Predominantly Antibiotic-resistant Intestinal Microbiome Persists in Patients With Pouchitis Who Respond to Antibiotic Therapy.

Background & Aims: Pouchitis that develops in patients with ulcerative colitis after total proctocolectomy and ileal pouch anal anastomosis is usually treated with antibiotics. Some patients have recurrence of flares, or become antibiotic-dependent, and require repeated courses or prolonged periods of antibiotic therapy. We investigated microbial factors associated with response to antibiotic treatment and development of antibiotic dependence in patients with pouchitis.

Methods: We performed a prospective study of 49 patients who had undergone pouch surgery at a tertiary center. Disease activity was determined based on clinical, endoscopic, and histologic criteria. Pouch phenotype was defined as recurrent-acute pouchitis (n = 6), chronic pouchitis and Crohn's-like disease of the pouch (n = 27), normal pouch from patient with ulcerative colitis (n = 10), and normal pouch from patient with familial adenomatous polyposis (n = 6). Fecal samples (n = 234) were collected over time during or in the absence of antibiotic treatment (ciprofloxacin and/or metronidazole). Thirty-three patients were treated with antibiotics, for a median of 425 days of cumulative antibiotic therapy, during follow-up. Calprotectin was measured and fecal DNA was sequenced using shotgun metagenomics and analyzed with specifically designed bioinformatic pipelines. Bacterial strains were isolated from fecal samples. We assessed their ciprofloxacin resistance and ability to induce secretion of inflammatory cytokines by HT-29 intestinal epithelial cells.

Results: Most antibiotic-treated patients (79%) had a clinical response to each course of antibiotics; however, 89% of those who completed a 4-week course relapsed within 3 months. Median calprotectin levels decreased by 40% in response to antibiotics. Antibiotic treatment reduced disease-associated bacteria such as Clostridium perfringens, Ruminococcus gnavus, and Klebsiella pneumoniae, but also beneficial species, such as Faecalibacterium prausnitzii. The microbiomes of antibiotic-responsive patients were dominated by facultative anaerobic genera (Escherichia, Enterococcus, and Streptococcus), with multiple ciprofloxacin-resistance mutations in drug target genes and confirmed drug resistance. However, these strains had lower potential for virulence and did not induce secretion of inflammatory cytokines by epithelial cells. After antibiotic cessation, patients had an abrupt shift in microbiome composition, with blooms of oral and disease-associated bacteria. In addition, antibiotic treatment enriched for strains that acquired multidrug resistance loci, encoding enzymes that confer resistance to nonrelated antibiotics, including extended-spectrum beta-lactamases.

Conclusions: The efficacy of antibiotic treatment of pouchitis might be attributed to the establishment of an antibiotic-resistant microbiome with low inflammatory potential. This microbiome might provide resistance against colonization by bacteria that promote inflammation. To avoid progression to antibiotic-dependent disease and its consequences, strategies such as short-term alternating antibiotics and nutrition- and microbiome-based interventions should be considered.