Suppression of the human mucosal-related colonic microflora with prophylactic parenteral and/or oral antibiotics.

The purpose of this investigation was to assess the effects of preoperative administration of parenteral antibiotics with or without concomitant preoperative administration of oral antibiotics on the colonic mucosal-related microflora. Thirty-one patients were studied in a prospective fashion. Group A patients (n = 8) had colonoscopic mucosal biopsies performed after mechanical bowel preparation. Group B patients (n = 5) received neomycin and erythromycin (NE), 1 g each following mechanical bowel preparation, at 1, 2, and 11 p.m. the evening prior to either elective colon resection (n = 2) or prior to colonoscopic biopsy (n = 3). Emergent trauma patients who had left colon or sigmoid perforations due to gunshot wounds requiring segmental resection comprised group C (n = 7). These patients received cefoxitin or cefotetan 2 g intravenously preoperatively. Individuals in group D (n = 11) all had elective left hemicolectomies or sigmoid resections due to nonobstructing malignancies. These patients underwent the same regimen as group B patients in addition to receiving intravenous cefoxitin perioperatively. Quantitative and qualitative bacterial cultures as well as scanning electron microscopy (SEM) were used to study the mucosa-associated flora. Tissue for culture and SEM were obtained from the pathologic specimen immediately after removal. The interval between the dosage of parenteral antibiotics to tissue removal was 3 hours in both groups. Anaerobic and aerobic counts were suppressed the greatest in patients receiving both oral and parenteral antibiotics (p = 0.0001). Mean anaerobic counts decreased from 3.4 X 10(7) in group A to 1.8 X 10(2) (mean cfu/g) in group D patients. Mean aerobic counts in group A decreased from 3.7 X 10(6) to 64 (mean cfu/g) in group D.(ABSTRACT TRUNCATED AT 250 WORDS)