A comparison of disk diffusion method and E-test in determining the susceptibility and resistance of Klebsiella and Acinetobacter strains to cefepime in patients with ventilator-associated pneumonia admitted to the intensive care unit

Abstract

Introduction: Ventilator-associated pneumonia (VAP) which is mostly caused by microorganisms such as Acinetobacter and Klebsiella is one of the causes of death among patients in the intensive care unit (ICU). Objectives: The aim of this study was to compare disk diffusion method and E-test in detecting the susceptibility of Klebsiella and Acinetobacter strains isolated from lung secretions of patients with VAP admitted to the ICU treated with cefepime. Patients and Methods: In this cross-sectional descriptive study, 100 patients with VAP including 55 and 45 cases infected with Acinetobacter and Klebsiella, respectively, according to the antibiogram participated. The susceptibility and resistance of Acinetobacter and Klebsiella strains to cefepime was determined using disk diffusion method and E-test. In addition, kappa test was used to determine the sensitivity and specificity of disk diffusion method compared to E-test. Results: The sensitivity and specificity of the disk diffusion method were 100% and 25%, respectively and its positive predictive value was 87.5% and its negative predictive value was 100%. The kappa coefficient was 0.35 (P<0.0001), which indicates a significant agreement between the two tests. Conclusion: Disk diffusion method has high sensitivity and low specificity in comparison to E-test in determining the resistance and susceptibility of Acinetobacter and Klebsiella strains to cefepime in patients with VAP admitted to the ICU.