Investigation of a dermatophytosis outbreak in a kindergarten in Doubs, France, June 2022.

Background: Microsporum audouinii, an anthropophilic dermatophyte has recently reemerged in several European countries (such as France).

Aim: To describe the epidemiological and microbiological investigations into several reported cases of dermatophytosis to the public health authorities in May 2022 in a kindergarten in the Doubs department (eastern France).

Methods: All children with clinical signs underwent a clinical examination and mycological investigation of skin or scalp samples taken onsite at the kindergarten. Several diagnosis methods were used: Wood's lamp examination, classical process (direct examination associated to culture) and molecular techniques. An epidemiological survey by questionnaire was also performed to collect individual exposure data.

Results: Fifteen children presented lesions during the clinical examination. Therapy was prescribed for nine children based on the 2021 recommendations of the French Society of Dermatology. Microsporum canis was initially diagnosed by the classical process. This identification was not confirmed by epidemiological information (absence of direct contact with animals) and molecular techniques. Finally, Microsporum audouinii was isolated in six children (two positive Wood's lamp examinations) and one staff member.

Conclusion: Species identification allowed us to (1) update the therapeutic strategy (all children were treated successfully) and (2) be more vigilant regarding the risk of human-to-human transmissions. The management of intrafamilial transmissions requires collaboration with healthcare practitioners to clinically examine family members, prescribe laboratory investigations, and reiterate the hygiene measures. This study confirmed the importance of combining field epidemiological investigations and microbiological examinations when managing dermatophytosis outbreaks.