"Improved Accuracy of Cefepime Susceptibility Testing for ESBL-producing Enterobacteriaceae using an On-Demand Digital Dispensing Method" published online yesterday in the Journal of Clinical Microbiology
Co-First Authors, KP Smith and Thea Brennan-Krohn, from the Kirby Research Laboratory and Susan Weir from the BIDMC Clinical Microbiology Laboratory collaboratively investigated the ability of commonly used clinical methods to support new "susceptible dose-dependent." MIC breakpoints newly introduced by the Clinical Laboratoryand Standards Institute for the antibiotic cefepime. The idea behind these SDD breakpoints was to offer clinicians the chance to treat otherwise poorly susceptible pathogens by increasing the cefepime dose in a manner tied to the isolate's MIC. To perform the study, we enriched for strains that should have borderline cefepime susceptibility based on a ceftriaxone resistant phenotype. Surprisingly, three commercial methods (Vitek 2, disk diffusion, and a manual microscan panel) performed poorly with only 40-60% categorical agreement with the broth microdilution reference standard. In contrast, the Digital Dispensing Method, (DDM) previously described by our laboratory was stastically equivalent to the reference method, and therefore was the only method capable of supporting susceptible dose dependent therapeutic rescue. The manuscript, "Improved Accuracy of Cefepime Susceptibility Testing for ESBL-producing Enterobacteriaceae using an On-Demand Digital Dispensing Method" can be found on the Journal of Clinical Microbiology website.