[en] Background
Microsporum audouinii (M. audouinii) is an anthropophilic dermatophyte responsible for tinea capitis in young children. Infections caused by this species are very contagious and are responsible for outbreaks in schools and communities. Different proteases are produced by dermatophytes to digest tissue keratin. Among these proteases metalloproteases (Mep) have already been described as potential virulence factors in different zoonotic species such as Trichophyton mentagrophytes and Microsporum canis. In the present study, primers targeting five metalloproteases Mep1-5 have been designed to screen a large scale of Microsporum audouinii strains isolated in Belgium.
Material and methods
A total of 84 strains of M.audouinii were included in this study. This concerned 2 reference strains (IHEM 2758 and 2214) and 82 strains isolated from patients refered to the Mycology Laboratory of the University Hospital of Liègeduring the 2013-2016 period. The strains were identified as M. audouinii by microscopy and confirmed by ITS sequencing. Primers were newly designed based on nucleotide sequences of the genes MEP1-5 available in GenBank database for the close related species M. canis and using primer Blast (NCBI-NIH)
Results
Among the analyzed strains, the presence of at least one gene encoding for Mep1-5 was revealed in 93% (78/84) of the M. audouinii strains with 80 % (67/84) being positive for the five Meps (1-5). The percentage of detection was 89% (75/84) for Mep1, 88% (74/84) for Mep2 and Mep 5 and 85% (71/84) for Mep3. Finally, Mep4 was successfully amplified in 92% (77/84) of the isolates. In total, 7% (6/84) of the strains did not express any Mep gene. An internal control of amplification (ITS sequence) was also included to exclude a false negative result due to amplification inhibitors.
Conclusion
The presence of the Mep1-5 genes in M. audouinii strains circulating in Belgium was confirmed in this study. Fairly close percentages of expression of these genes let us think that all tested Meps could be implicated in the virulence process of M. audouinii strains. Next step will be the in vitro biochemical characterization of the expression of these Meps in M. audouinii. Another class of endoproteases called subtilisins has been recently considered to be involved in virulence process. Their presence will also be further checked in M. audouinii strains.
