[How to read new antimicrobial susceptibility testing results?]

Abstract

HOW TO READ NEW ANTIMICROBIAL SUSCEPTIBILITY TESTING RESULTS? Antimicrobial susceptibility testing (AST) results (formerly 'susceptible', 'intermediate' and 'resistant') are now expressed with the new susceptibility categories 'susceptible, standard dosing regimen', 'susceptible, increased exposure' and 'resistant'. These new categories introduce a paradigm shift in the way clinicians have to interpret AST results: uncertainties (previously embedded in the 'intermediate' category) now have to be dealt with exclusively by the laboratory, independently from the clinical categorization itself, and both 'susceptible, standard dosing regimen' and 'susceptible, increased exposure' categories are associated with a high likelihood of therapeutic success if appropriate dosing regimen is used. To help clinicians, a dosing table (fitting dosing regimens usually recommended in France, and consistent with clinical breakpoints) is now available as an appendix to the CA-SFM document (Comité de l'antibiogramme de la Société française de microbiologie), and can also be downloaded from the SPILF website (Société de pathologie infectieuse de langue française).