Abstract
Recent efforts have employed antimicrobial susceptibility assays to describe the residual antimicrobial activity of antibiotics and their transformation products in a variety of environmental processes. Some authors have evaluated the results of these assays using the minimum inhibitory concentration (MIC); however, this approach has fundamental weaknesses. To highlight best practices, this comment describes the advantages of using dose-response curves to calculate the half maximal inhibitory concentration (IC50) and the potential impacts of growth media on the antimicrobial activity of sulfonamide antibiotics. •Disadvantages of MIC-based analysis of residual antimicrobial activity.•Comparison of IC50 values is best practice for antimicrobial activity measurement.•Growth media may interfere with antimicrobial activity of sulfonamides.