Clinical and epidemiological significance of enterococci intrinsically resistant to vancomycin (possessing the vanC genotype)

摘要

Constitutive low-level vancomycin resistance is found intrinsically in certain enterococcal species and is encoded by vanC ligase genes. These intrinsically vancomycin-resistant enterococci (VRE) will be referred to as VANC VRE. A prospective study to determine the clinical and epidemiologic significance of VANC VRE was conducted. VANC VRE were recovered from the stools of 34 of 601 (5.7%) patients, a rate similar to that obtained for the stools of 100 outpatients in the community (5%). VANC VRE were also isolated from the nonstool specimens of 9 of 538 patients (1.7%), including two patients with bacteremia. No VRE of the vanA or vanB genotypes were detected in nonstool specimens. Eighty-two hospital contacts of the first 23 patients found to be colonized or infected with VANC VRE were screened, and 6 contacts were found to be gastrointestinal carriers of VANC VRE. However, typing of isolates from these 6 contacts by pulsed-field gel electrophoresis with SmaI showed the isolates to be unique and different from those recovered from the index patients. In fact, all VANC VRE isolates from different patients in this study were unique. A case-control study with patients who were negative when screened for VANC VRE as controls failed to identify any risk factor associated with colonization or infection with this organism. VANC VRE were infrequently recovered from clinical specimens but were occasionally found as part of the normal stool flora. Since no transmission between patients was documented, additional isolation procedures may not be necessary for patients colonized or infected with VANC VRE.