Multicenter Evaluation of the Staphylococcus QuickFISH Method for Simultaneous Identification of Staphylococcus aureus and Coagulase-Negative Staphylococci Directly from Blood Culture Bottles in Less than 30 Minutes

Abstract

A novel rapid peptide nucleic acid fluorescence in situ hybridization (FISH) method, Staphylococcus Quick FISH, for the direct detection of Staphylococcus species from positive blood culture bottles was evaluated in a multicenter clinical study. The method utilizes a microscope slide with predeposited positive- and negative-control organisms and a self-reporting 15-min hybridization step, which eliminates the need for a wash step. Five clinical laboratories tested 722 positive blood culture bottles containing Gram-positive cocci in clusters. The sensitivities for detection of Staphylococcus aureus and coagulase-negative staphylococci (CoNS) were 99.5% (217/218) and 98.8% (487/493), respectively, and the combined specificity of the assay was 89.5% (17/19). The combined positive and negative predictive values of the assay were 99.7% (696/698) and 70.8% (17/24), respectively. Studies were also performed on spiked cultures to establish the specificity and performance sensitivity of the method. Staphylococcus Quick FISH has a turnaround time (TAT) of <30 min and a hands-on time (HOT) of <5 min. The ease and speed of the method have the potential to improve the accuracy of therapeutic intervention by providing S. aureus /CoNS identification simultaneously with Gram stain results.

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

“…According to these considerations, the sensitivity of the method in CoNS detection is 97.14%, but if we exclude for the computation the two Micrococcus lutes strains, the performance of the QFT increases to 98.58% and appears even more impressive. The data are in overall agreement with the sensitivity revealed in the validation study (11).…”

“…It has to be expected that the manufacturer will broaden the number of pathogens this new technology can detect. Our study represents an early clinical laboratory evaluation of the first product available on this platform after the validation paper of Deck et al (11). This molecular procedure is based on the PNA FISH methodology with shortened fixation and hybridization phases and elimination of the washing steps.…”

“…The pathogen detection requires a maximum of 20 min, allowing the clinical microbiologist to report the obtained identification (ID) together with initial Gram stain result. This technique has been recently validated (11). This study evaluates the performance of this new FISH methodology, comparing it with the DTCT evaluated after 4 h (DTCT4) and 24 h (DTCT24), on different sets of blood cultures showing Gram-positive cocci in clusters (GPCC), collected in a 3-month period in the IRCCS Arcispedale Santa Maria Nuova of Reggio Emilia, Italy, in order to assess its usefulness in clinical practice and implementation in routine laboratory workflow.…”

“…A real-time PCR approach is available (Gene X-pert MRSA/SA; Cepheid, Sunnyvale, CA); the method is really easy to perform and seems to have an exquisite sensitivity (10), but its main disadvantage is that it is too expensive, especially for settings managing a large amount of samples. The direct tube coagulase test (DTCT), performed from positive blood cultures, is used for discrimination between S. aureus and CoNS strains; this test is cheap and easy to perform and possesses high specificity but a great inconsistency in sensitivity, ranging from 60% to 100% (11,12).…”

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.…”