American Journal of Clinical Dermatology

, Volume 18, Issue 2, pp 281–286 | Cite as

Molecular Diagnostic Techniques for Onychomycosis: Validity and Potential Application

Original Research Article



Diagnosis of onychomycosis requires positive findings by direct microscopy and fungal culture. Fungal culture is slow and difficult, with low yields. We compared two dermatophyte identification methods, one using a real-time polymerase chain reaction (PCR) method, and the other using fungal culture to validate the molecular method.


Nail specimens were collected from 149 patients with distal and lateral subungual onychomycosis who were positive for fungal elements by direct microscopy using potassium hydroxide. Each specimen was subjected to the modified real-time PCR assay of Miyajima et al. and fungal culture.


Of 149 specimens, 142 (95.3%) were positive for Trichophyton rubrum or Trichophyton mentagrophytes including Trichophyton interdigitale by PCR, while only 104 (69.8%) were positive by fungal culture performed simultaneously. No specimen was negative by PCR, but positive by culture. All specimens positive for T. rubrum or T. mentagrophytes by culture were also positive by PCR, showing complete concordance for Trichophyton species. The culture of 17 specimens yielded fungi other than T. rubrum or T. mentagrophytes, whereas PCR identified T. rubrum in 11 of these specimens. Among 28 culture-negative specimens, 23 showed T. rubrum and four showed T. mentagrophytes by PCR. PCR allowed more rapid identification of causative fungi (≤2 days vs. ≤28 days).


Real-time PCR achieved a higher dermatophyte identification rate and showed complete concordance with conventional culture for two Trichophyton species. Specimens never yielded both T. mentagrophytes and T. rubrum simultaneously, suggesting that mixed infection is uncommon.


  1. 1.
    Summerbell RC, Kane J, Krajden S. Onychomycosis, tinea pedis and tinea manuum caused by non-dermatophyte filamentous fungi. Mycoses. 1989;32:609–19.CrossRefPubMedGoogle Scholar
  2. 2.
    Malik NA, Nasiruddin, Dar NR, Khan AA. Comparison of plain potassium hydroxide mounts, fungal cultures and nail plate biopsies in the diagnosis of onychomycosis. J Coll Physicians Surg Pak. 2006;16:641–4.PubMedGoogle Scholar
  3. 3.
    Nishimoto K. An epidemiological survey of dermatomycoses in Japan, 2002. Nihon Ishinkin Gakkai Zasshi. 2006;47:103–11.CrossRefPubMedGoogle Scholar
  4. 4.
    Sei Y. 2006 Epidemiological survey of dermatomycoses in Japan. Med Mycol J. 2012;53:185–92.CrossRefPubMedGoogle Scholar
  5. 5.
    Sei Y. 2011 Epidemiological survey of dermatomycoses in Japan. Med Mycol J. 2015;56:129–35.CrossRefGoogle Scholar
  6. 6.
    Roberts DT, Taylor WD, Boyle J, British Association of Dermatologists. Guidelines for treatment of onychomycosis. Br J Dermatol. 2003;148:402–10.CrossRefPubMedGoogle Scholar
  7. 7.
    Milobratović D, Janković S, Vukičević J, et al. Quality of life in patients with toenail onychomycosis. Mycoses. 2013;56:543–51.CrossRefPubMedGoogle Scholar
  8. 8.
    Watanabe S, Mochizuki T, Isozumi K, et al. Japanese Dermatological Association guidelines for the diagnosis and treatment of dermatomycoses. Jpn J Dermatol. 2009;119:851–62 (in Japanese).Google Scholar
  9. 9.
    Jensen RH, Arendrup MC. Molecular diagnosis of dermatophyte infections. Curr Opin Infect Dis. 2012;25:126–34.CrossRefPubMedGoogle Scholar
  10. 10.
    Miyajima Y, Satou K, Uchida T, et al. Rapid real-time diagnostic PCR for Trichophyton rubrum and Trichophyton mentagrophytes in patients with tinea unguium and tinea pedis using specific fluorescent probes. J Dermatol Sci. 2013;69:229–35.CrossRefPubMedGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.Department of DermatologyTeikyo University School of MedicineTokyoJapan
  2. 2.Basic Research LaboratoriesHisamitsu Pharmaceutical Co., Inc.TsukubaJapan

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