کتاب Determination of Changing Expression of miR-212 and EGFR Genes

Table of Contents

1-1- Introduction and importance of the subject
Dermatophytosis is one of the most common infections in the world, which is known as Tinea (1, 2). These infections include a wide range of diseases which are highly prevalent but not fatal. Dermatophytosis affects the skin and its appendages (hair and nails), is mainly limited to the keratin layers of the skin and stratum corneum of the epidermis and is caused by various pathological changes in the host as well as because of the presence of fungal agents and their metabolic products. The cell wall of dermatophytes is mainly composed of chitin, glucan and glycopeptides, which are important antigens of the dermatophyte. Trichophytin is indeed an antigenic extract of dermatophytes, especially in Trichophyton species. Most dermatophytes grow best in the presence of one or more amino acids or a number of proteins. Several dermatophytes are autotrophic but certain species are unable to produce certain types of vitamins and are in need of these factors for their growth and development, a feature that is useful for the diagnosis of several types of Trichophyton. These fungi have two stages in their life cycle. Anamorphic or asexual and incomplete stage, namely the stage of fungi when they are isolated in the laboratory and the other stage is teleomorphic (sexual and complete stage), although not all dermatophytes have a sexual stage (3). Dermatophytes cause infections in the skin, hair and nails due to their keratinophilic nature and they include three genera: Microsporum, Epidermophyton and Trichophyton (4).
The sexual stage of Trichophyton and Microsporum is called arthroderma and nannizzia, respectively, but no specific sexual stage has been reported for Epidermophytons. Ecologically, these species are anthropophilic, zoophilic and geophilic, are highly related in terms of physiological and antigenic properties and are able to cause a variety of clinical symptoms in different anatomical sites, includingT. copitis, T. corporis,T. unguium,T. cruris, T. pedis, T. faciei, T. manum and T. barbae (3).
The pathogenesis of Tinea is not fully understood, but a hallmark of dermatophytes is that they have the ability to inhabit the skin and release enzymes that break down the host fat and protein. Specifically, dermatophytes are able to break down creatine and use it to produce nitrogen, which leads to their colonization on the skin and penetration into the host epidermis (5). Dermatophytosis is dependent upon several factors such as migration, environmental conditions, lifestyle, age, the presence of diseases and the immune system (6). Tinea is the only fungal disease that is actually transmissible through the skin and the majority of dermatophytes (80%) do not have a saprophytic form in nature and are completely pathogenic.Nearly 50% of Tinea cases are caused by anthropophilic dermatophytes and the rest by zoophilic and geophilic dermatophytes. Reports of Tinea date back to 14th century and are today of particular importance in both underdeveloped and developed countries (3).
Most studies on dermatophytosis have been conducted in Greece (7-10). In a five-year study (2011-2015) on 2910 patients admitted to teaching hospitals in Greece, out of 2751 patients diagnosed with clinical symptoms of dermatophytes, 294 (10.1%) were infected with dermatophytes through direct microscopic tests (slide preparation) and culture of samples. The highest infection rate was related to Microsporum canis followed by Trichophyton rubrum (35.1%) (11), (Table1-1).

Epidemiological studies show that from 1992 to 2010, T. rubrum had been the most common cause of dermatophytosis (8, 9, 12). Studies in 20 European countries have found that T. pedis(athlete’s foot) and T. unguium are the most prevalent diagnosed fungal infections (13).
However, according to epidemiological studies in several countries, it has been found that T. mentagrophytes is the most common cause of Tinea in Iran(10, 14-19) and that in T. pedis the lowest rate of infection was related to T. mentagrophytes and T. rubrum(8-10, 13, 19). Since our research concerns T. rubrum, we will focus only on this fungus and describe the extent of its involvement, its place in the family of fungi, its morphology and treatment.
The highest infection rate with T. rubrum in Iran is mentioned in winter with low temperature and high humidity, while the season of the year with highest incidence of this fungus has been reported insummer in other countries (20),( Diagram 1-1).

1-2-1- Pathogenesis of Trichophyton rubrum
Given that T. rubrum is an anthropophilic fungus, it is less common in animals (21). However, Van Brozgem believes that an experimental infection by T. rubrum could be developed in guinea pigs, and Rice was able to cause the disease in a rabbit irradiated on the abdomen(3).
Infection with T. rubrum is more common in men than in women. Although infection with the fungus is more prevalent in adults, there have been reports of infection in children as shown in, (Table1-3) (22).
The fungal infection is both acute and chronic and can last for a lifetimein some people. The infection may subside for a while but recur frequently over time. If the antidermatophyte activity of serum is low,the fungus will extensively invade the epithelial cells and dermis (23).
2-2-1- Taxonomy of Trichophyton rubrum
Specific classification of T. rubrum is as follows (24).
– Kingdom: Fungi
– Phylum: Ascomycota
– Subphylum: Pezizomycota
– Class: Eurotiomycotina
– Order: Onygenales
– Family: Arthrodermataceae
– Genus: Trichophyton
– Species: Trichophyton rubrum

Trichophyton megninii, Trichophyton fischeri, Trichophyton raubitschekii, and Trichophyton kanei are other names of this fungus, which was discovered and described by Pehr Henrik Malmsten in 1845 (25-27).
3-2-1- Characteristics of Trichophyton rubrum
If the fungus attacks the hair, the infection is of ectothrix type, is urease negative and does not perforate the hair but absorbs the sorbitol, showing red and light green pigment on Corn meal Agar and Littman Oxgall agar,respectively. T. rubrum lacks fluorescence and its sexual stage is not yet known.
4-2-1- Morphology of Trichophyton rubrum colony
In terms of morphology and appearance of colony, the fungus grows slowly on Sabouraud dextrose agar medium with cyclohexamide, chloramphenicol and gentamicin without pH change and forms white cottony colonies having red underside. If the culture stays longer, it will turn brown. Using a number of compounds, the fungus consumes the glucose of the culture medium, which sometimes produces no red color. The reason for the development of red color is the storage of compounds released during the use of casamino acids erythritol albumin agar (CEA) (21).
5-2-1- Microscopic view of Trichophyton rubrum
In microscopic view, the mycelia are colorless, transparent with transverse walls. The microconidia are teardrop-shaped or nail-shaped, which are scattered around the mycelia. The macroconidia have smooth, thin and parallel walls that are pencil-shaped and long with 2-8 middle blades.Although there a large number of macroconidia in the specimens isolated from inflamed lesions, they are lost during isolation of the fungus. The types isolated from chronic lesions usually lack microconidia or macroconidia. Chlamydoconidia and racquet-shaped hyphae are also seen when the nutrients in medium are decreased (21), (Figure 1-1).