الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Dermatophytes are keratinophilic fungi that belong to three genera: Epidermophyton, Microsporum and Trichophyton. The cutaneous mycoses caused by dermatophytes are called dermatophytoses and are among the most prevalent cutaneous infections. Identification of dermatophyte species and strains is essential for appropriate diagnosis and treatment of these dermatophytoses.
Routine culture-based identification depends on examination of macroscopic and microscopic morphology which is time consuming and does not differentiate between strains. This study aimed at application of both conventional and molecular methods for identification of dermatophytes causing cutaneous mycoses in Ismailia city. The study was carried out on sixty patients diagnosed as having tinea capitis, tinea corporis, tinea cruris or tinea unguium, and who was attending El Sheikh Zayed dermatological out-patient clinic, Ismailia city, Egypt.
The specimens were collected from the lesions and the laboratory work was performed in the laboratory of microbiology department, faculty of medicine, Suez Canal University and in the laboratories of Center for Medical Mycology, Case Western Reserve University and University Hospitals, Cleveland, Ohio.
All specimens were submitted for conventional identification by using KOH examination and culture-based methods, followed by molecular-based identification using PCR.
In this study, two PCR-based methods were compared for their ability to identify the obtained dermatophytes to the species and strain levels. The first method employed a two step method: PCR amplification, using ITS1 and ITS4 as primers, followed by restriction enzyme digestion using the endonuclease MvaI. The second method employed a single step approach employing the repetitive oligonucleotide (GACA)4 as a primer.
KOH was positive in 65% of the specimens, while the culture was positive in 45% for dermatophytes, 18.3% for Candida and negative in the remaining specimens 36.7 %.
It was found that tinea capitis was the most prevalent dermatophyte infection found and all patients of tinea capitis were children. Twenty seven dermatophyte strains were isolated, twenty one of them exhibited typical morphology and were fully identified to the species level by using culture-based methods, while the remaining six isolates could not be identified by these conventional methods due to lack of the characteristic morphological features and were identified when submitted to subsequent molecular-based approaches.
The isolated dermatophytes were belonging to four species: 8 strains M. canis (29.6%), 8 strains T. violaceum (29.6%), 6 strains T. rubrum (22.2%) and 5 strains T. mentagrophytes (18.6%) (T. mentagrophytes var. mentagrophytes, 2 strains, and T. mentagrophytes var. interdigitale, 3 strains).
Both PCR approaches identified the typical twenty one isolates to species level with agreement with the diagnosis obtained by using the conventional approach. Furthermore, ITS1/ITS4-based PCR provided no strain differentiation, while (GACA)4-based PCR identified the variants of T. mentagrophytes isolates. For the remaining six atypical dermatophytes, the two molecular PCR-based methods used in this study succeeded to identify them to the species level.
The current study revealed that either ITS or (GACA)4-based PCRs could provide an alternative approach for identification of dermatophytes, especially with the atypical isolates. Moreover, our results suggest that (GACA)4-based PCR has utility as a simple and rapid method for identification of dermatophytes species as well as utility in differentiation of T. mentagrophytes variants.