title: Detection of heterogeneous vancomycin-intermediate Staphylococcus aureus isolates using a combination of δ-hemolysis assay and Etest.
abstract: This study evaluated the δ-hemolysis assay for detection of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) isolates. The assay was performed using Columbia or trypticase soy blood agar plates without vancomycin at 37°C with 5% CO2, and the test isolate was streaked perpendicularly 1mm away from S. aureus RN4220. One hundred thirty-eight methicillin-resistant S. aureus (MRSA) bloodstream isolates with vancomycin MICs of 0.75-2 μg/mL were screened for hVISA by the δ-hemolysis assay and Etest glycopeptide resistance detection (GRD) method. The δ-hemolysis assay could be read at 24h and was more sensitive and specific than the Etest GRD at 24h and 48 h for detection of hVISA. Because most hVISA isolates have a vancomycin MIC of 2 μg/mL, we recommend screening MRSA isolates first using Etest for those with an MIC of 2 μg/mL and then performing the δ-hemolysis assay on these isolates for hVISA.
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan; Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Shih-Cheng
authors.initials: SC
authors.lastname: Chang
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
authors.forename: Tsui-Ping
authors.initials: TP
authors.lastname: Liu
authors.affiliation: Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Children's Hospital and Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Chih-Jung
authors.initials: CJ
authors.lastname: Chen
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
authors.forename: Lee-Chung
authors.initials: LC
authors.lastname: Lin
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan; Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan. Electronic address: janglu45@gmail.com.
authors.forename: Jang-Jih
authors.initials: JJ
authors.lastname: Lu
mesh_terms: D000465:Algorithms; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis*; D001431:Bacteriological Techniques / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism; D004361:Drug Tolerance; D006460:Hemolysin Proteins / Q000032:analysis*; D006801:Humans; D012680:Sensitivity and Specificity; D013211:Staphylococcus aureus / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*; D013696:Temperature; D013997:Time Factors; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D002245:Carbon Dioxide; D014640:Vancomycin; C025994:delta hemolysin protein, Staphylococcus aureus
keywords: Heterogeneous vancomycin-intermediate; Methicillin-resistant; Staphylococcus aureus; δ-Hemolysis