Co-carriage rates of vancomycin-resistant Enterococcus and extended-spectrum beta-lactamase-producing bacteria among a cohort of intensive care unit patients: Implications for an active surveillance program

OBJECTIVE: To assess the co-colonization rates of extended-spectrum beta-lactamase (ESBL)-producing bacteria and vancomycin-resistant Enterococcus (VRE) obtained on active surveillance cultures. DESIGN: Prospective cohort study. SETTING: Medical and surgical intensive care units (ICUs) of a tertiary-care hospital. PATIENTS: Patients admitted between September 2001 and November 2002 to the medical and surgical ICUs at the University of Maryland Medical System had active surveillance perirectal cultures performed. Samples were concurrently processed for VRE and ESBL-producing bacteria. RESULTS: Of 1,362 patients who had active surveillance cultures on admission, 136 (10%) were colonized with VRE. Among these, 15 (positive predictive value, 11%) were co-colonized with ESBL. Among the 1,226 who were VRE negative, 1,209 were also ESBL negative (negative predictive value, 99%). Among the 1,362 who had active surveillance cultures on admission, 32 (2%) were colonized with ESBL. Among these, 15 (47%) were co-colonized with VRE. Of the 32 patients colonized with ESBL, 10 (31%) had positive clinical cultures for ESBL on the same hospital admission. For these 10 patients, the surveillance cultures were positive an average of 2.7 days earlier than the clinical cultures. CONCLUSIONS: Patients who are colonized with VRE can also be co-colonized with other antibiotic-resistant bacteria such as ESBL-producing bacteria. Our study is the first to measure co-colonization rates of VRE and ESBL-producing bacteria. Isolating VRE-colonized patients would isolate 47% of the ESBL-colonized patients without the need for further testing. Hence, active surveillance for VRE should also theoretically diminish the amount of patient-to-patient transmission of ESBL-producing bacteria.