Effect of a single dose of cefotaxime or ceftriaxone on human faecal flora. A double-blind study

The effect of cefotaxime and ceftriaxone on faecal flora was investigated in women undergoing routine vaginal or abdominal hysterectomy. Three groups of 9 patients received, in a double-blind fashion and just before surgery, cefotaxime 2g intravenously, ceftriaxone 2g intravenously or no antibiotic (controls). Stools were collected before prophylaxis (sample 1) and after surgery (samples 2 and 3). The only alteration after cefotaxime was a decrease of non-fastidious aerobic Gram-negative flora in sample 2. The same effect was more pronounced after ceftriaxone (p less than 0.01) which, in addition, increased yeast colonies (p less than 0.05) in sample 2. In sample 3, more resistant (MIC greater than 32 mg/L) aerobic and anaerobic bacteria were found after ceftriaxone (log10 median 7.5 and 9.0, respectively) than after cefotaxime (4.2 and 6.0) or in controls (4.4 and 6.6) [p less than 0.01 in each case]. Group D streptococci and Gram-positive cocci remained unchanged in the 3 groups. Clostridium difficile cytotoxin assays were negative. The effects on faecal flora were more pronounced after ceftriaxone.