Evaluation of genetic diversity by use of DNA sequencing and PCR-AFLP with antifungal susceptibility profile for Horteaea wernekii

H. Badali, S. Mohseni, C. H. W. Klaassen, G. S. de Hoog and J. Meis


Introduction: Tinea nigra is a superficial mycosis caused by the melanized, yeast-like fungus Hortaea werneckii. The disorder has longtime been regarded as an infection and therefore H. werneckii was classified as an opportunistic organism. However, tinea nigra is subclinical, only dead keratin cells on the skin being colonized. It is an infrequent, asymptomatic infection, limited to tropical and subtropical countries. Most typically, it affects palms of hands but is occasionally found on other parts of the body. H. werneckii show differences in levels of disorder and resistance to antifungal agents. Therefore, it is important to be able to correctly identify the causative organism to the species level. AFLP analysis as an identification method for medically important H. werneckii was investigated. Antifungal therapy is based on the experience of isolated case reports which mostly involved amphotericin B, itraconazole and 5-flucytosine. Therefore we have tested a total of 9 antifungal drugs against 29 isolates.
Materials and Methods: A collection of 29 isolates of H. werneckii were obtained from the CBS-KNAW Fungal Biodiversity Centre in Utrecht, The Netherlands. MICs were determined for AmB, FLU, ITC, VOC, POS, ISA, TER and MECs for CAS and ANID based on CLSI M38- A2 guidelines.
Results: AFLP patterns exhibited very clear differences among H. werneckii with other related species. The resulting MIC90s for H. werneckii strains were as follows, in increasing order: POS (0.125 mg l- 1); ITC (0.25 mg l-1); VOC (0.25 mg l-1); ISA (0.25 mg l-1); TER (0.5 mg l-1); AmB (2 mg l-1); ANID (4 mg l-1); CAS (4 mg l-1) and FLU (32 mg l-1). The new agent Isavuconazole, which is also available as an intravenous preparation, shows a good efficacy as the same as voriconazole.
Conclusion: AFLP might prove to be a reliable method for the identification of H. werneckii against other related strains which is very essential in antifungal susceptibility methods. Posaconazole and itraconazole were the most active drugs with high in vitro activity against H. werneckii. From the echinocandins tested CAS and ANID demonstrated poor in vitro activity, those drugs might not be useful for treating a range of severe fungal infections, either alone or as part of a combination therapy regimen. However their clinical effectiveness in the treatment of cerebral infection remains to be determined.

abstract No: 

    • ISHAM 18th (2012)