Continuous increase of Trichophyton tonsurans at the expense of Microsporum audouinii var. langeronii as a cause of tinea capitis in the urban area of Paris: A five-year long study

Tinea capitis (TC) remains a public health in pediatric population in urban areas. The dermatophytes responsible can be divided into three major groups: anthropophilic, zoophilic, and geophilic species. Our objective was to analyze the recent epidemiology of TC in our hospital in Paris, France. We included all the patients seen from October 2010 to September 2015 in our laboratory for suspicion of TC. Suspected lesions were sampled and epidemiological data were recorded. After a direct microscopic examination, hair samples were seeded on Sabouraud medium agar slant and kept 3 weeks at 26 °C. The species identification was based on macroscopic and microscopic examination. We obtained 3372 samples from 3090 patients (sex ratio 0.93; median age: 8 years, range: 1 month-89 years). We observed 36% of infections, with an overrepresentation of young boys (71%) and 7.5% of patients were defined as carriers. Three anthropophilic species were predominant (96%): Trichophyton soudanense , Trichophyton tonsurans , and Microsporum langeronii . For a given family ( n  = 233.2 to 6 members), the same species was identified when several TCs were diagnosed except for five. Therefore, we counted one family as one case to analyze the evolution over time. Globally, the incidence of T. tonsurans increased over time and it was the first species isolated in 2014. When considering the geographical origin, we observed a continuous increase of T. tonsurans in the sub-Saharan African patients, mainly at the expense of M. langeronii, T. soudanense remaining quite stable ( Fig. 1 ). In the Caribbean patients, T. tonsurans remained majority, although T. soudanense was present, suggesting transmission between communities. This increase of T. tonsurans could be due to a better fitness of this species for transmission between individuals through community contacts or by common hairdressers. Another explanation could be the less susceptibility of T. tonsurans to griseofulvin, the main agent used in the pediatric population to treat TC. This study showed that T. tonsurans became in 2014 the major agent of TC in the urban area of Paris, as already reported in London. Although British and American guidelines supporting terbinafine as the first choice to treat Trichophyton TCs, the French recommendation is griseofulvin since terbinafine does not have governmental approval in children. These recommendations could be challenged in case of continuous increase of T. tonsurans in TC.