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

bMany 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). We also discuss also the implementation process of this methodology in our setting, with particular emphasis on the workflow and the cost-effectiveness.

Evaluation of Three Rapid Diagnostic Methods for Direct Identification of Microorganisms in Positive Blood Cultures

“…The Staphylococcus QuickFISH assay was previously shown to be 97.1% to 99.0% sensitive and 89.5% to 100% specific for the detection of staphylococci (15,16). More recently, the Enterococcus QuickFISH assay was shown to be 97% sensitive for the detection of non-E. faecalis enterococci (38).…”

“…A number of different assays have been developed, each capable of detecting up to a maximum of 3 different species per assay. More recently, this method has been modified to incorporate a self-reporting probe design (QuickFISH), thereby eliminating the washing step and reducing the assay time to less than 30 min (15,16). The Verigene Blood Culture Gram-Positive (BC-GP) test uses array-based nanoparticle technology capable of detecting 12 different Grampositive organisms from positive blood cultures in a single assay.…”

Colorimetric Sensor Array Allows Fast Detection and Simultaneous Identification of Sepsis-Causing Bacteria in Spiked Blood Culture

“…Phenotypic methods include a coagulase tube test for staphylococci, biochemical arrays in automated identification systems, and most recently, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (4,5). Genotypic identification methods include fluorescence in situ hybridization (FISH) with peptide nucleic acid (PNA) probes for a limited number of species and several commercially available multiplex nucleic acid amplification tests (NAATs) for a broad range of species recovered from blood cultures (3,(5)(6)(7)(8). With the existing blood culture systems, the time to positive result typically ranges from 1 to 3 days, and an additional 1 to 2 days is needed for species identification with conventional methods, although MALDI-TOF MS and genotypic methods have shortened this time to hours instead of days.…”

An International, Prospective, Multicenter Evaluation of the Combination of AdvanDx Staphylococcus Quick FISH BC with mecA Xpress FISH for Detection of Methicillin-Resistant Staphylococcus aureus Isolates from Positive Blood Cultures

“…They also reported that the Staphylococcus QFISH assay turnaround time was Ͻ30 min and the hands-on time was Ͻ5 min. Likewise, Carretto et al (15) reported 100% sensitivity and specificity for S. aureus detection in their single-center evaluation, with minimal impact with respect to modifying laboratory workflow to accommodate testing. Compared to FOX testing, the mecAX test had two false-negative and one atypical, weak, green, and false-positive fluorescent result (sensitivity and specificity, 99.1 and 99.6%, respectively; Table 2).…”