EFFECT OF VANCOMYCIN ON INTESTINAL FLORA OF PATIENTS WHO PREVIOUSLY RECEIVED ANTIMICROBIAL THERAPY

To evaluate the ecological disturbances of peroral vancomycin administ ration following cephalosporin administration, 20 healthy volunteers r eceived cefuroxime axetil tablets (250 mg) perorally twice a day for 1 week, and 10 of these volunteers subsequently received vancomycin cap sules (125 mg) perorally four times daily for 7 days, The concentratio n of vancomycin in feces after 1 week of vancomycin administration was high (mean +/- SD, 520 +/- 197 mg/kg), which correlated with the ecol ogical disturbances noted in the vancomycin recipients, Vancomycin adm inistration resulted in a rapid decrease in the numbers of intestinal Enterococcus faecium, Enterococcus faecalis, and Enterococcus durans ( P less than or equal to .05), while there was a significant emergence of motile enterococci with decreased susceptibility to vancomycin (Ent erococcus gallinarum and Enterococcus casseliflavus; minimum inhibitor y concentration, 4-16 mg/L) (P less than or equal to .01). Because of vancomycin administration, there was also a significant overgrowth of vancomycin-resistant Pediococcus species and lactobacilli as well as o f Klebsiella species, Citrobacter species, and Enterobacter species (P less than or equal to .01), The numbers of bifidobacteria and Bactero ides species were significantly reduced during vancomycin administrati on. None of the enterococcal strains carried vanA or vanB, Twenty-two of the 27 motile enterococci carried the vanC-1 gene specific for E. g allinarum, whereas five strains carried the vanC-2(C-3)gene, thus impl icating that they were E. casseliflavus or Enterococcus flavescens.