Coexistence of vancomycin-resistant enterococci and Staphylococcus aureus in the intestinal tracts of hospitalized patients

The potential for transfer of vancomycin-resistance genes from enterococci to Staphylococcus aureus exists when these organisms share an ecologic niche. We performed an 8-month prospective study to determine the frequency at which S. aureus and vancomycin-resistant enterococci (VRE) coexist in the intestinal tracts of VRE-colonized patients and evaluated whether antianaerobic antibiotic therapy promoted increased density of S. aureus colonization. Of 37 patients colonized with vancomycin-resistant Enterococcus faecium, 23 (62%) had S. aureus recovered from stool specimens and 20 (87%) had methicillin-resistant strains. There was no significant difference in the mean density ( +/- standard deviation) of S. aureus during versus greater than or equal to1 month after discontinuation of antianaerobic antibiotic therapy (5.1 +/- 1.5 vs. 4.7 +/- 1.6 log(10) colony-forming units per gram of stool; P = .34). No S. aureus isolates were resistant to vancomycin. S. aureus and VRE often coexist in the intestinal tract, providing a potential reservoir for the emergence of vancomycin-resistant S. aureus isolates.