Effect of parenteral antibiotic administration on persistence of vancomycin-resistant Enterococcus faecium in the mouse gastrointestinal tract

A mouse model of vancomycin-resistant Enterococcus faecium (VRE) intestinal colonization was used to study the effect of different subcutaneous antibi otics on persistence and density of VRE colonization. Gastric inoculation o f a clinical VanB VRE isolate, in conjunction with oral vancomycin in drink ing water (250 mu g/mL), resulted in high-level VRE colonization (mean, 9.5 log(10) cfu/g) in all 169 experimental mice. After discontinuation of oral vancomycin, the level of VRE in the stool specimens of mice receiving subc utaneous saline steadily decreased (mean, 3.59 log(10) cfu/g at day 19). Su bcutaneous vancomycin, clindamycin, piperacillin-tazobactam, ticarcillin-cl avulanic acid, metronidazole, cefotetan, ampicillin, and ampicillin-sulbact am all promoted persistent high levels of stool VRE. Subcutaneous ceftriaxo ne, cefepime, ciprofloxacin, and aztreonam promoted increased VRE density t o a lesser degree or not at all. Thus, in a mouse model, vancomycin and ant ibiotics with potent antianaerobic activity promoted persistent high-densit y intestinal VRE colonization, whereas antibiotics lacking potent antianaer obic activity did not.