Reliability of Kirby-Bauer disk diffusion method for detecting carbapenem resistance in Acinetobacter baumannii-calcoaceticus complex isolates

摘要

We recently read an article on carbapenem susceptibility testing errors in studies that used three automated systems, disk diffusion (DD), Etest (ET), and broth microdilution (BMD), to investigate Acinetobacter baumannii-calcoaceticus complex (ABC) isolates. The authors concluded from the study that the manual methods are more accurate than automated 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. However, the pathogen is associated 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 carbapenem resistance are the recommended methods, but they are impractical to implement as routine tests in many clinical laboratories with a high isolate load that cannot afford automated susceptibility testing or the Etest. The Kirby-Bauer disk diffusion (KBDD) method is more economical and the standardized one used for testing susceptibility to most of the antibiotics. However, only a few studies have provided data on its reliability for testing carbapenems against ABC isolates.