Invasive fungal infections remain a serious threat to immunocompromised hosts. Current diagnostic methods, including fungal culture and antigen detection, are slow and often lack specificity. Rapid diagnostic tools with increased sensitivity and specificity should improve care of patients with invasive fungal infection. Recently, Luminex Molecular Diagnostics (Toronto, Canada) developed 23 analyte specific reagents (ASR) for the detection of the most common clinically relevant fungi. The objective of this study was to evaluate the sensitivity and specificity of a subset of these ASRs on fungal isolates and clinical specimens.
78 previously characterized fungal isolates (clinical isolates and ATCC strains) and 31 blood culture specimens were tested. DNA extraction was performed on the MagNA Pure instrument (Roche, Indianapolis, IN), followed by amplification and hybridization on MyCycler (Bio-rad, Hercules, CA) and detection on a Luminex 200 instrument. The isolates were tested using either a Candida 7-plex panel (C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. lusitaniae, C. guillermondii, and C. krusei) or a Mold 12-plex panel (A. fumigatus, A. flavus, A. niger, A. terreus, S. prolificans, S. apiospermum, F. oxysporum/F. solani, R. arrhizus, R. microsporus, Mucor indicus and C. bertholletiae). Tremella fuciformis was used as an external run control. Serial dilutions of amplified C. albicans and A. fumigatus DNA were also tested to establish a lower limit of detection (LLOD).
The Candida 7-plex panel correctly identified all candida isolates as confirmed by fungal culture and biochemical tests for a sensitivity and specificity of 100%. The Mold 12-plex panel correctly identified all mold isolates tested except for A. niger. Fungal isolates of Rhizopus and Mucor species were not detected either although those could represent species other than those targeted by the ASR. The LLOD for both C. albicans and A. fumigatus was 1 pg. #
The excellent sensitivity and specificity of the xTAG Luminex fungal ASR makes them an attractive option for diagnosis of fungal infection. Further evaluation will be necessary to confirm the sensitivity of some of the mold ASRs. Implementation of these ASR will allow same day detection of fungal DNA in clinical specimens.
Full conference title:
- ASM 111th (2011)