title: Multicenter study to determine disk diffusion and broth microdilution criteria for prediction of high- and low-level mupirocin resistance in Staphylococcus aureus.
abstract: Mupirocin susceptibility testing of Staphylococcus aureus has become more important as mupirocin is used more widely to suppress or eliminate S. aureus colonization and prevent subsequent health care- and community-associated infections. The present multicenter study evaluated two susceptibility testing screening methods to detect mupirocin high-level resistance (HLR), broth microdilution (BMD) MICs of >or=512 microg/ml, and a 6-mm zone diameter for a disk diffusion (DD) test with a 200-microg disk. Initial testing indicated that with Clinical and Laboratory Standards Institute methods for BMD and DD testing, the optimal conditions for the detection of mupirocin HLR were 24 h of incubation and reading of the DD zone diameters with transmitted light. Using the presence or absence of mupA as the "gold standard" for HLR, the sensitivity and specificity of a single-well 256 microg/ml BMD test were 97 and 99%, respectively, and those for the 200-microg disk test were 98 and 99%, respectively. Testing with two disks, 200 microg and 5 microg, was evaluated for its ability to distinguish HLR isolates (MICs >or= 512 microg/ml), low-level-resistant (LLR) isolates (MICs = 8 to 256 microg/ml), and susceptible isolates (MICs <or= 4 microg/ml). Using no zone with both disks as an indication of HLR and no zone with the 5-microg disk plus any zone with the 200-microg disk as LLR, only 3 of the 340 isolates were misclassified, with 3 susceptible isolates being classified as LLR. Use of standardized MIC or disk tests could enable the detection of emerging high- and low-level mupirocin resistance in S. aureus.
authors.affiliation: Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. jms1@cdc.gov
authors.forename: Jana M
authors.initials: JM
authors.lastname: Swenson
authors.forename: Betty
authors.initials: B
authors.lastname: Wong
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Simor
authors.forename: Richard B
authors.initials: RB
authors.lastname: Thomson
authors.forename: Mary Jane
authors.initials: MJ
authors.lastname: Ferraro
authors.forename: Dwight J
authors.initials: DJ
authors.lastname: Hardy
authors.forename: Janet
authors.initials: J
authors.lastname: Hindler
authors.forename: James
authors.initials: J
authors.lastname: Jorgensen
authors.forename: L Barth
authors.initials: LB
authors.lastname: Reller
authors.forename: Maria
authors.initials: M
authors.lastname: Traczewski
authors.forename: Linda K
authors.initials: LK
authors.lastname: McDougal
authors.forename: Jean B
authors.initials: JB
authors.lastname: Patel
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D016712:Mupirocin / Q000494:pharmacology*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009687:Nuclear Proteins; C480380:mupA protein, Staphylococcus aureus; D016712:Mupirocin
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