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Fingertip contamination after a brief touch of tinea capitis lesions caused by Microsporum canis

DEAR EDITOR, Tinea capitis (TC) is a common dermatophyte infection primarily affecting children. The causative pathogens belong to two genera: Trichophyton and Microsporum. Although there is great local variation in the epidemiology of TC worldwide, Trichophyton tonsurans is currently the most common cause of TC, with Microsporum canis second. M. canis is a zoophilic ectothrix species, and remains the predominant causative organism in many countries in the Mediterranean area. The most important sources of M. canis infection are cats and dogs, and it is not considered to spread from humans. In our study we evaluated fingertip contamination, which may lead to human transmission of M. canis infection from patients with TC. Children with TC confirmed by potassium hydroxide microscopy and fungal culture entered the study. In order to evaluate the potential infectiveness of the disease, we investigated the attending dermatologist and parents of children with TC, who served as the objects of the study. After cleaning their hands with alcohol 95% and with antiseptic soap and water, they briefly touched the patient’s scalp lesions and then applied their fingertips to a Petri dish containing Sabouraud dextrose agar (Novamed, Jerusalem, Israel) that contained chloramphenicol or streptomycin and penicillin to prevent contamination. Identification of the fungus was on the basis of morphological characteristics of the different fungi. The study was carried out according to the principles of the Declaration of Helsinki and was approved by the local ethics committee. Ninety children aged 1–12 years, mean age 6 4 years, with TC entered the study. Forty-four patients were infected by T. violaceum, 41 patients with M. canis, three with T. mentagrophytes and two with T. rubrum. Positive mycological culture taken from the fingertips was found in 29 (66%) T. violaceum cases, 33 (80%) cases of M. canis, all three cases of T. mentagrophytes and both cases of T. rubrum (Table 1). TC is a dermatophyte infection of the scalp commonly affecting prepubertal children. The degree of disease transmission depends on the type of dermatophyte isolated, the most contagious being the ectothrix anthropophilic species. Such species are confined largely to human skin and generally spread via close human contact and by hairbrushes, hats and clothing. They can spread rapidly and often cause epidemics in schools. M. canis is a common causative organism for TC worldwide; the most important M. canis carriers are pets, mainly cats and dogs, and it is considered not to spread from human to human. Only a few reports have pointed out the possibility of transmission by use of a shared contaminated hairbrush, by contact with fomites or by direct physical contact with an infected person. Takwale et al. described TC in two elderly women, transmitted at their hairdresser. Yu et al. reported an outbreak of TC caused by M. canis that was isolated from patients, the carpet and a pillowcase in the school. Other cases of person-to-person infection have been reported among participants in gymnastic classes after touching an infected child. An outbreak of nosocomial ringworm involved five infants in a neonatal intensive care unit, in which the source of the contamination was a nurse infected with M. canis by her cat. Another nosocomial outbreak of tinea corporis due to M. canis infection of 24 subjects, both staff and patients, was reported. The dermatophyte was apparently introduced into the facility by a single infected patient. Likely modes of subsequent disease transmission include person-to-person contact, handling of contaminated laundry and use of a shared razor. Although according to the literature human-to-human transmission of M. canis is considered to be rare, in our study we have demonstrated that 80% of the cases showed possible infectiveness of TC. Furthermore, we have shown that TC cases caused by M. canis have a greater possible infectiveness potential compared with T. violaceum (80% vs. 66% of cases). These data should be considered mainly in outbreaks of TC caused by M. canis, and infection control measures for managing such outbreaks should be taken.