Evaluation of Clinician Interpretation and Prescribing Practices Based on Microbiologic Susceptibility Determination of "Susceptible-Dose Dependent”

Enterococcus spp. are among the leading causes of nosocomial infections with growing resistance to standard therapies like vancomycin. Daptomycin has activity against vancomycin resistant enterococci (VRE) infections. However, due to concerns over growing resistance, the Clinical Laboratory and Standards Institute re-evaluated the interpretative categories for daptomycin treatment of VRE in 2019 to include a new Susceptible-Dose Dependent ("SDD") category for E.faecium. The goal of this category was to direct clinicians to use higher dosing strategies, but its effectiveness has not yet been evaluated. We conducted a retrospective cohort study at the University of North Carolina Medical Center (UNCMC) from August 2016-July 2020 and included adult patients with VRE bacteremia with reported daptomycin susceptibility. Of 56 episodes of VRE bacteremia in which daptomycin was a clinically appropriate option, clinicians selected daptomycin in 81% of cases when interpreted as S and 71% of cases when SDD. Median dose prescribed was 10mg/kg for both interpretations. In a second analysis, we surveyed clinicians at UNCMC on their understanding of SDD, choice of therapy for bacteremia carrying S and SDD interpretations, and preferred resources for guidance. Of the 43 survey responses analyzed, 28 self-identified as physicians with 82% reporting either no previous encounter or no recollection of the SDD interpretation to describe daptomycin. There was no statistically significant difference between daptomycin selection in the case-based scenarios, but 82% physicians versus 21% pharmacists were unsure of a daptomycin dose when interpreted as SDD. Respondents were most like to consult local personnel over local guidelines to assist with optimal dosing. This work was presented to the Carolina Antimicrobial Stewardship Program at UNCMC to identify gaps in knowledge and ensure clinicians have access to resources to help guide treatment decisions.Doctor of Pharmac