Comparison of the Staphylococcus QuickFISH BC test with the tube coagulase test performed on positive blood cultures for evaluation and application in a clinical routine setting

E. Carretto, M. Bardaro, G. Russello, M. Mirra, C. Zuelli, D. Barbarini

Research output: Contribution to journalArticle

Abstract

Many studies demonstrate that delayed proper therapy in bloodstream infections caused by Staphylococcus aureus increases the mortality rate, emphasizing the need to shorten the turnaround time for positive blood cultures. Different techniques are currently available, from phenotypic methods to more complex tests such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF), real-time PCR (RT-PCR), and fluorescence in situ hybridization using peptide nucleic acid probes (PNA FISH). This study evaluated the performance of the Staphylococcus QuickFISH BC test (QFT), a novel FISH methodology, compared with the direct tube coagulase test (DTCT) on blood cultures exhibiting Gram-positive cocci in clusters. A total of 173 blood cultures collected from 128 different patients were analyzed using the DTCT, evaluated after both 4 and 24 h, and the QFT. A total of 179 isolates were identified using the Vitek2 system. Thirty-five out of 35 Staphylococcus aureus were correctly identified by the QFT (sensitivity = 100%), with a specificity of 100% (no green fluorescence was detected for strains different from S. aureus). The DTCT was positive after 4 h for 28 out of the 35 samples (sensitivity = 80%) and after 24 h for 31 out of the 35 samples (sensitivity = 88.57%). Among the remaining 144 isolates, one was then identified as Corynebacterium striatum and two as Micrococcus luteus. QFT identified 139 out of the 141 coagulase-negative staphylococci (CoNS) (sensitivity = 98.58%), showing again a specificity of 100% (no fluorescent red signals were detected for strains different from CoNS).Wealso discuss also the implementation process of this methodology in our setting, with particular emphasis on the workflow and the cost-effectiveness.

Original languageEnglish
Pages (from-to)131-135
Number of pages5
JournalJournal of Clinical Microbiology
Volume51
Issue number1
DOIs
Publication statusPublished - Jan 2013

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Coagulase
Staphylococcus
Staphylococcus aureus
Nucleic Acid Probes
Micrococcus luteus
Peptide Nucleic Acids
Gram-Positive Cocci
Corynebacterium
Workflow
Fluorescence In Situ Hybridization
Cost-Benefit Analysis
Real-Time Polymerase Chain Reaction
Mass Spectrometry
Lasers
Fluorescence
Blood Culture
Mortality
Infection

ASJC Scopus subject areas

  • Microbiology (medical)

Cite this

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title = "Comparison of the Staphylococcus QuickFISH BC test with the tube coagulase test performed on positive blood cultures for evaluation and application in a clinical routine setting",
abstract = "Many studies demonstrate that delayed proper therapy in bloodstream infections caused by Staphylococcus aureus increases the mortality rate, emphasizing the need to shorten the turnaround time for positive blood cultures. Different techniques are currently available, from phenotypic methods to more complex tests such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF), real-time PCR (RT-PCR), and fluorescence in situ hybridization using peptide nucleic acid probes (PNA FISH). This study evaluated the performance of the Staphylococcus QuickFISH BC test (QFT), a novel FISH methodology, compared with the direct tube coagulase test (DTCT) on blood cultures exhibiting Gram-positive cocci in clusters. A total of 173 blood cultures collected from 128 different patients were analyzed using the DTCT, evaluated after both 4 and 24 h, and the QFT. A total of 179 isolates were identified using the Vitek2 system. Thirty-five out of 35 Staphylococcus aureus were correctly identified by the QFT (sensitivity = 100{\%}), with a specificity of 100{\%} (no green fluorescence was detected for strains different from S. aureus). The DTCT was positive after 4 h for 28 out of the 35 samples (sensitivity = 80{\%}) and after 24 h for 31 out of the 35 samples (sensitivity = 88.57{\%}). Among the remaining 144 isolates, one was then identified as Corynebacterium striatum and two as Micrococcus luteus. QFT identified 139 out of the 141 coagulase-negative staphylococci (CoNS) (sensitivity = 98.58{\%}), showing again a specificity of 100{\%} (no fluorescent red signals were detected for strains different from CoNS).Wealso discuss also the implementation process of this methodology in our setting, with particular emphasis on the workflow and the cost-effectiveness.",
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AU - Carretto, E.

AU - Bardaro, M.

AU - Russello, G.

AU - Mirra, M.

AU - Zuelli, C.

AU - Barbarini, D.

PY - 2013/1

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