Laboratory-Based Surveillance for Vancomycin-Resistant Enterococci: Utility of Screening Stool Specimens Submitted for Clostridium difficile Toxin Assay

Abstract

Objective:: To study vancomycin-resistant enterococci (VRE) gastrointestinal colonization prevalence in high-risk hospitalized patients and to assess the cost and utility of this laboratory-based surveillance.Setting:: Large university teaching hospital.Design:: Quarterly prevalence culture survey of 50 stool specimens submitted forClostridium difficiletoxin A assay from October 1996 through June 1999 (n=526). Screening culture survey of allC difficile-positive stool specimens from July 1998 through June 1999 (n=140).Patients:: Specimens for analysis were collected from patients who were admitted to the hospital and who hadC difficiletoxin A testing ordered. Patient samples were excluded from analysis if they were obtained from patients not hospitalized at UCLA Medical Center, if theC difficiletoxin assay result was indeterminate, or if the patient was known to have previous VRE colonization or infection.Results:: During quarterly surveillance, VRE was detected in 19.8%,C difficiletoxin A in 9.5%, and both VRE andC difficiletoxin A in 3.2% of stool specimens submitted forC difficiletoxin assay. Patients whose stool specimens were positive forC difficiletoxin A were significantly more likely than those whose specimens were negative to have VRE detected (odds ratio, 2.3; 95% confidence interval, 1.2-4.5). Based on these findings, in July 1998, we began routine screening of allC difficile-positive stool specimens for VRE. From July 1998 through June 1999, 58 (41.4%) of 140 patients withC difficile-positive specimens had VRE newly detected in the stool. The combined cost of the two laboratory-based surveillance strategies was approximately $62 per VRE-positive patient identified and $5,800 per year.Conclusion:: Quarterly surveillance of stool submitted forC difficileassay combined with screening allC difficile-positive stools is a cost-effective and efficient strategy for detecting VRE stool colonization among high-risk hospitalized patients. Such a laboratory-based surveillance should be included as part of a comprehensive program to limit nosocomial VRE transmission.