Expert Consensus on Polymyxin Antimicrobial Susceptibility Testing and Clinical Interpretation

Polymyxin was an important antimicrobial agent against resistant Gram-negative bacilli. In 2020, the American Clinical and Laboratory Standards Institute changed the clinical breakpoints of polymyxin, eliminating the "susceptible" interpretive category, and only reporting intermediate (I≤2 mg/L) and resistant(R≥4 mg/L) ones. However, the European Committee on Antimicrobial Susceptibility Testing recommended the use of susceptible (S≤2 mg/L), resistant (R > 2 mg/L) as the clinical breakpoints. The international disunity of clinical breakpoints of polymyxin brings great trouble to the domestic clinical staffs. Therefore, how to accurately carry out the susceptibility test of polymyxin and standardize the interpretation of its report is an urgent problem to be solved in the field of antibacterial drug application and anti-infection in China. To this end, we organized experts in related fields to normalize and interpret the susceptibility test of polymyxin and its results, and put forward corresponding suggestions of experts for reference.