title: Detection of methicillin resistance in Staphylococcus aureus isolated from pediatric patients: is the cefoxitin disk diffusion test accurate enough?
abstract: We evaluated the performance of several methods for the detection of methicillin resistance in Staphylococcus aureus using 101 clinical S. aureus isolates from pediatric patients in a tertiary hospital in Brazil; 50 isolates were mecA-positive and 51 were mecA-negative. The Etest and oxacillin agar screening plates were 100% sensitive and specific for mecA presence. Oxacillin and cefoxitin disks gave sensitivities of 96 and 92%, respectively, and 98% specificity. Alterations of CLSI cefoxitin breakpoints increased sensitivity to 98%, without decreasing specificity. Our results highlight the importance of a continuing evaluation of the recommended microbiological methods by different laboratories and in different settings. If necessary, laboratories should use a second test before reporting a strain as susceptible, especially when testing strains isolated from invasive or serious infections. With the new (2007) CLSI breakpoints, the cefoxitin-disk test appears to be a good option for the detection of methicillin resistance in S. aureus.
authors.affiliation: Division of Pediatric Infectious Diseases, Department of Pediatrics, Santa Casa University Hospital, Brazil.
authors.forename: M J
authors.initials: MJ
authors.lastname: Mimica
authors.forename: E N
authors.initials: EN
authors.lastname: Berezin
authors.forename: R L B
authors.initials: RL
authors.lastname: Carvalho
authors.forename: I M
authors.initials: IM
authors.lastname: Mimica
authors.forename: L M J
authors.initials: LM
authors.lastname: Mimica
authors.forename: M A P
authors.initials: MA
authors.lastname: Sáfadi
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.forename: H H
authors.initials: HH
authors.lastname: Caiaffa-Filho
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis; D002440:Cefoxitin / Q000494:pharmacology*; D002648:Child; D004058:Diffusion; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000379:methods; D010068:Oxacillin / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D015203:Reproducibility of Results; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D002440:Cefoxitin; D010068:Oxacillin