A continuous-flow competitive exclusion (CFCE) culture model of human stool microflora was used to examine whether supplemental anaerobic gas is necessary for maintenance of anaerobes and inhibition of vancomycin-resistant Enterococcus (VRE). CFCE cultures of human stool microflora were maintained with supplemental nitrogen, without supplemental nitrogen, or with percolated room air. Cultures with or without supplemental nitrogen maintained >9 log(10) CFU mL(-1) of obligate anaerobes and eliminated 10(6) CFU mL(-1) of VRE. When room air was percolated into the culture, anaerobes were detected at less than or equal to2 log(10) CFU mL(-1), and the same VRE inoculum was not eliminated (P < 0.001). These data demonstrate that human stool CFCE cultures maintain high levels of obligate anaerobes and inhibit VRE without the addition of supplemental anaerobic gas.