Vancomycin-resistant Enterococcus (VRE) screening swabs are performed widely as a means of identifying VRE carriers and prevention transmission. We tested whether these results could have unintended benefits in predicting the vancomycin susceptibility of subsequent infections with Enterococcus experienced by these patients.
A retrospective cohort study was conducted using an auto-populated antimicrobial stewardship database. Patients were included if 18 years of age or older, admitted to hospital between 2010 and 2015, and screened for VRE prior to developing an Enterococcus sterile-site infection. Test characteristics were derived using the screening swab result as test variable predicting the presence or absence of VRE in the sterile site Enterococcusspecies.
619 patients had sterile cultures positive for Enterococcus during the study period. Of these, 488/619 (79%) had previously undergone VRE screening. A total of 19/488 screening swabs were positive for VRE (4%), and a total of 10/488 sterile culture Enterococcal isolates were vancomycin resistant (2%). All VRE sterile isolates were E. faecium. The overall specificity of VRE swabs was 97% (92%-99%) and the overall sensitivity was 70% (35%-92%). The positive predictive value was 37% (17%-61%) and the negative predictive value was 99% (98%-100%). The positive likelihood ratio was 28 (14-56) and the negative likelihood ratio was 0.31 (0.12-0.80). A positive VRE screening swab yielded a post-test probability of 0.36 for VRE sterile site infection. In the United States, where the prevalence of VRE among enterococcus sterile isolates is as high as 0.15, a positive VRE screening swab would yield a post-test probability of 0.83 of vancomycin resistance (based on the derived likelihood ratio).
Prior VRE screening swab results are a useful tool for predicting vancomycin-resistance among sterile site Enterococcal infections. The results of this study suggest that those with a positive VRE screening swab, in whom enterococcus is being considered as a potential etiologic agent, should receive empiric treatment with linezolid or daptomycin until culture and sensitivity results are available; this may lead to earlier effective therapy, decreased average length of stay and reduced mortality.
D. Macfadden, None
N. Daneman, None