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Comparison of four methods for the identification of Trichophyton benhamiae strains: Maldi-Tof MS, ITS sequencing, Diversilab® system and DermaGenius® Multiplex Real-Time PCR kit.
SACHELI, Rosalie; Ferrer Clusella, Aida; ADJETEY BAHUN, Akolé et al.
20178th trends in Medical Mycology
 

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Abstract :
[en] Background: Infections due to the zoophilic dermatophyte Trichophyton benhamiae are being more frequently diagnosed in Belgium since a few years. This species has been recently included in the T. benhamiae series together with T. concentricum, T. verrucosum and T. erinacei (De Hoog et al 2016). The strains appear in culture with a bright yellow thallus and do not easily sporulate making them difficult to identify by microscopy. Maldi-Tof MS may present an alternative to microscopic or molecular identification of this species. Molecular methods as ITS sequencing, Rep-PCR by Diversilab® system and realtime PCR by DermaGenius® kit, have been evaluated as identification methods. Methods: A total of 37 strains have been analyzed, all collected by the National Reference Center for mycosis between 2012 and 2016. Strains appearing with a yellow pigment in culture were compared to strains appearing white in culture and presenting characteristics of Trichophyton interdigitale by microscopy. All strains were characterized by Maldi-Tof MS (Bruker), ITS sequencing, rep-PCR (Diversilab® system, bioMérieux) and real-time PCR (DermaGenius® Nail multiplex kit, Pathonostics). Results: Among the 37 strains, ITS sequencing identified 10 T. benhamiae and 27 T. interdigitale. Most of the time, white strains gave rise to T. interdigitale identification while strains with yellow pigmentation were identified as T. benhamiae. However, two strains were identified as T. benhamiae but did not produce clear yellow pigmentation. DermaGenius®kit was able to detect the same 27 white strains previously identified by ITS sequencing as T. interdigitale but nor the 8 strains with yellow pigmentation nor the two white strains identified as T. benhamiae by ITS sequencing could be recognized. This is explained by the lack of specific designed primers and probes included in the kit. The Diversilab® system classified 19 white strains in a unique cluster belonging to T. interdigitale. Six strains producing yellow pigment as well as the two white strains identified as T. benhamiae by ITS sequencing belonged to a single cluster sharing only 75% of similarity with the cluster of T. interdigitale strains. Finally Maldi-Tof MS could identified14 white strains as T. interdigitale, one white strain was identified as T. benhamiae and 4 analyzed strains producing a yellow pigment were identified as T. benhamiae (51,5% of correct identification). T. interdigitale strains and T. benhamiae strains formed two different clusters easily visualized on the dendrogram. Conclusion: ITS sequencing is the method of choice to identify T. benhamiae strains. The DermaGenius® kit is not yet able to detect this emerging species. Improvement of this method is necessary as the number of T. benhamiae isolated in Europe is increasing. Rep-PCR by Diversilab® is a typing method able to classify the strains into two different clusters of strains belonging to T. interdigitale and T. benhamiae, sharing few similarities and justifying the change of classification of T. benhamiae outside the ancient T. mentagrophytes complex. Finally, Maldi-Tof MS in our settings could identify only 50% of T. benhamiae strains and improvement of the extraction method is necessary to increase the method efficiency.
Disciplines :
Microbiology
Author, co-author :
SACHELI, Rosalie  ;  Centre Hospitalier Universitaire de Liège - CHU > Service de microbiologie clinique
Ferrer Clusella, Aida ;  Université de Liège - ULiège > conv. Erasmus en médecine
ADJETEY BAHUN, Akolé ;  Centre Hospitalier Universitaire de Liège - CHU > Service de microbiologie clinique
DARFOUF, Rajae ;  Centre Hospitalier Universitaire de Liège - CHU > Service de microbiologie clinique
MEEX, Cécile ;  Centre Hospitalier Universitaire de Liège - CHU > Service de microbiologie clinique
HAYETTE, Marie-Pierre ;  Centre Hospitalier Universitaire de Liège - CHU > Service de microbiologie clinique
Language :
English
Title :
Comparison of four methods for the identification of Trichophyton benhamiae strains: Maldi-Tof MS, ITS sequencing, Diversilab® system and DermaGenius® Multiplex Real-Time PCR kit.
Publication date :
October 2017
Event name :
8th trends in Medical Mycology
Event place :
Belgrade, Serbia
Event date :
6-9 octobre 2017
Audience :
International
Available on ORBi :
since 09 December 2017

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