Mycology (I) Lecture Notes PDF

MYCOLOGY (I)  MICOLOGY (I) INTRODUCTION Mycology is the study of fungi. Fungi are eukaryotic organisms that: - do not contain chlorophyll - have cell walls, - filamentous structures, - produce spores. Most...

MYCOLOGY (I)  MICOLOGY (I) INTRODUCTION Mycology is the study of fungi. Fungi are eukaryotic organisms that: - do not contain chlorophyll - have cell walls, - filamentous structures, - produce spores. Most fungi are obligate or facultative aerobes. grow as saprophytes and decompose dead organic matter. There are between 100,000 to 200,000 species depending on how they are classified. About 300 species are presently known to be pathogenic for man.The term mycoses refers to infections that are caused by fungi. There are five kingdoms of living things. The fungi are in the Kingdom Fungi. KINGDOM CHARACTE EXAMPLE RISTIC Monera Prokaryocyte Bacteria Actinomycete s Protista Eukaryocyte Protozoa Fungi Eukaryocyte Fungi Plantae Eukaryocyte Plants Animalia Eukaryocyte Arthropods Mammals Man  MICOLOGY (I) Because fungi (yeasts and molds) are eukaryotic organisms, whereas bacteria are prokaryotic, they differ in several fundamental respects (Table 1). Two fungal cell structures are important medically: 1. The fungal cell wall consists primarily of chitin (not peptidoglycan as in bacteria); thus fungi are insensitive to antibiotics, such as penicillin, that inhibit peptidoglycan synthesis. Chitin is a polysaccharide composed of long chains of N- acetylglucosamine. The fungal cell wall contains other polysaccharides as well, the most important of which is β-glucan, a long polymer of D- glucose. The medical importance of β-glucan is that it is the site of action of the antifungal drug caspofungin.  MICOLOGY (I) (2) The fungal cell membrane contains ergosterol, in contrast to the human cell membrane, which contains cholesterol. The selective action of amphotericin B and azole drugs, such as fluconazole and ketoconazole, on fungi is based on this difference in membrane sterols. There are two types of fungi: yeasts and molds. Yeasts grow as single cells that reproduce by asexual budding. Molds grow as long filaments (hyphae) and form a mat (mycelium). Some hyphae form transverse walls (septate hyphae), whereas others do not (nonseptate hyphae). Nonseptate hyphae are multinucleated (coenocytic). TABLE -1 Comparison of Fungi and Bacteria  MICOLOGY (I) The growth of hyphae occurs by extension of the tip of the hypha, not by cell division all along the filament. Several medically important fungi are thermally dimorphic (i.e., they form different structures at different temperatures). They exist as molds in the environment at ambient temperature and as yeasts (or other structures) in human tissues at body temperature. Most fungi are obligate aerobes; some are facultative anaerobes; but none are obligate anaerobes. All fungi require a preformed organic source of carbon, hence their frequent association with decaying matter.  MICOLOGY (I) The natural habitat of most fungi is, therefore, the environment. An important exception is Candida albicans, which is part of the normal human flora. Some fungi reproduce sexually by mating and forming sexual spores (e.g., zygospores, ascospores, and basidiospores). Zygospores are single large spores with thick walls; ascospores are formed in a sac called ascus; and basidiospores are formed externally on the tip of a pedestal called a basidium. The classification of these fungi is based on their sexual spores. Fungi that do not form sexual spores are termed “imperfect” and are classified as fungi imperfecti..  MICOLOGY (I) Most fungi of medical interest propagate asexually by forming conidia (asexual spores) from the sides or ends of specialized structures (Figure -1). The shape, color, and arrangement of conidia aid in the identification of fungi. Some important conidia are 1. arthrospores, which arise by fragmentation of the ends of hyphae and are the mode of transmission of Coccidioides immitis; 2. chlamydospores, which are rounded, thick-walled, and quite resistant (the terminal chlamydospores of C. albicans aid in its identification);  MICOLOGY (I) 3. blastospores, which are formed by the budding process by which yeasts reproduce asexually (some yeasts, e.g., C. albicans, can form multiple buds that do not detach, thus producing sausagelike chains called pseudohyphae, which can be used for identification); and 4. sporangiospores, which are formed within a sac (sporangium) on a stalk by molds such as Rhizopus and Mucor.  MICOLOGY (I) Although this course focuses on the fungi that are human pathogens, it should be remembered that fungi are used in the production of important foods (e.g., bread, cheese, wine, and beer). Fungi are also responsible for the spoilage of certain foods. Because molds can grow in a drier, more acidic, and higher osmotic pressure environment than bacteria, they tend to be involved in the spoilage of fruits, grains, vegetables, and jams. FIGURE -1 Asexual spores. A: Blastoconidia and pseudohyphae (Candida). B: Chlamydospores (Candida). C: Arthrospores (Coccidioides). D: Sporangia and sporangiospores (Mucor). E: Microconidia (Aspergillus). F: Microconidia and macroconidia (Microsporum).  MICOLOGY (I) PATHOGENESIS The response to infection with many fungi is the formation of granulomas. Granulomas are produced in the major systemic fungal diseases (e.g., coccidioidomycosis, histoplasmosis, and blastomycosis, as well as several others). The cell- mediated immune response is involved in granuloma formation. Acute suppuration, characterized by the presence of neutrophils in the exudate, also occurs in certain fungal diseases such as aspergillosis and sporotrichosis. Fungi do not have endotoxin in their cell walls and do not produce bacterial-type exotoxins.  MICOLOGY (I) Activation of the cell-mediated immune system results in a delayed hypersensitivity skin test response to certain fungal antigens injected intradermally. A positive skin test indicates exposure to the fungal antigen. It does not imply current infection, because the exposure may have occurred in the past. A negative skin test makes the diagnosis unlikely unless the patient is immunocompromised. Because most people carry Candida as part of the normal flora, skin testing with Candida antigens can be used to determine whether cell-mediated immunity is normal. The transmission and geographic locations of some important fungi are described in Table -2. TABLE -2 Transmission and Geographic Location of Some Important Fungi  MICOLOGY (I) Intact skin is an effective host defense against certain fungi (e.g., Candida, dermatophytes), but if the skin is damaged, organisms can become established. Fatty acids in the skin inhibit dermatophyte growth, and hormone-associated skin changes at puberty limit ringworm of the scalp caused by Trichophyton. The normal flora of the skin and mucous membranes suppress fungi. When the normal flora is inhibited (e.g., by antibiotics), overgrowth of fungi such as C. albicans can occur.  MICOLOGY (I) In the respiratory tract, the important host defenses are the mucous membranes of the nasopharynx, which trap inhaled fungal spores, and alveolar macrophages. Circulating IgG and IgM are produced in response to fungal infection, but their role in protection from disease is uncertain. The cell-mediated immune response is protective; its suppression can lead to reactivation and dissemination of asymptomatic fungal infections and to disease caused by opportunistic fungi.  MICOLOGY (I) FUNGAL TOXINS & ALLERGIES In addition to mycotic infections, there are two other kinds of fungal disease: 1.Mycotoxicoses, caused by ingested toxins. 2.Allergies to fungal spores. The best-known mycotoxicosis occurs after eating Amanita mushrooms. These fungi produce five toxins, two of which amanitin and phalloidin are among the most potent hepatotoxins. The toxicity of amanitin is based on its ability to inhibit cellular RNA polymerase, which prevents mRNA synthesis.  MICOLOGY (I) Another mycotoxicosis, ergotism, is caused by the mold Claviceps purpurea, which infects grains and produces alkaloids (e.g., ergotamine and lysergic acid diethylamide [LSD]) that cause pronounced vascular and neurologic effects. Other ingested toxins, aflatoxins, are coumarin derivatives produced by Aspergillus flavus that cause liver damage and tumors in animals and are suspected of causing hepatic carcinoma in humans. Aflatoxins are ingested with spoiled grains and peanuts and are metabolized by the liver to the epoxide, a potent carcinogen.  MICOLOGY (I) Allergies to fungal spores, particularly those of Aspergillus, are manifested primarily by an asthmatic reaction (rapid bronchoconstriction mediated by IgE), eosinophilia, and a “wheal and flare” skin test reaction. These clinical findings are caused by an immediate hypersensitivity response to the fungal spores. MICOLOGY (I)  MICOLOGY (I) The term mycoses refers to infections that are caused by fungi. Medically important fungi are in four: 1. Ascomycota - Sexual reproduction in a sack called an ascus with the production of ascopspores. 2. Basidiomycota -Sexual reproduction in a sack called a basidium with the production of basidiospores. 3. Zygomycota - sexual reproduction by gametes and asexual reproduction with the formation of zygospores. 4. Mitosporic Fungi (Fungi Imperfecti) - no recognizable form of sexual reproduction. Includes most pathogenic fungi.  MICOLOGY (I) The mycoses with the highest incidence candidiasis and dermatophytosis are caused by fungi that are frequent components of the normal human microbiota and highly adapted to survival on the human host. Fungi were initially classified into phyla based largely on their modes of sexual reproduction and phenotypic data. Most pathogenic yeasts (Saccharomyces, Candida) and molds (Coccidioides, Blastomyces, Trichophyton) are ascomycetes. The basidiomycetes include mushrooms as well as pathogenic species of Cryptococcus.  MICOLOGY (I) The two largest phyla, Ascomycota and Basidiomycota, are well supported by phylogenetic analyses. These phyla contain yeasts, molds, and dimorphic species. The Phylum Ascomycota (or ascomycetes) includes more than 60% of the known fungi and about 85% of the human pathogens. Most of the other pathogenic fungi are members of the Phylum Basidiomycota (basidiomycetes) or the Order Mucorales. The Major Mycoses and Causative Fungi  MICOLOGY (I) CLASSIFICATION OF FUNGI The fungi are classified on the basis of their mode of sexual reproduction; Most fungi reproduce by forming conidia through mitosis (asexual reproduction), during which the chromosome number remains the same.  MICOLOGY (I) MORPHOLOGY Pathogenic fungi can exist as: 1. Yeasts: are unicellular organisms. reproduce by budding. 2. Hyphae: mass of hyphae is called mycelia are multicellular filamentous structures. constituted by tubular cells with cell walls. The mycelial forms branch and the pattern of branching is an aid to the morphological identification. If the mycelia do not have SEPTA, they are called coenocytic (nonseptate). The terms "hypha" and "mycelium" are frequently used interchangeably. 3. Dimorphic fungi occur in both the yeast and mycelial forms.  MICOLOGY (I) The dimorphic fungi have two forms (figure 1): 1. YEAST - (parasitic or pathogenic form). - This is the form usually seen in tissue, in exudates, or if cultured in an incubator at 37ºC. 2. MYCELIUM - (saprophytic form). - The form observed in nature or when cultured at 25ºC. - Conversion to the yeast form appears to be essential for pathogenicity. Candida albicans is a dimorphic fungus in that it grows as a unicellular yeast under some environmental conditions and as a filamentous fungus under other conditions. Budding yeast cells. C. albicans was grown at 37°C with aeration for 3 h in yeast-peptone-dextrose (YPD) medium. In this image, unstained cells are magnified x400. The image was taken with phase- contrast microscopy. Budding yeast with septum. The septum has formed between the daughter bud and the mother cell, but separation of the two has not occurred. This image is from a culture of cells grown at 37° C for 3 h in YPD medium. The unstained cell is magnified x1,000 using phase- contrast microscopy Candida albicans mother and daughter cells. Cells were grown under conditions that induced hypha formation for 30 min. The daughter cell is on the right; the mother cell is on the left. The daughter cell has not reached a threshold volume and therefore has not yet formed a hypha. The mother cell has passed the threshold volume and has started forming a germ tube which will become a hypha. The germ tube seen here is 6 min old. A septum between the germ tube and the mother cell has not yet formed. The unstained cells are magnified x1,000 using phase-contrast C. albicans cell at 3 h. Three hours after the appearance of the germ tube, the hypha has septa. A new germ tube at the distal pole of the cell is also evident at this time. The unstained cells are magnified x1,000 using phase-contrast microscopy. C. albicans hyphal cells at 5 h. After 5 h in hypha-inducing medium, many hyphae are evident. Clumping of the hyphae is also apparent, and hyphae are beginning to form hypha blastospores, which are new budding cells.  MICOLOGY (I) GROWTH & ISOLATION OF FUNGI Most fungi occur in nature and grow readily on simple sources of nitrogen and carbohydrate. Sabouraud's agar (Traditional media),, which contains glucose and beef extract (pH 5.0), has been used because it does not readily support the growth of bacteria.  MICOLOGY (I) DIAGNOSIS 1. Skin scrapings Suspected to contain dermatophytes or pus from a lesion can be examined directly under the microscope. 2. Skin testing (dermal hypersensitivity) Used to be popular as a diagnostic tool. 3. Serology May be helpful when it is applied to a specific fungal disease. Because fungi are poor antigens, the efficacy of serology varies with different fungal infections. The most common serological tests for fungi are based on - latex agglutination (favor the detection of IgM). - double immunodiffusion (usually detect IgG) - complement fixation - enzyme immunoassays (Some EIA tests are being developed to detect both IgG and IgM antibodies). - There are some tests which can detect specific fungal antigens, but they are just coming into general use.  MICOLOGY (I) 4. Direct fluorescent microscopy 5. Biopsy and histopathology. A biopsy may be very useful for the identification and as a source of the of tissue-invading fungi. Usually the Gomori methenamine silver (GMS) stain is used to reveal the organisms which stain black against a green background 6. Culture. A definitive diagnosis requires a culture and identification. Pathogenic fungi are usually grown on Sabouraud dextrose agar. It has a slightly acidic pH (~5.6). cyclohexamide, penicillin, streptomycin or other inhibitory antibiotics are often added to prevent bacterial contamination and overgrowth. Two cultures are inoculated and incubated separately at 25 degrees C and 37 degrees C to reveal dimorphism. The cultures are examined macroscopically and microscopically. They are not considered negative for growth until after 4 weeks of incubation. Mycology- Defifinitions SKIN - ANATOMY HAIR - DIAGRAM NAIL- DIAGRAM  MICOLOGY (I) CLINICAL CLASSIFICATION OF THE MYCOSES (Table 5.1) a. Superficial mycoses b. Cutaneous c. Subcutaneous mycoses d. Systemic mycoses e. Opportunistic mycoses  MICOLOGY (I) (Table 5.1) Type of Infection Causative Organism Disease Superficial Malassezia furfur Pityriasis versicolor Cutaneous Trichophyton, Epidemophyton, Dermatophytosis (ringworm of skin, scalp, nails). and Microsporum species Candida albicans Candidiasis of skin, oral candidiasis (thrush) of mucous membranes Subcutaneous Sporothrix schenkii Sporotrichosis Deep Blastomyces dermatitidis Blastomycosis Coccoidioides immitis Coccidioidomycosis Histoplasma capsulatum Histoplasmosis Paracoccidioides brasiliensis Paracoccidioidotnycosis Deep opportunistic Aspergillus fumigatus and other Aspergillosis Aspergillus species Candida albicans and other Candidia Candida species Cryptococcus neoforrnans Cryptococcosis Mucor and Rhizopus species Zygomycosis  MICOLOGY (I) The Superficial mycoses - Are fungal diseases that are confined to the outer layers of the skin, nail, or hair, (keratinized layers) rarely invading the deeper tissue or viscera. Cutaneous - The fungi involved are called dermatophytes. The Subcutaneous mycoses - Are confined to the subcutaneous tissue and only rarely spread systemically. - They usually form deep, ulcerated skin lesions or fungating masses, most commonly involving the lower extremities. - The causative organisms are soil saprophytes which are introduced through trauma to the feet or legs. The Systemic mycoses - may involve deep viscera and become widely disseminated. The Opportunistic mycoses - Are infections due to fungi with low inherent virulence. - The aetiologic agents are organisms which are common in all environments.  MICOLOGY (I) A. SUPERFICIAL MYCOSES 1. TINEA VERSICOLOR (Pityriasis Versicolor) Tinea versicolor is a common mild superficial infection that appears to be the result of overgrowth of Malassezia furfur (member of the normal skin flora). Growth within the skin (stratum corneum) of clusters of spherical, thick-walled budding cells and short, bent hyphae of Malassezia furfur usually causes no pathologic signs other than fine to brawny scales. Tinea Versicolor Tinea Versicolor  MICOLOGY (I) Clinical picture: - The lesions range from depigmented to brownish-red and are of only cosmetic importance. - It is commonly on the chest, back, abdomen, neck, and upper arms.  MICOLOGY (I) 2. TINEA NIGRA Light brown to blackish macular areas appear most commonly on the palmar or plantar stratum corneum. These are filled with brownish, branched, septate hyphae and budding cells of Exophiala werneckii. No scaling or other reaction develops. Typical brown to black, non-scaling macules on the palmar aspect of the hands.  MICOLOGY (I) 3. PIEDRA Hard black nodules (black piedra) are formed around the scalp hair by Piedraia hortae. Softer, white to light brown nodules (white piedra) caused by Trichosporon beigelii form on axillary, pubic, beard, and scalp hair. Relapse is common.. Superficial mycoses - infections limited to the outermost layers of the skin and hair Identification of Disease Etiological Agent Symptoms organism "spaghetti and meatballs" Pityriasis hypopigmented Malassezia furfur appearance of versicolor macules organism in skin scrapings black, 2-celled oval Tinea nigra Exophiala werneckii black macules yeast in skin scrapings black nodule on hair black nodule on hair shaft composed of Black piedra Piedraia hortai shaft spore sacs and spores white nodule on hair creme-colored shaft composed of White piedra Trichosporum beigelii nodules on hair shaft mycelia that fragment into arthrospores  MICOLOGY (I) CUTANEOUS MYCOSES The cutaneous mycoses are caused by fungi that invade only superficial keratinized tissue (skin, hair, and nails) and not the deeper tissues. The most important of these are the dermatophytes, a group of closely related fungi classified into three genera: - Epidermophyton. - Microsporurn. - Trichophyton.  MICOLOGY (I) In culture, they develop characteristic colonies by means of which they can be divided into species. Some species are found only in soil and never produce infection. Other soil species may produce disease in humans. Others have evolved to complete parasitism, are communicable, and are not found in soil. Most dermatophytes are worldwide in distribution  MICOLOGY (I) Table 5.2 Some Clinical Features of Dermatophyte Infection  MICOLOGY (I) Diagnostic Laboratory Tests Specimens: - Specimens consist of scrapings from both the skin and the nails plus hairs plucked from involved areas. - Microsporum-infected hairs fluoresce under Wood's light in a darkened room. Microscopic Examination: - Specimens are placed on a slide in a drop of 10-20% potassium hydroxide and examined. - In skin or nails, branching hyphae or chains of arthrospores are seen. - In hairs, Microsporum species form dense sheaths of spores in a mosaic pattern around the hair; - Trichophyton species form parallel rows of spores outside (ectothrix) or inside (endothrix) the hair shaft.  MICOLOGY (I) Culture: - All final identification of dermatophytes rests on cultures. - Specimens are inoculated onto Sabouraud's agar slants containing cycloheximide and chloramphenicol to suppress mold and bacterial growth. - incubated for 1-3 weeks at room temperature, and further examined in slide cultures if necessary. - Species determination is made on the basis of colonial morphology, microscopic examination, and in some cases biochemical tests.  MICOLOGY (I) Figure 5.12  MICOLOGY (I) Epidemiology & Control Infection arises from contact of uninfected skin or hair with infected skin scales or hair stubs. Hyphae then grow into the stratum corneum. Sporadic cases of ringworm infection are acquired from cats or dogs (M cams). Epidemics of tinea capitis have been traced to the use of shared barbershop clippers, transfer of infected hairs on headrests in common carriers, and person-to-person contact. Control depends on - cleanliness, sterilization of instruments. - effective treatment of cases. - reduced contact with infectious materials.  MICOLOGY (I) Athlete's foot is found only in people who wear shoes. Infection spreads through the use of common showers and dressing rooms, where infected desquamated skin serves as a source of infection. No really effective control measures are available other than proper hygiene and the use of talc to keep interdigital spaces dry. In many persons, chronic athlete's foot is asymptomatic and becomes activated only in excessive heat or moisture or with unsuitable footwear. Open-toed shoes or sandals are best for general wear. Athlete's foot  Cutaneous mycoses - infections that extend deeper into the epidermis, as well as invasive hair and nail diseases Indentification of Disease Etiological Agent Symptoms organism presence/absence and shape of Microsporum sp. Trichophyton Tinea capitis ringworm lesion of scalp micro- and macroconidia in sp. Epidermophyton sp. scrapings from lesion presence/absence and shape of Microsporum sp. Trichophyton ringworm lesion of trunk, arms, Tinea corporis micro- and macroconidia in sp. Epidermophyton sp legs scrapings from lesion presence/absence and shape of Microsporum sp. Trichophyton Tinea manus ringworm lesion of hand micro- and macroconidia in sp. Epidermophyton sp scrapings from lesion presence/absence and shape of Microsporum sp. Trichophyton Tinea cruris "jock itch" ringworm lesion of groin micro- and macroconidia in sp. Epidermophyton sp scrapings from lesion presence/absence and shape of Tinea pedis"athlete's Microsporum sp. Trichophyton ringworm lesion of foot micro- and macroconidia in foot" sp. Epidermophyton sp scrapings from lesion presence/absence and shape of Microsporum sp. Trichophyton Tinea unguium infection of nails micro- and macroconidia in sp. Epidermophyton sp scrapings from lesion Microsporum sp. Trichophyton mycelium and spores on hair Ectothrix infection of hair shaft surface sp. Epidermophyton sp shaft Microsporum sp. Trichophyton mycelium and spores in hair Endothrix infection of hair shaft interior sp. Epidermophyton sp shaft  MICOLOGY (I) B. SUBCUTANEOUS MYCOSES The fungi that cause subcutaneous mycoses grow in soil or on decaying vegetation. They must be introduced into subcutaneous tissue in order to produce disease. In general, lesions spread slowly from the area of implantation. Extension via lymphatics draining the lesion is slow except in sporotrichosis.  MICOLOGY (I) 1. SPOROTHRIX SCHENCKII Sporothrix schenckii is a dimorphic fungus that lives on plants or wood and causes sporotrichosis, a chronic granulomntous infection, when( traumatically,, introduced into the skin). There is often a characteristic spread along lymphatics draining the area.  MICOLOGY (I) The organisms are rarely seen in pus and tissues from human infections They may appear as small, round to cigar-shaped. In cultures at room temperature on Sabouraud's agar, cream-colored to black, folded, leathery colonies develop within 3-5 days. Heat-killed saline suspensions of cultures (or carbohydrate fractions from them) give positive delayed skin tests in infected humans or animals. A variety of antibodies are found in infected patients and some-times also in normal individuals.  MICOLOGY (I) The fungus is introduced into the skin by trauma. A local lesion develops as a pustule, abscess, or ulcer, and the lymphatics leading from it become thickened and cord-like. Multiple sub-cutaneous nodules and abscesses occur along the lymphatics. Usually there is little systemic illness associated with these lesions. S. schenckii occurs worldwide in nature on plants.  MICOLOGY (I) Diagnostic Laboratory Tests.Specimens: Specimens consist of pus or biopsy from lesions. Microscopic Examination: - In human lesions, organisms are seen infrequently. - In mice lesions, budding cells are abundant Culture: - On Sabouraud's agar, typical colonies with clusters of conidia are diagnostic. - They should convert to yeast morphology during incubation at 37 °C. Serology - Agglutination of yeast cell suspensions or of latex particles coated with antigen occurs in high titer with sera of infected patients but is not diagnostic.  MICOLOGY (I) 2. CHROMOBLASTOMYCOSIS (Chromomycosis) Chromoblastomycosis is a slowly progressive granulomatous infection of skin caused by several species of black molds: - Phialophora verrucosa. - Fonsecaea pedrosoi. - Rhinocladiella aquaspersa. - Cladosporiurn carrionii In exudates and tissues, these fungi produce dark brown, thick-walled, rounded cells.  MICOLOGY (I) The fungi are introduced by trauma into the skin, often on the legs or feet. Slowly over months, or years; wart-like growths extend along the lymphatics of the affected area. Cauliflower-like nodules with crusting abscesses eventually cover the area.  MICOLOGY (I) Diagnostic Laboratory Tests Specimens: Specimens consist of scrapings or biopsy from lesions. Microscopic Examination: - Detection of the sclerotic bodies is diagnostic. - Tissue sections show granulomas and organisms. Culture: - Specimens should be cultured on Sabouraud's agar.  MICOLOGY (I) Chromoblastomycosis occurs mainly in the tropics. The fungi are saprophytic in nature, probably occurring on vegetation and in soil. The disease occurs chiefly on the legs of barefoot farm workers, presumably following traumatic introduction of the fungus. The disease is not communicable. Wearing shoes and protecting the legs probably would prevent infection.  MICOLOGY (I) 3. MYCETOMA Mycetoma is a localized, swollen lesion with granules that are compact colonies of the causative agent draining from sinuses. It is caused by a variety of fungi and aerobic actinomycetes (filamentous bacteria). The term actinomycetoma is used to distinguish those cases caused by actinomycetes. Mycetoma develops when these soil organisms are implanted by trauma into subcutaneous tissue. The term maduromycosis or Madura foot is often used to denote those infections caused by fungi, but the clinical disease resembles actinomycetoma, though therapy is different.  MICOLOGY (I) Mycetomas are rarely seen outside of the tropics and are particularly prevalent in India, Africa, and Latin America. White, yellow, red, or black granules are extruded in pus. The granules due to fungi consist of inter- twined, septate hyphae. They may have larger, thick-walled cells at the periphery. The actinomycete granule consists only of filamentous hyphae  MICOLOGY (I) After one of the causative microorganisms has been introduced into the subcutaneous tissue (usually the foot, hand, or back) by trauma, abscesses form that may extend through muscle and even into bone, eventually draining through chronic sinuses. The organism can be seen as a compact granule in the pus. Untreated lesions persist for years and extend deeper and peripherally, causing deformity and loss of function.  MICOLOGY (I) The organisms producing mycetoma occur in soil and on vegetation. Barefoot farm laborers are therefore commonly exposed. Properly cleaning wounds and wearing shoes are reasonable control measures. There is no established therapy for fungal mycetoma, though prolonged treatment with oral ketoconazole or itraconazole may be beneficial. Surgical excision of early lesions may prevent spread. 4. PHAEOHYPHOMYCOSIS  Subcutaneous mycoses - infections involving the dermis, subcutaneous tissues, muscle and fascia Identification of Disease Etiological Agent Symptoms Organism Budding yeast in tissue Nodules and ulcers exudate that converts to Sporotrichosis Sporothrix schenckii along lymphatics at site mold with "rosette of inoculation pattern" of conidiation on culture at 25oC. Fonsecaea pedrosoi Warty nodules that Copper-colored Fonsecaea compacta progress to "cauliflower- spherical yeast called Chromoblastomycosis like" appearance at site "Medlar bodies" in Wangiella dermatitidis of inoculation tissue Pseudallescheria boydii White, brown, yellow or Madurella grisea Draining sinus tracts at black granules in Mycetoma site of inoculation exudate that are fungal Madurella mycetomatis colonies Genus:Epidermophyton -Species: floccosum- Disease(s):Tinea-Image Type:Microscopic Morphology Genus:Malassezia -Species: furfur- Disease(s):Fungemia Tinea Versicolor Image Type:Microscopic Morphology-Title:Growth on medium overlaid with olive oil Trichophyton mentagrophytes contracted from a dog Ringworm, stained preparation, macroconidia of Microsporum canis Ringworm caused by Microsporum gypseum, culture plate with Sabouraud's dextrose agar Onychomycosis due to Trychophyton rubrum, right and left great toe. Tinea unguium. Sulphur granules in actinomycosis Black grain mycetoma: subcutaneous nodule due to Madurella Mycetomatis, magnified x 100 Genus:Microsporum Species: canis Disease(s):Tinea Title:Ringworm lesions Image: Ringworm lesions developed after an exposure to a cat having ringworm. Genus: Microsporum Species: audouinii Disease(s): Tinea capitis Image Type: Clinical Presentation Title: Tinea capitis Image Legend: Lesions on the scalp. Genus:Microsporum Species: audouinii Disease(s): Tinea capitis Image Type: Microscopic Morphology Title: Macroconidium Image Legend: Rough-walled macroconidium. Differential interference contrast microscopy, 630X. Genus:Epidermophyton Species: floccosum Disease(s):Tinea corporis Image Type:Clinical Presentation Image Legend:Submammary tinea corporis caused by E. floccosum. Genus: Microsporum Species: canis Disease(s): Tinea corporis Image Type: Clinical Presentation Title: Ringworm Image Legend: Circular lesion with raised border. The fungus came from a pet cat. Genus: Microsporum Species: canis Disease(s): Tinea corporis Image Type: Clinical Presentation Reference #: GK 172 Image Legend: Young boy showing numerous, circular scaling lesions with distinct erythematous borders following contact with kittens. M. canis was isolated.  Genus:Microsporum Species: canis Disease(s):Tinea corporis Young girl showing M. canis lesions in chickenpox scars following contact with family cat. Genus: Epidermophyton Species: floccosum Disease(s): Tinea cruris Image Type: Clinical Presentation Image Legend: Tinea of the groin (tinea cruris) showing typical circular, erythematous lesions with raised advancing margins. Genus: Epidermophyton Species: floccosum Disease(s): Tinea cruris Image Type:Microscopic Morphology Title: Clavate conidia Image Legend: Clavate conidia smooth-walled conidia and thick- walled chlamydoconidia. Phase contrast microscopy, 630X. Genus: Epidermophyton Species: floccosum Disease(s):Tinea pedis Image Type: Clinical Presentation Image Legend: Severe tinea of the foot (tinea pedis) caused by E. floccosum showing extensive scaling. Genus:Scytalidium Species: dimidiatum Disease(s): Dermatomycosis Tinea pedis Image Type: Histopathology Title: Hyphae in tissue Image Legend: Microscopic view of fungal element in skin. KOH preparation.  Trichophyton mentagrophytes Genus/Species: Trichophyton mentagrophytes Title: Tinea Image Type: Clinical Presentation pedis Disease(s): Tinea pedis Legend: Infection involving the toes and interdigital spaces.