Mucosal bacterial microflora and mucus layer thickness in adolescents with inflammatory bowel disease.

Aim: To assess the mucosa-associated bacterial microflora and mucus layer in adolescents with inflammatory bowel disease (IBD).

Methods: Sixty-one adolescents (mean age 15 years, SD+/-4.13) were included in the study. Intestinal biopsies from inflamed and non-inflamed mucosa of IBD patients and from controls with functional abdominal pain were cultured under aerobic and anaerobic conditions. The number of microbes belonging to the same group was calculated per weight of collected tissue. The mucus thickness in frozen samples was measured under a fluorescent microscope.

Results: The ratios of different bacterial groups in inflamed and non-inflamed mucosa of IBD patients and controls were specific for particular diseases. Streptococcus spp. were predominant in the inflamed mucosa of Crohn's disease (CD) patients (80% of all bacteria), and Lactobacillus spp. were predominant in ulcerative colitis patients (90%). The differences were statistically significant (P=0.01-0.001). Lower number of bifidobacteria was observed in the whole IBD group. A relation was also found between clinical and endoscopic severity and decreased numbers of Lactobacillus and, to a lesser extent, of Streptococcus in biopsies from CD patients. The mucus layer in the inflamed sites was significantly thinner as compared to controls (P=0.0033) and to non-inflamed areas in IBD patients (P=0.031).

Conclusion: The significantly thinner mucosa of IBD patients showed a predominance of some aerobes specific for particular diseases, their numbers decreased in relation to higher clinical and endoscopic activity of the disease.