Comparison of the Vitek 2, MicroScan, and Etest methods with the agar dilution method in assessing colistin susceptibility of bloodstream isolates of Acinetobacter species from a Korean university hospital

We evaluated three commercial colistin susceptibility testing methods using 213 bloodstream Acinetobacter isolates identified by gene sequencing. Compared to the agar dilution reference method, excellent categorical agreements (both 99.1%) were observed using Vitek 2 and Etest, compared to 87.3% (95.7% for Acinetobacter baumannii and 80.7% for non-baumannii Acinetobacter isolates) using MicroScan.