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Journal of Clinical Microbiology, April 1999, p. 931-936, Vol. 37, No. 4
Department of Microbiology and PHLS Mycology
Reference Laboratory, University of Leeds and General Infirmary,
Leeds LS2 9JT, United Kingdom
Received 14 October 1998/Returned for modification 11 November
1998/Accepted 13 January 1999
Restriction fragment length polymorphisms (RFLPs) identified in the
ribosomal-DNA (rDNA) repeat were used for molecular strain differentiation of the dermatophyte fungus Trichophyton
rubrum. The polymorphisms were detected by hybridization of
EcoRI-digested T. rubrum genomic DNAs with
a probe amplified from the small-subunit (18S) rDNA and adjacent
internal transcribed spacer (ITS) regions. The rDNA RFLPs mapped to the
nontranscribed spacer (NTS) region of the rDNA repeat and appeared
similar to those caused by short repetitive sequences in the intergenic
spacers of other fungi. Fourteen individual RFLP patterns (DNA types A
to N) were recognized among 50 random clinical isolates of
T. rubrum. A majority of strains (19 of 50 [38%])
were characterized by one RFLP pattern (DNA type A), and four types
(DNA types A to D) accounted for 78% (39 of 50) of all strains. The
remaining types (DNA types E to N) were represented by one or two
isolates only. A rapid and simple method was also developed for
molecular species identification of dermatophyte fungi. The contiguous
ITS and 5.8S rDNA regions were amplified from 17 common dermatophyte
species by using the universal primers ITS 1 and ITS 4. Digestion of
the amplified ITS products with the restriction endonuclease
MvaI produced unique and easily identifiable fragment
patterns for a majority of species. However, some closely related taxon
pairs, such as T. rubrum-T. soudanense and
T. quinkeanum-T. schoenlenii could not be
distinguished. We conclude that RFLP analysis of the NTS and ITS
intergenic regions of the rDNA repeat is a valuable technique both for
molecular strain differentiation of T. rubrum and for
species identification of common dermatophyte fungi.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Species Identification and Strain Differentiation of Dermatophyte
Fungi by Analysis of Ribosomal-DNA Intergenic Spacer
Regions
*
Corresponding author. Mailing address: PHLS Mycology
Reference Laboratory, Department of Microbiology, The Old Medical
School, Thoresby Place, University of Leeds, Leeds LS2 9JT,
England. Phone: 44 113 233 5598. Fax: 44 113 233 5640. E-mail:
micrb{at}leeds.ac.uk.
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