The Pathogen Identification Of Zoonotic Dermatophytosis And Antifungal Susceptibility Test In Vitro

Objective: To investigate the distribution of pathogenic dermatophyte species and discuss the sensitivity of dermatophyte to commonly-used antifungal drugs by means of analyzing the clinical features and identifying the pathogen of zoonotic dermatophytosis.Methods: 1. We collected clinical data of zoonotic dermatophytosis in the Affiliated Hospital of North Sichuan Medical College(from Oct. 2013 to Nov. 2014). The dermatophytes isolated from patients and related animals were identified by morphological and biochemical methods. The DNAs of dermatophytes were amplified by the primer(GACA)4. Then, randomly amplified polymorphic DNA(RAPD) method was also used to confirm the homology of pathogen between strains isolated from patients and related animals. 2. According to the M38-A2 protocol promulgated by Clinical and Laboratory Standards Institute(CLSI), the minimal inhibitory concentrations(MIC) of those isolated dermatophytes to Griseofulvin(GRI), Itraconazole(ICZ), Terbinafine(TBR) and Fluconazole(FLU) were determined.Results: 1. Among the 32 outpatients with zoonotic dermatophytosis, the ages of the patients range from 3 months to 77 years, the average and median age is 22.71±21.19 years, and the proportion of male and female is 1:1.67. 37.5% of the patients are under 10 years old. Most of the patients(75%) have two or more lesions, and 81.25% of the patients have the history of application of topical therapy. 59.4% of the patients come from rural areas. 2. Three dermatophyte species were identified from 57 strains, which were Microsporum canis(M.canis), Trichophyton mentagrophytes(T. mentagrophytes) and Microsporum gypseum(M. gypseum). The most species identified were M.canis(65.6%), followed by T. mentagrophytes(18.7%) and M. gypseum(15.6%). All the patients and related animals shared the same pathogen. The main source of infection was cats, followed by dogs and rabbits. 3. By RAPD, strains isolated from patients and related animals were demonstrated as the same strain. 4. Based on M38-A2 protocol promulgated by CLSI, reference susceptibility was determined for GRI, ICZ, TBR and FLU. The test shows that the MIC concentration ranges of M.canis are respectively as follows: 0.125-4μg/ml, 0.0313-1μg/ml, 0.002-0.0313μg/ml and 2-32μg/ml. The MICs of T.mentagrophytes are respectively 0.0625-1μg/ml, 0.0313-0.5μg/ml, 0.001-0.0625μg/ml and 4-32μg/ml. The MICs of M. gypseum are respectively 0.0313-2μg/ml, 0.0625-1μg/ml, 0.0039-0.0625μg/ml and 0.5-16μg/ml.Conclusions: 1. Most of the zoonotic dermatophytes are M. canis, followed by T. mentagrophytes and M. gypseum. The most common infective source is cats,followed by dogs and rabbits. 2. Even if human and related animals suffer from dermatophytosis at the same time, chances are that it is not zoonotic dermatophytosis. 3. The antifungal susceptibility test in vitro of M.canis, T.mentagrophytes and M. gypseum shows that TBR has the best antifungal effect, then followed by ICZ, GRI, and FLU.