Discrepancies in susceptibility testing to colistin in Acinetobacter baumannii: The influence of slow growth and heteroresistance

•The increasing use of colistin has led to an increase in Acinetobacter baumannii resistance.•This situation has shown limitations of colistin for in vitro susceptibility testing.•The impact of colistin-resistance mechanisms in susceptibility methods was evaluated.•Most of the errors were found in isolates with MIC values close to the breakpoint.•The rapid colistin colorimetric Acinetobacter method showed the best performance.