Laboratory-based surveillance for vancomycin-resistant enterococci: Utility of screening stool specimens submitted for Clostridium difficile toxin assay

OBJECTIVE: To study vancomycin-resistant enterococci (VRE) gastrointestinal colonization prevalence in high-risk hospitalized patients and to assess t he cost and utility of this laboratory-based surveillance. SETTING: Large university teaching hospital. DESIGN: Quarterly prevalence culture survey of 50 stool specimens submitted for Clostridium difficile toxin A assay from October 1996 through June 199 9 (n = 526). Screening culture survey of all C difficile-positive stool spe cimens from July 1998 through June 1999 (n = 140). PATIENTS: Specimens for analysis were collected from patients who were admi tted to the hospital and who had C difficile toxin A testing ordered. Patie nt samples were excluded from analysis if they were obtained from patients not hospitalized at UCLA Medical Center, if the C difficile toxin assay res ult was indeterminate, or if the patient was known to have previous VRE col onization or infection. RESULTS: During quarterly surveillance, VRE was detected in 19.8%, C diffic ile toxin A in 9.5%, and both VRE and C difficile toxin A in 3.2% of stool specimens submitted for C difficile toxin assay. Patients whose stool speci mens were positive for C difficile toxin A were significantly more likely t han 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 199 8, we began routine screening of all C difficile-positive stool specimens f or VRE. From July 1998 through June 1999, 58 (41.4%) of 140 patients with C difficile-positive specimens had VRE newly detected in the stool. The comb ined cost of the two laboratory-based surveillance strategies was approxima tely $62 per VRE-positive patient identified and $5,800 per year. CONCLUSION: Quarterly surveillance of stool submitted for C difficile assay combined with screening all C difficile-positive stools is a cost-effectiv e and efficient strategy for detecting VRE stool colonization among high-ri sk hospitalized patients. Such a laboratory-based surveillance should be in cluded as part of a comprehensive program to limit nosocomial VRE transmiss ion.