but was less pronounced.
The research team observed that the differences were independent of the inflammation status or concurrent steroid treatment.
The team noted that bacteria incubated with biopsy extracts from ulcerative colitis patients frequently showed a characteristic change in cell size and granularity.
Bacteria incubated with biopsy extracts from ulcerative colitis patients were more frequently compatible with more extensive membrane disintegration.
Dr Nuding's team concluded, "Crohn's disease of the colon is characterized by a diminished functional antimicrobial activity that is consistent with the reported low antibacterial peptide expression."