Direct disk diffusion susceptibility testing from respiratory tract specimens: focus on Pseudomonas aeruginosa

Abstract

The aim of this study was to evaluate the application of direct disk diffusion (DDD) testing to respiratory tract specimens for the prediction of the antimicrobial susceptibility profile. DDD was performed on 144 specimens containing P. aeruginosa and the disk diffusion test was used as reference method. Agreement with the reference method was 77.8% for amikacin, 69.4% for cefepime, 86.1% for levofloxacin, 87.5% for meropenem, and 62.5% for piperacillin/tazobactam. Very major errors were observed for all agents, except levofloxacin. Our study showed that DDD results are inaccurate and may lead to errors in early decision-making regarding antibiotic therapy for lower respiratory tract infections.

Keywords

• Pseudomonas aeruginosa
• Direct susceptibility testing
• Ventilator-associated pneumonia
• Disk diffusion