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Title: Inducible resistance to clindamycin in Staphylococcus aureus: validation of Vitek-2 against CLSI D-test.
Austin Authors: Gardiner, B J;Grayson, M Lindsay ;Wood, G M
Affiliation: Infectious Diseases Department, Austin Health, Victoria, Australia
Issue Date: 1-Feb-2013
Publication information: Pathology; 45(2): 181-4
Abstract: Inducible resistance to clindamycin in Staphylococcus aureus is common but not easily identified by routine testing, and can result in treatment failure if not detected. The gold standard method is the D-test described by the Clinical and Laboratory Standards Institute (CLSI). The Vitek-2 AST-P612 card contains an 'inducible clindamycin resistance' (ICR) test. We aimed to determine the accuracy of the Vitek-2 ICR test compared to the D-test.Isolates of erythromycin non-susceptible, clindamycin susceptible Staphylococcus aureus were identified. Routine antimicrobial susceptibility testing was performed using the Vitek-2 AST-P612 card, including the ICR test, and compared against the D-test.217 isolates were obtained. All of the 191 isolates that were ICR positive were D-test positive. Of the 27 ICR negative isolates, 10 (37%) were D-test positive [9 methicillin-sensitive S. aureus (MSSA), 1 methicillin-resistant S. aureus (MRSA)]. This correlates with a specificity of 100%, sensitivity of 95%, positive predictive value of 100%, and negative predictive value of 72%.The ICR test is reliable in the presence of a positive result; however there is a false negative rate of approximately one in four. This will lead to susceptibility reporting errors, with potentially serious clinical implications. A negative ICR should be confirmed by CLSI D-test before reporting clindamycin as susceptible where the organism is not susceptible to erythromycin.
Gov't Doc #: 23277176
DOI: 10.1097/PAT.0b013e32835cccda
Type: Journal Article
Subjects: Anti-Bacterial Agents.pharmacology
Bacterial Typing Techniques.methods
Drug Resistance, Bacterial.drug effects
Microbial Sensitivity Tests
Predictive Value of Tests
Reagent Kits, Diagnostic
Reproducibility of Results
Staphylococcal Infections.diagnosis.drug therapy.microbiology
Staphylococcus aureus.drug effects.genetics.isolation & purification
Appears in Collections:Journal articles

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