title: Comparison of direct antimicrobial susceptibility testing methods for rapid analysis of bronchial secretion samples in ventilator-associated pneumonia.
abstract: Two hundred and fifty tracheal aspirates were subjected to direct antimicrobial susceptibility testing by disk diffusion, Etest and inoculation on antibiotic-enriched MacConkey agar plates. Results were compared with those obtained using an automated system on microorganisms recovered from standard quantitative culture. A total of 255 microorganisms were isolated from 194 positive samples by the standard quantitative procedure. A total of 85.1%, 82.5% and 72.5% agreement between direct disk diffusion, Etest and antibiotic-enriched MacConkey agar plates, respectively, and the standard procedure was observed in 64 microorganisms obtained from monomicrobial cultures that corresponded to 240 individual microorganism-antimicrobial agent combinations. Three (1.3%) and four (1.7%) very major errors for direct disk diffusion and Etest methods were observed, respectively. The antibiotic-enriched MacConkey agar plate method compared with the standard procedure demonstrated an unacceptable rate of very major (6.7%) and major errors (14.2%). Clinical evaluation of direct susceptibility tests based on the speculative impact on clinical practice by guiding patient's early treatment, if all positive cultures corresponded to infection, was correct in 79.9% for the direct disk diffusion test, 77.8% for the direct Etest method and 68.0% for antibiotic-enriched MacConkey agar plates. Direct diffusion tests (Etest or disk diffusion) applied on respiratory samples are rapid techniques that provide results comparable with standard antimicrobial susceptibility testing in <24 h.
authors.affiliation: 4th Department of Internal Medicine, Infectious Diseases Laboratory, University of Athens Medical School, Athens, Greece.
authors.forename: Flora
authors.initials: F
authors.lastname: Kontopidou
authors.forename: Irene
authors.initials: I
authors.lastname: Galani
authors.forename: Theofano
authors.initials: T
authors.lastname: Panagea
authors.forename: Anastasia
authors.initials: A
authors.lastname: Antoniadou
authors.forename: Maria
authors.initials: M
authors.lastname: Souli
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Paramythiotou
authors.forename: George
authors.initials: G
authors.lastname: Koukos
authors.forename: Irene
authors.initials: I
authors.lastname: Karadani
authors.forename: Apostolos
authors.initials: A
authors.lastname: Armaganidis
authors.forename: Helen
authors.initials: H
authors.lastname: Giamarellou
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D012634:Bodily Secretions / Q000382:microbiology*; D001980:Bronchi / Q000382:microbiology*; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D053717:Pneumonia, Ventilator-Associated / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents