Modulation of the intestinal flora of mice by parenteral treatment with broad-spectrum cephalosporins.

A study was performed to determine the effect of parenteral treatment with four broad-spectrum cephalosporins (cefoperazone, ceftriaxone, ceftazidime, and cefepime) on the number of aerobic gram-negative rods and on the outgrowth of Candida albicans and a multiresistant strain of Citrobacter freundii in the feces of mice. The estimated fractions of a parenteral dose that were excreted into the gastrointestinal tract were 0.37 for cefoperazone, 0.11 for ceftriaxone, 0.03 for ceftazidime, and 0.002 for cefepime. All four cephalosporins significantly decreased the number of aerobic gram-negative rods in the feces, and virtually all gram-negative rods were eliminated at high doses of cefoperazone, ceftazidime, and ceftriaxone. Furthermore, at high doses these three compounds led to a significant increase of the outgrowth of resistant Citrobacter freundii. The outgrowth of Candida albicans was increased at high doses of cefoperazone and ceftriaxone, whereas ceftazidime and cefepime did not have this effect. The most profound changes in the gastrointestinal ecology were observed during treatment with high doses of cefoperazone. The results suggest that the colonization resistance of the gastrointestinal tract can be substantially decreased by parenteral treatment with cefoperazone and, to a lesser extent, with ceftriaxone and ceftazidime.