title: Evaluation of vancomycin susceptibility testing for methicillin-resistant Staphylococcus aureus: comparison of Etest and three automated testing methods.
abstract: We evaluated the ability of four commercial MIC testing systems (MicroScan, Vitek 2, Phoenix, and Etest) to detect vancomycin MIC values of ≤1 to ≥2 in 200 methicillin-resistant Staphylococcus aureus (MRSA) strains compared to the Clinical and Laboratory Standards Institute broth microdilution (BMD) reference methods. Compared to the BMD method, absolute agreement (0 ± dilution) was highest for the Phoenix system (66.2%) and the MicroScan turbidity method (61.8%), followed by the Vitek 2 system (54.3%). The Etest produced MIC values 1 to 2 dilutions higher than those produced by the BMD method (36.7% agreement). Of interest, the MicroScan system (prompt method) was more likely to overcall an MIC value of 1 mg/liter (74.1%), whereas the Phoenix (76%) and Vitek 2 (20%) systems had a tendency to undercall an MIC of 2 mg/liter. The ability to correctly identify vancomycin MIC values of 1 and 2 has clinical implications and requires further evaluation.
authors.affiliation: Anti-Infective Research Laboratory, Eugene Applebaum College of Pharmacy & Health Sciences, Detroit, Michigan, USA. m.rybak@wayne.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rybak
authors.forename: Celine
authors.initials: C
authors.lastname: Vidaillac
authors.forename: Helio S
authors.initials: HS
authors.lastname: Sader
authors.forename: Paul R
authors.initials: PR
authors.lastname: Rhomberg
authors.forename: Hossein
authors.initials: H
authors.lastname: Salimnia
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Briski
authors.forename: Audrey
authors.initials: A
authors.lastname: Wanger
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D057205:Automation, Laboratory / Q000379:methods; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests / Q000379:methods*; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin