title: Investigation of Staphylococcus aureus isolates identified as erythromycin intermediate by the Vitek-1 System: comparison with results obtained with the Vitek-2 and Phoenix systems.
abstract: We identified 69 Staphylococcus aureus isolates that were erythromycin intermediate as reported by the Vitek-1 system using the GPS-105 card. Of the 57 strains that were available for further testing, all were erythromycin resistant by broth microdilution and the Phoenix system, while the Vitek-2 system identified 55 of 57 strains (96%) as erythromycin resistant. The majority of isolates (54 of 57 [95%]) exhibited the inducible MLS (macrolide-lincosamide-streptogramin family) phenotype, as shown by the double-disk test. We recommend that all S. aureus strains determined as erythromycin intermediate by the Vitek-1 system be interpreted as resistant to erythromycin.
authors.affiliation: Department of Microbiology, Mount Sinai Hospital, and Toronto Medical Laboratories, Toronto, Ontario, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tang
authors.forename: Donald E
authors.initials: DE
authors.lastname: Low
authors.forename: Sandra
authors.initials: S
authors.lastname: Atkinson
authors.forename: Karen
authors.initials: K
authors.lastname: Pike
authors.forename: Aisha
authors.initials: A
authors.lastname: Ashi-Sulaiman
authors.forename: Andrew
authors.initials: A
authors.lastname: Simor
authors.forename: Susan
authors.initials: S
authors.lastname: Richardson
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Willey
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000295:instrumentation / Q000379:methods; D011933:Reagent Kits, Diagnostic; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D011933:Reagent Kits, Diagnostic; D004917:Erythromycin