Comparison of peptide nucleic acid fluorescence in situ hybridization assays with culture-based matrix-assisted laser desorption/ionization-time of flight mass spectrometry for the identification of bacteria and yeasts from blood cultures and cerebrospinal fluid cultures

Abstract

Peptide nucleic acid fluorescence in situ hybridization (PNA FISH) is a molecular diagnostic tool for the rapid detection of pathogens directly from liquid media. The aim of this study was to prospectively evaluate PNA FISH assays in comparison with culture-based matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) identification, as a reference method, for both blood and cerebrospinal fluid (CSF) cultures, during a 1-year investigation. On the basis of the Gram stain microscopy results, four different PNA FISH commercially available assays were used ('Staphylococcus aureus/CNS', 'Enterococcus faecalis/OE', 'GNR Traffic Light' and 'Yeasts Traffic Light' PNA FISH assays, AdvanDx). The four PNA FISH assays were applied to 956 positive blood cultures (921 for bacteria and 35 for yeasts) and 11 CSF cultures. Among the 921 blood samples positive for bacteria, PNA FISH gave concordant results with MALDI-TOF MS in 908/921 (98.64%) samples, showing an agreement of 99.4% in the case of monomicrobial infections. As regards yeasts, the PNA FISH assay showed a 100% agreement with the result obtained by MALDI-TOF MS. When PNA FISH assays were tested on the 11 CSF cultures, the results agreed with the reference method in all cases (100%). PNA FISH assays provided species identification at least one work-day before the MALDI-TOF MS culture-based identification. PNA FISH assays showed an excellent efficacy in the prompt identification of main pathogens, yielding a significant reduction in reporting time and leading to more appropriate patient management and therapy in cases of sepsis and severe infections.

Cryptococcus gattii Infections

“…Whether MALDI-TOF MS can be successfully applied to detect cryptococci in clinical specimens such as CSF is uncertain. In a small study, 11 CSF samples were inoculated in blood culture bottles, cultured, and then analyzed by MALDI-TOF MS for bacteria and yeasts, but none of the patients had cryptococcal meningitis (355).…”

The Epidemiology and Diagnosis of Invasive Candidiasis Among Premature Infants

“…73, 74 This assay uses species-specific fluorescent probes and is capable of identifying the five most commonly isolated species of Candida within 90 minutes. 73 When viewed under a fluorescent microscope, green fluorescence is seen in the presence of C. albicans or C. parapsilosis , yellow fluorescence with C. tropicalis , and red fluorescence in the presence of C. glabrata or C. krusei .…”

“…73 When viewed under a fluorescent microscope, green fluorescence is seen in the presence of C. albicans or C. parapsilosis , yellow fluorescence with C. tropicalis , and red fluorescence in the presence of C. glabrata or C. krusei . 73, 74 For each of the probes, the sensitivity and specificity are above 90%, and this assay generally identifies blood culture isolates more quickly than the MALDI-TOF as it does not require growth on solid media. 73, 74 …”

Identification of Staphylococci Directly from Positive Blood Culture Bottles by MALDI-TOF MS System

“…KAE'ye neden olan mikroorganizmaların tanımlanma zamanını kısaltmak için gerçek zamanlı Taqman PCR, multipleks PCR, floresan in situ hibridizasyon (FISH) ve peptid nükleik asit FISH yöntemleri geliştirilmiş ve halen kullanılmaktadır. Ancak pahalı olması, uzman personel gerektirmesi ve sadece hedef alınan mikroorganizmaları tanımlayabilmesi, dezavantajları arasında sayılmakta-dır 7 .…”