Expert Consensus on Polymyxin Antimicrobial Susceptibility Testing and Clinical Interpretation

Abstract

The polymyxins are important antimicrobial agents against antibiotic-resistant gram-negative bacilli. In 2020, the Clinical and Laboratory Standards Institute modified the clinical breakpoints for polymyxin susceptibility test by eliminating the “susceptible” interpretive category, only reporting intermediate (≤2 mg/L) and resistant (≥4 mg/L). However, the European Committee on Antimicrobial Susceptibility Testing recommended the use of clinical breakpoints of ≥2 mg/L as susceptible and >2 mg/L as resistant. The first-line laboratorians and clinicians in China have been perplexed by the inconsistence of international polymyxin clinical breakpoints and discouraged by the difficulty of conducting polymyxin susceptibility testing. Therefore, it is urgently needed to make it clear for the laboratorians in China to know how to accurately carry out polymyxin susceptibility testing and standardize the interpretation of susceptibility testing results. To this end, the experts from relevant fields were convened to formulate this consensus statement on the testing and clinical interpretation of polymyxin susceptibility. Relevant recommendations are proposed accordingly for laboratorians and clinicians to streamline their daily work.