Colistin susceptibility testing of gram-negative bacilli: Better performance of vitek2 system than E-test compared to broth microdilution method as the gold standard test.

Introduction: Unavailability of optimal susceptibility testing (ST) challenges the clinical use of colistin. Broth microdilution (BMD), which is the reference for colistin ST, is inconvenient for diagnostics. Vitek2 and E-test although technically easier, are no longer recommended.