Reliability of Kirby-Bauer Disk Diffusion Method for Detecting Carbapenem Resistance in Acinetobacter baumannii-calcoaceticus Complex Isolates

We recently read an article on carbapenem susceptibilitytesting errors in studies that used three automated sys-tems, disk diffusion (DD), Etest (ET), and broth microdilution (BMD), to investigate Acinetobacter baumannii-calcoaceticus complex (ABC) isolates (1). The authors concluded from the study that the manual methods are more accurate than auto-mated methods. The error rates for testing susceptibility to imipenem and meropenem by DD and the Etest were found to be within an acceptable range compared with MIC detected by BMD. Carbapenems are widely used against multidrug-resis-tant (MDR) ABC isolates (2). However, the pathogen is asso-ciated with increasing carbapenem resistance, which limits therapeutic options and challenges effective hospital infection control. Thus, as antimicrobial resistance increases, accurate susceptibility testing to guide therapeutic options is essential. Agar microdilution and broth microdilution for detecting car-