Screening Strategy to Detect Vancomycin-Resistant Enterococci Conversion in Exposed Roommates
The Ontario Provincial Infectious Diseases Advisory Committee recommends screening VRE roommate contacts on different days, with one taken at minimum of 7 days post exposure (PE). This study aimed to better delineate the risk of conversion, by duration of exposure, and the optimal screening strategy after inadvertent exposure to VRE-positive roommates at a 430 bed community teaching hospital in Toronto, Canada.
All exposed roommates from 12/2004 to 3/2014 were screened for VRE at 3 time periods PE, as per protocol: T1 (0-1 day PE), T2 (2-4 days PE), and T3 (5-10 days PE) by rectal swab culture. Screens undertaken ≥11 days PE were grouped as T4. The sensitivity at various time periods for detecting newly colonized roommates were determined and defined as the number of patients who were culture positive at the specific time period(s) divided by the total number of VRE converted patients (from any follow-up period) who were swabbed at the specific time period(s).
Among 377 exposure episodes (367 patients), 253 (67%) had complete follow-up. VRE conversion was detected in 17 of the 253 episodes (7%). The sensitivity at each time period was: T1=58%, T2=63%, T3=75%, and T4=78%. Thirteen of the 17 VRE conversions (76%) were detected by 10 days (T3). Testing more than once, with at least one done at T3, achieved a higher sensitivity than testing at T1 alone (T1/T3 combined=100%, p=0.11 or T2/T3 combined=100%, p=0.24). Of those with first conversions at T4, none were screened more than once prior to T4 and the median time to positive test was 22 days. Contacts exposed to VRE patients for ≥3 days were significantly more likely to acquire VRE (11%) than those with <72 hours exposure (2.4%, p=0.01). Nonetheless, the conversion rate was significantly higher for those exposed <72 hours compared with the overall prevalence found on admission (2.4% vs. 0.17%, p<0.001). All patients were colonized; no infections developed in this cohort.
Roommates exposed to VRE patients are at substantial risk of becoming colonized, with the degree of risk increasing in those exposed for ≥3 days. Our data supports the provincial guidelines of screening exposed roommates at multiple times with at least one taken at 7 days PE.
Z. Pikula, None
M. Acomb, None
D. White, None
J. Tomassi, None
N. Muhammed, None
K. Katz, None