title: Comparison of two commercial systems (Vitek and MicroScan-WalkAway) for antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates from cystic fibrosis patients.
abstract: Antimicrobial susceptibility testing of cystic fibrosis (CF) isolates of Pseudomonas aeruginosa is difficult because the organisms are often mucoid and slow-growing. This study of 498 CF strains examined the correlation of results derived from two commonly used commercial systems (Vitek, MicroScan-WalkAway) with a reference method for 10 antimicrobials. Correlation to reference results was unacceptably low for all agents and both commercial systems had a high rate of very major (false-susceptible) errors. Although mucoid strains produced a 4.8% greater intermethod error, it was not markedly different than non-mucoid strains for the Vitek System. Overall, these tested commercial systems performed poorly for CF isolates in contrast to earlier reported, high correlations with the reference methods (broth microdilution frozen panels and agar dilution) of the National Committee for Clinical Laboratory Standards, the standardized disk diffusion test, and the Etest (AB BIODISK, Solna, Sweden).
authors.affiliation: Department of Pediatrics, Division of Infectious Disease, Children's Hospital and Regional Medical Center, University of Washington, P.O. Box 5371/CH-32, Seattle, WA 98105-0371, USA. jburns@chmc.org
authors.forename: J L
authors.initials: JL
authors.lastname: Burns
authors.forename: L
authors.initials: L
authors.lastname: Saiman
authors.forename: S
authors.initials: S
authors.lastname: Whittier
authors.forename: J
authors.initials: J
authors.lastname: Krzewinski
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: D
authors.initials: D
authors.lastname: Larone
authors.forename: S A
authors.initials: SA
authors.lastname: Marshall
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media; D003550:Cystic Fibrosis / Q000382:microbiology*; D004352:Drug Resistance, Microbial; D024841:Fluoroquinolones; D006801:Humans; D007769:Lactams; D008826:Microbial Sensitivity Tests / Q000379:methods; D010641:Phenotype; D011237:Predictive Value of Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D011933:Reagent Kits, Diagnostic / Q000592:standards; D012015:Reference Standards
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D003470:Culture Media; D024841:Fluoroquinolones; D007769:Lactams; D011933:Reagent Kits, Diagnostic