Bacterial Biofilm Suppression with Antibiotics for Ulcerative and Indeterminate Colitis: Consequences of Aggressive Treatment

Abstract

Antibiotics are commonly used in inflammatory bowel disease (IBD). Little is known about their effect on the mucosal flora. The mucosal flora was investigated in colonoscopic biopsies from six groups of 20 IBD patients each. Patients were selected with regard to duration of/interval to combined metronidazole and ciprofloxacin therapy: group I patients with 1 day and group II with 7-14 days of antibiotic therapy, group III-V patients evaluated 1-4 weeks, 2-18 weeks, 26-36 weeks after cessation of antibiotic therapy, respectively. The control group VI included patients without antibiotic therapy. Thirty different fluorescent in situ hybridization (FISH) probes representative of the diversity of the human intestinal flora were applied to all specimens. Bacteria adherent to mucosa could be seen exclusively in DAPI stain and were practically nonamenable to FISH probes in patients on antibiotics (0.001-3+/-0.001-5)x10(10)/mL. Occurrence and concentrations were significantly reduced in groups I and II as compared to untreated controls. The mucosal bacteria were significantly augmented after cessation of antibiotic therapy in group III (13.2+/-4.3) and group IV (5.8+/-2) but not in group V (1.1+/-0.8) as compared to group VI (0.5+/-0.4)x10(10)/mL. Neither Bacteroides nor Enterobacteriaceae groups were permanently suppressed by metronidazole-ciprofloxacin therapy. The suppressing effects of antibiotics on the mucosal flora are accompanied by massive rebound effects. The concentrations of mucosal bacteria are dramatically increased as soon as 1 week after cessation of antibiotic therapy, remaining at a level that is at least one power higher over a period of 5 months as compared to the group without antibiotic treatment.