MYCOLOGY Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicine, food, and entheogens, as well as their dangers, such as poisoning or infection. A biologist specializing in mycology is called a mycologist

FUNGI

Classification of fungi Group Representative Genera Phylum Zygomycota Rhizopus, Absidia, Mucor Phylum Dikaryomycota •Subphylum Ascomycotina Trichophyton, Histoplasma, Blastomyces •Subphylum Basidiomycotina Cryptococcus Deuteromycotina Candida, Epidermophyton, Coccidioides

EXAMPLES: - Cryptococcus neoformans - YEAST - Candida albicans Fungi (yeast& molds) are eukaryotic organisms whereas bacteria are prokaryotic, they differ regarding;

Size-diameter 4 um-------1um Nucleus. Cytoplasm Cell membrane, Sterol---absent in bacteria Cell wall, Chitin ----peptidoglycan Thermal dimorphism. Metabolism.

BACTERIA CELL

Fungal cell wall Consists of chitin not peptidoglycan like bacteria. Thus fungi are insensitive to antibiotics as penicillin.

FUNGAL CELL

Chitin is a polysaccharide composed of long chain of n-acetyleglucasamine. Also the fungal cell wall contain other polysaccharide, B-glucan, which is the site of action of some antifungal drugs.

Fungal cell membrane Consist of ergosterol rather than cholesterol like bacterial cell membrane. Ergosterol is the site of action of antifungal drugs, amphotericin B & azole group

Atmospheric & carbon source requirements Most fungi are obligatory aerobes, some are facultative anaerobes, but none are obligatory anaerobes All fungi require a performed organic source of carbon –association with decaying matter.

Natural habitat The environment. Exception Candida albicans is part of normal human flora.

Life cycle - sexual reproduction & - assexual reproduction

Morphology of Fungi Yeasts Yeast-like fungi Dimorphic fungi Filamentous fungi (molds) Yeasts Yeast-like fungi Dimorphic fungi

Filamentous Fungi 1.The basic morphological elements of filamentous fungi are long branching filaments or hyphae, which intertwine to produce a mass of filaments or mycelium 2.Colonies are strongly adherent to the medium and unlike most bacterial colonies cannot be emulsified in water.

mycelium: septate mycelium: non septate

Mycelia & Conidia

3. The surface of these colonies may be velvety, powdery, or may show a cottony aerial mycelium. 4. Pigmentation of the colony itself and of the underlying medium is frequently present.

Medical mycology Is the study of mycoses of man and their etiologic agents. Mycoses Are the diseases caused by fungi. Of the several thousands of species of fungi that are known, less than 100 are pathogenic to man.

Predisposing factors: 1. A debilitating condition of the host, as Diabetes. 2. A concurrent disease such as leukaemia. 3. Prolonged treatment with corticosteroids. 4.Immunosuppressive drugs or an antibiotic for long duration.

1. Yeast These occur in the form of round or oval bodies which reproduce by the formation of buds known as blastospores. Yeasts colonies resemble bacterial colonies in appearance and in consistency. The only pathogenic yeast in medical mycology is Cryptococcus neoformans.

Yeast colonies - Cryptococcus Mucoid colonies

Cryptococcus neoformans SEM Capsule

Candida Colonies Candida albicans

Candida albicans SEM

Thermally Dimorphic Fungi These are fungi which exhibit a filamentous mycelial morphology (saprophytic phase) when grown at room temperature 27oC, but have a typical yeast morphology (parasitic phase) inside the body and when grown at 37oC in the laboratory (e.g. Histoplasmosis).

Histoplasma capsulatum 27⁰C

Histoplasma capsulatum 37oc

Human fungal infection; MAY BE: Superficial Subcutaneous Systemic Opportunistic

Superficial mycoses

Subcutaneous mycoses Chromomycosis Mycetoma Sporotrichosis

Systemic Mycoses

Systemic Mycoses H/W: WHAT IS VAGINAL CANDIDIOSIS?? -infection of female genitals by yeast-like fungus causing whitish patches. Systemic Mycoses

Fungi infections Classified according to the site infected or the immune status of the host; Superficial mycosis: outermost layers of skin, hair and nails. Cutaneous mycosis: involve the keratin – containing epidermis and deeper layers of the hair, skin and nails. Subcutaneous mycosis: involve the dermis, subcutaneous tissue, muscles, and fascia Systemic mycosis: often originate from lungs but disseminate to other organs ( especially in immunocompromised individuals) Opportunistic mycosis: occur only in patients with compromised immune system (e.g cancer patient receiving immunosuppressive therapy, HIV infected individuals)

Diagnosis Fungi infections mimic other diseases therefore be care: a) Isolation of fungi from specimen may require culturing for up to 30 days at 25⁰C and 35 ⁰C on appropriate media (antimicrobial antibiotic should be included in the media to inhibit bacterial growth) b) Specific histologic stain: can be used for direct visualization of fungi in tissue specimen. skin scrapings are treated with 10% - 15% KOH to destroy tissue element.

Diagnosis conti… C) sugar utilization test: (somehow similar to the fermentation test of Enterobacteriaceae) are useful in identifying yeast. 2. Detection of fungal antigens in blood or cerebrospinal fluid (CSF). Is done by ELISA

  SUPERFICIAL MYCOSES   The superficial (cutaneous) mycoses are confined to the outer layers of skin, hair, and nails They produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin a) Pityriasis verscolor and pityriasis nigra involve the outer layer of the skin Treated with Keratin-removing agents or with topical miconazole b) White piedra and black piedra involve the hair shaft, treated by cutting hair below the nodular lesions.

CLINICAL MANIFESTATIONS Tinea means "ringworm" or "moth-like". the term refer to a variety of lesions of the skin or scalp. Tinea corporis - small lesions occurring anywhere on the body . may be produced by any of the species of the dermatophytes.

Cutaneous mycoses Trichophyton rubrum and T. mentagrophytes are the most common Invasion of the horn layer of the skin is followed by spread of the organism causing characteristic rings of inflammation They may elicit cellular immune response, leading to inflamed , outward spreading lesions. They may contribute to seborrhea and dandruff.

Clinical manifestations 1. Ringworm: the common name of the infection which describe the lesions, which are in form of ring and resemble a worm burrowing the skin. Tinea plus indicate the site infected eg Tinea capitis - head. Frequently found in children. can appear as non inflamed scaly red lesion or with loss of hair(alopecia) on the scalp, eye brows, and eye lids. Infection occurs as an expanding rings on the scalp with organism growing in and on the hair Inflammatory reaction may cause deep ulcers which heal with scarring and permanent loss of hair.

Tina pedis or athletic feet. Major cause Trichophyton rubrum and T. mentogrophytes. Because the infection appear to require warmth and moisture to progress the infection is usually found in those who wear shoes

The infection begins between the toes and symptoms may vary from a chronic disease with peeling and cracking of the skin to an acute ulcerative form of infection. It is thought initial contact with the organisms probably occurs in places like common shower stalls and bathing facilities

Tinea cruris - "jock itch" Tinea cruris - "jock itch". Infection of the groin, perineum or perianal area. Tinea barbae - ringworm of the bearded areas of the face and neck Tinea versicolor - Characterized by a blotchy discoloration of skin which may itch. Tinea unguium ring worm of the nails Tinea manuum ring worm of the hand

ETIOLOGIC AGENTS There are three genera of superficial mycoses (dermatophytes): 1. Trichophyton species These infect skin, hair and nails. Rarely can cause subcutaneous infections, in immunocompromised individuals. 2. Microsporum species. These may infect skin and hair, rarely nails. 3. Epidermophyton   These infect skin and nails and rarely hair.

Clinically: Laboratory: DIAGNOSIS Clinically: For the dermatophytes, appearance of the lesions is usually diagnostic. Laboratory: Skin scrapings with 10% potassium hydroxide can reveal hyphae or spores. Most fungi can be grown on Sabouraud's dextrose agar but they are often very difficult to speciate.

Treatment a (Skin infections) use of azole antifungal such as ketoconazole, miconazole or clotrimazole b) Hair infections: ketoconazole or sulfur containing shampoos, griseofulvin c) Nails: azole antibiotics, (topical or systemic) surgical or removal of the infected nail.

They gain entrance to the body as a result of trauma to the skin. Subcutaneous Mycosis Infection is caused by melanin –containing (dematenaceous) fungi present in the soil or decaying vegetation. They gain entrance to the body as a result of trauma to the skin. Once established they remain localized in the traumatized area but may extend by the way of draining lymph channels to regional lymph nodes. Fungi involved in subcutaneous type of mycosis are normal soil inhabitants

Sporothrix schenkii Sporothrix schenkii - etiologic agent of sporotrichosis is found in soil and plants world wide but sporadic distribution It also occur in wood and moss infections result from inoculation by splinters thorn pricks, sphagnam moss grass or garden soil Thus infection is an occupational hazard for gardener and green house workers

Epidemiology and pathogenesis Sporotrichcosis is a localized infection of the skin subcutaneous tissue and regional lymphatic that gain entrance to the body following trauma or through open wounds After an incubation period varying from one week to six month a subcutaneous nodule appears and develops into a necrotic ulcer. The initial lesions heal as a new ulcer appear in adjacent areas Lymphatic in the area develop nodules and ulcers along the lymph channels and these may persist for months or years

Diagnosis and treatment Sporothrix schenckii grows in culture Rarely invade the blood and spread to various organs of the body Occasionally the fungi can enter the host by way of respiratory tract resulting in a primary pulmonary sporotrichosis Because of the wide spread occurrence of S. schenckii, protective clothing especially gloves should be worn when handling potentially infectious materials Diagnosis and treatment Sporothrix schenckii grows in culture

Treatment Oral potassium iodide administered over a period of weeks is the most common treatment for localized Sporotrichosis how ever amphoteric B is used for relapsing cases as well as for pulmonary and disseminated Sorotrichosis

Chromomycosis Epidemiology and pathogenesis The causative agents are soil saprophytes found in decaying vegetative matter and rotting wood most infection appear to have originated from puncture wounds Majority of this occurs in the tropics and most infection occur on the legs and feet in rural areas where shoes are rarely worn The original lesion appear as small raised violet papule and over a period of months to years additional lesions appear in adjacent area

The lesions are hard, dry and usually raised 1 to 3 mm above the skin surface clusters of such growths resemble floret of cauliflower The infection remains localized without involving borne or muscle or even causing particular discomfort to the patient

Lesions may become secondary infected with bacteria Rarely spreading may occur by way of blood stream to involve other areas of the body as lungs and brain occasionally blockage of lymph channels may result in elephantiasis to other areas of the body

Diagnosis and Treatment Skin scrapings mounted on KOH or Tissue biopsy Treatment Choices for therapy are limited with no drug giving satisfactory results. At present 5 flucytosine or thiabendazole and surgical excision are favoured when lesions are not too extensive particularly at early stage

Agents of Opportunistic Mycoses Diseases caused are seriously primarily to uncompromised individuals Found world wide Usually is part of the normal flora Not dimorphic

Candida albicans; Part of normal body flora in mucous membrane, dimorphic, germ tube at 37⁰C . Affect in the following: Cutaneous candidiasis Oral thrush especially in neonatal, diabetics, AIDS patients, and those receiving antibiotics or steroids. Vulvovaginitis is promoted by antibiotics use, high pH and diabetics mellitus

B) Chronic mucocutaneous candidiasis: T cell deficiency or endocrine defect eg hypo-parathyroidism, hypothyroidism hypoadrenalism, or thyoma are predisposing factors. C) Disseminated diseases In immunosuppressed cancer and transplant patient, candidal infection commonly present as disseminated diseases. Treatment; Ketoconazole and Fluconazole

Aspergillus fumigants and other A. species. Filamentous with septate, branched hyphae, fungus ball in lungs seen on radiolograph, induce allergic reactions. Pulmonary infection established in preexisting cavitary lesion and becomes invasive in immunocompromised patients, especially netropenic patients. Treatment: Surgery to remove tissue damaged, Amphotericn B and Intracunazole

Rhizopus and Mucor spp. Filamentas with broad , aseptate hyphae, hyphal embol Rhinocerebral zygomycosis (most common presentation) originates in paranasal sinuses and ocular orbit with possible spread to palate and brain. Usually seen in ketotic diabetics. Treatment: surgery to remove necrotic tissue, Amphotericin B

Pneumocystis carinii Most closely related to fungi, but sometimes classified as protozoan Interstitial pneumonia; occur only in severe immunocompromised individuals , especially AIDS patients. Gomori’s silver stain of lung tissue reveals diagnostics rounded, cup- shaped organism. Treatment: TMP/SMX, Pentamidine