Evaluation of the peptide nucleic acid fluorescence in situ hybridisation technology for yeast identification directly from positive blood cultures: an Italian experience

Abstract

Fungaemia is an increasing nosocomial pathology. The 'gold standard' for detection of fungaemia is blood culture, but it is time-consuming and its sensitivity for early detection is low. On the other hand, yeasts present different antifungal sensitivity patterns to be quickly detected to allow an effective treatment. The aim of this study was to evaluate the diagnostic performances of PNA-FISH to directly identify yeasts from blood cultures and to compare results with those obtained by culture. A total of 176 blood cultures positive for yeasts at direct Gram stain and 24 negative blood cultures as control collected from 15 Italian hospitals, included in a network coordinated by the Medical Mycology Committee, Italian Society of Clinical Microbiology (AMCLI), were examined both by culture and PNA-FISH technology. Sensitivity of the PNA-FISH technique evaluated for five Candida species was 99.3% and specificity, 100%. Distinguishing which yeast is implicated in fungaemia and whether the infection is caused by multiple species are important for the selection of antifungal therapy. The PNA-FISH technique is a very useful approach because the test discriminates between groups of Candida species with different susceptibility pattern, particularly against azoles and echinocandins, with only a 90-minute turn-around time after the Gram-stain reading.

Comparative analysis of Gram's stain, PNA‐FISH and Sepsityper with MALDI‐TOF MS for the identification of yeast direct from positive blood cultures

“…The most successful method was the PNA‐FISH YTL assay achieving 96% (48/50) success. These findings are supported by two further studies publishing 96% and 99.3% success rates . Gram's stain analysis identified 72% (36/50) of the yeast isolates.…”

“…These findings are supported by two further studies publishing 96% and 99.3% success rates. 27,28 Gram's stain analysis identified 72% (36/50) of the yeast isolates. MALDI-TOF MS identified 56% (28/50) using manufacturers log score thresholds for blood culture analyses increasing to 76% (38/50) when inhouse parameters were applied.…”

“…Contrasting Gram's stain and MALDI-TOF MS, the success of the PNA-FISH YTL assay was attributed to the minimal technical expertise necessary to perform the assay and the high specificity of the assay for its target molecule, exceeding 95%. 27,28,39,40 The highly visible fluorescent signals seen using microscopy enable accurate results interpretation requiring a small amount of training and hands on time. Non-specific fluorescence or cross reaction of the YTL probes with human blood components was not observed.…”

Fish

“…An Italian study also showed that out of 176 candidemias, the YTL was rapid by 3 days and was accurate [70]. Another study showed that the YTL improved the accuracy of antifungal therapy from 76 to 95%, but only showed minimal antifungal cost savings and no impact on hospital length of stay [71].…”

Broad-Range Direct Detection and Identification of Fungi by Use of the PLEX-ID PCR-Electrospray Ionization Mass Spectrometry (ESI-MS) System

“…Recently, molecular methods such as real-time PCR and peptide nucleic acid fluorescent hybridization probes have become important tools for the detection of fungal pathogens in the clinical microbiology laboratory (4)(5)(6)(7). Although these methods can significantly reduce the turnaround time (TAT) for results, they require the clinician to make an educated guess as to the potential cause of infection since they often target only a single pathogen or a small group of related pathogens (8).…”