Inhibition of Vancomycin-Resistant Enterococci by an In Vitro Continuous-Flow Competitive Exclusion Culture Containing Human Stool Flora

7cfu/mL of VRE, the density of VRE was reduced but not eliminated. These data support the hypothesis that the indigenous intestinal flora inhibit growth of VRE and suggest that CFCE cultures may be a useful means to study interactions between the indigenous flora and VRE. The intestinal tract is an important source for the spread of vancomycin-resistant enterococci (VRE), and fecal colonization may persist for months in many patients [1]. In mice [2] and in colonized patients [1], we demonstrated that antibiotics with activity against anaerobes promote intestinal overgrowth of VRE, whereas antibiotics with minimal antianaerobic activity do not. We also demonstrated that patients with high-density colonization are more likely to contaminate the environment than are those with low-density colonization [1]. These findings suggest that strategies designed to maintain or restore the competing anaerobic intestinal flora might be effective in limiting the spread of VRE. The in vitro anaerobic continuous-flow culture model developed by Freter et al. [3] was shown to closely reproduce a variety of bacterial interactions that occur in the intestinal tracts of mice. This technique has been used to develop continuous-flow competitive exclusion (CFCE) cultures derived from cecal contents of adult chickens that prevent colonization with enteric pathogens in newly hatched chicks [4]. We hypothesized that a CFCE culture of human stool microflora would inhibit VRE colonization. Our objective was to develop such a culture and to test its ability to inhibit VRE in vitro.