Influence of cephalosporines III generation with varying biliary excretion on fecal flora and emergence of resistant bacteria during and after cessation of therapy.

Excretion of an antibiotic bile may result in high intraintestinal concentrations and thus alteration in the fecal flora. We investigated the effect of ceftriaxone (45% biliary excretion) and cefotaxime (less than 5% biliary excretion) on the aerobic fecal flora. Ceftriaxone eradicated susceptible enteric organisms and resulted in overgrowth of Candida spp. and resistant enterococci. In some patients multiresistant gram negative bacteria appeared during of after therapy. Cefotaxime had a moderate effect on fecal microecology and did not promote the emergence of resistant organisms.