Intestinal Enterococcus faecium Colonization Improves Host Defense during Polymicrobial

(See the editorial commentary by Bertics and Wiepz on pages 679–81) Background. Vancomycin-resistant (VR) Enterococcus faecium is increasingly found to colonize and infect hospitalized patients. Enterococci are frequently isolated from polymicrobial infections originating from the in-testines. The impact of VR E. faecium on these infections and vice versa is not clear. Methods. Mice were intestinally colonized with VR E. faecium during oral vancomycin treatment; control mice received oral vancomycin only. Fourteen days later, cecal ligation and puncture (CLP) was performed in all mice to induce polymicrobial peritonitis in the presence or absence of VR E. faecium colonization. Results. VR E. faecium colonization per se was not associated with systemic dissemination of VR E. faecium. CLP resulted in systemic VR E. faecium infection in all VR E. faecium–colonized mice, with high VR E. faecium loads in peritoneal lavage fluid, blood, liver, and lungs. Forty-eight hours after CLP, mice infected with VR E. faecium had significantly lower bacterial loads in all organs tested than mice not infected with VR E. faecium. Additionally, lower inflammatory parameters were measured in VR E. faecium–infected mice. CLP induced transient liver and kidney damage, with a faster recovery in VR E. faecium–colonized mice. Conclusions. VR E. faecium infection, originating from a natural source (the intestinal tract), does not worsen the outcome of CLP-induced polymicrobial peritonitis and sepsis but rather facilitates bacterial clearance an