Perianal fistulas in Crohn's disease are predominantly colonized by skin flora: implications for antibiotic treatment?

In this study we aimed to determine the microorganisms found in perianal fistulas in Crohn's disease and whether treatment with ciprofloxacin affects these microorganisms. Thirteen patients (males/females, 7/6; median age, 34 years; range, 18-61 years) with fistulas were treated with infliximab, 5 mg/kg intravenously, at weeks 6, 8, and 12 and randomized to double-blind treatment with ciprofloxacin, 500 mg bd (n = 6), or placebo (n = 7) for 12 weeks. Samples were taken at baseline and at weeks 6 and 18. In the ciprofloxacin group 10 different genera of microorganisms were identified, while 13 genera could be identified in the placebo group. Gram-negative enteric floras were present in a small minority. The genera found in patients with perianal fistulas were predominantly gram-positive microorganisms. Therefore, antimicrobial treatment should be directed toward these microorganisms.