Changes in the intestinal flora after the administration of prophylactic antibiotics to patients undergoing a gastrectomy.

ABSTRACT

PURPOSE: Changes in the intestinal flora were investigated in patients administered antibiotics for 4 days after a gastrectomy. METHODS: Twenty-four patients were divided into each of the following groups cefazolin, 1 g every 8 h; cefozopran, 0.5 g every 8 h; flomoxef, 1 g every 8 h. All drugs were administered intravenously for a 4-day period. RESULTS: Antibiotic prophylaxis caused no major change in the total number of anaerobes because of the preservation of the Bacteroides fragilis group. However, the number of Bifidobacterium, Lactobacillus, Eubacterium, and Veillonella spp. decreased by an average of 100-fold. These changes were accompanied by an overgrowth of Enterococcus spp. and Pseudomonas aeruginosa. CONCLUSIONS: Four days of antibiotic prophylaxis after surgery caused a suppression of colonization resistance in the intestinal flora. Certain genera of anaerobes may thus play an important role in preventing overgrowth of antibiotic-resistant organisms after surgery. Surgeons should decide the duration of antibiotic use after carefully considering its influence on the intestinal flora.