Epidemiological aspects and genotypic characterization of strains of Microsporum audouinii isolated in the context of a Belgian National survey on anthropophilic tinea

Objectives
The last two years, clinical cases of tinea capitis caused by Microsporum audouinii (M. audouinii), have increased in Belgium. To better understand the emergence of this species in the population, the Belgian National Reference Center (NRC) for dermatophytes launched a national survey in 2013. Epidemiological aspects and genotypic characterization of the strains were included.
Methods
The study was conducted from March 2013 up to February 2014. All Belgian laboratories were asked to send M. audouinii strains isolated from hair to the NRC with a form to fill in including epidemiological informations. The fungal strains were identified by microscopy or ITS sequencing in case of doubt. The genotypic analysis was performed by the DiversiLab® system (bioMérieux) for DNA fingerprinting and analysis. Epidemiological informations were analyzed with the help of a biostatistician.

Results
Among the collected isolates, 97 strains have been currently confirmed as M. audouinii. Preliminary analysis of the epidemiological characteristics of the infected population shows that the main age category concerns 5-9 year-old children (84%) with a sex-ratio M/F of 1.95. Data concerning the geographic origin of the family have been obtained in only 45.8% of the cases. It reveals that strains have been mainly isolated from patients with a Belgian nationality (77%) suggesting bias in the data collection. The geographic origin of the remaining group (23%) includes several African countries. The genotypic analysis led to the distinction of 3 genotypic variants of M. audouinii. One of these variants was exclusively recovered from South Belgium (11 strains). The major group was composed of 85 strains, well distributed in different Belgium locations. The last group contains only one strain but this strain was significantly different from the two other variants.

Conclusion
The automated typing DiversiLab® system proved to be an easy and efficient method to investigate the molecular epidemiology of dermatophytes infections. These preliminary results show that, through Belgium, several groups of isolates co-exist for M. audouinii providing evidence of genetic heterogeneity. At this time all epidemiological informations have not yet been assessed while 35 strains of M. audouinii remain to be analysed genotypically to give definitive conclusions.