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Journal of Clinical Microbiology, October 2000, p. 3735-3742, Vol. 38, No. 10
National Diagnostics Centre, BioResearch
Ireland, National University of Ireland, Galway,
Ireland,1 and Innogenetics NV, Ghent,
Belgium2
Received 22 February 2000/Returned for modification 27 March
2000/Accepted 2 June 2000
We report on a reverse-hybridization line probe assay (LiPA) which
when combined with PCR amplification detects and identifies clinically
significant fungal pathogens including Candida,
Aspergillus, and Cryptococcus species. DNA
probes have been designed from the internal transcribed-spacer (ITS)
regions of Candida albicans, Candida
parapsilosis, Candida glabrata, Candida
tropicalis, Candida krusei, Candida
dubliniensis, Cryptococcus neoformans,
Aspergillus fumigatus, Aspergillus versicolor,
Aspergillus nidulans and Aspergillus flavus.
The probes were incorporated into a LiPA for detection of biotinylated
ITS PCR products, and the specificity of the probes was evaluated. We
established LiPA detection limits for ITS 1 and for full ITS amplicons
for genomic DNA from C. albicans, A. fumigatus,
and C. neoformans. Further evaluation of the LiPA was carried out on clinical fungal isolates. One hundred twenty-seven isolates consisting of dimorphic yeasts and dermatophytic and filamentous fungi were tested by the LiPA, which correctly identified 77 dimorphic yeasts and 23 of the filamentous isolates; the remaining 27 isolates represented species of fungi for which probes were not
included in the LiPA. The fungal-PCR-LiPA technology was applied to
blood samples inoculated with Candida cells which were
pretreated by minibead beating to mechanically disrupt the cells, with
the DNA extracted by either a previously described guanidium
thiocyanate-silica method or the commercially available QIAmp tissue
kit. PCR amplification of the extracted DNA and subsequent DNA probe
hybridization in the LiPA assay yielded detection limits of 2 to 10 cells/ml. An internal standard control was included in the PCR
amplification to monitor for PCR inhibition. This fungal PCR-LiPA assay
is robust and sensitive and can easily be integrated into a
clinical-testing laboratory with the potential for same-day diagnosis
of fungal infection.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Development of a PCR-Based Line Probe Assay for
Identification of Fungal Pathogens
*
Corresponding author. Mailing address: National
Diagnostics Centre, BioResearch Ireland, National University of
Ireland, Galway, Ireland. Phone: 353-91-586559. Fax: 353-91-586570. E-mail: majella.maher{at}nuigalway.ie.
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