بسم الله الرحمن الرحيم 1 1 1

Head of Microbiology Department Mycology Dr. Manal El Said Head of Microbiology Department

Basic Mycology Structure & Growth Fungi are eukaryotic organisms that exist in two basic forms: yeasts & molds. Yeasts are single cells & reproduce by budding (daughter cells are unequal in size) Molds consist of long filaments of cells called hyphae & reproduce by cell division (daughter cells are equal in size).

Basic Mycology Structure & Growth

Basic Mycology Structure & Growth Some fungi are dimorphic, i.e., they can exist either as yeasts or molds, depending on temperature. - Room temperature (25°C) molds - Body temperature (37°C) yeasts

Basic Mycology Structure & Growth Fungal cell wall is made of chitin Fungal cell membrane contains ergosterol.

Basic Mycology Pathogenesis Infection with certain systemic fungi, such as Histoplasma & Coccidioides, granulomatous host defense response (composed of macrophages & helper T cells) & can be detected by skin tests. Infection with Aspergillus, Mucor & Sporothrix pyogenic response (composed of neutrophils).

Basic Mycology Fungal Toxins & Allergies Ingestion of Amanita mushrooms liver necrosis due to presence of two fungal toxins, amanitin & phalloidin.Amanitin inhibits RNA polymerase (synthesizes cellular mRNA).

Basic Mycology Fungal Toxins & Allergies Ingestion of peanuts & grains contaminated with Aspergillus flavus liver cancer due to presence of aflatoxin. Aflatoxin epoxide mutation in p53 gene loss of p53 tumor suppressor protein.

Basic Mycology Fungal Toxins & Allergies Inhalation of spores of Aspergillus fumigatus can cause allergic bronchopulmonary aspergillosis. This is IgE-mediated immediate hypersensitivity response.

Basic Mycology Laboratory Diagnosis Microscopic examination of KOH preparation can reveal presence of fungal structures. KOH dissolve human cells, allowing visualization of fungi.

Basic Mycology Laboratory Diagnosis Sabouraud's agar is used to grow fungi because its low pH inhibits growth of bacteria, allowing slower-growing fungi to emerge.

Basic Mycology Laboratory Diagnosis DNA probes can be used to identify fungi growing in culture at much earlier stage, i.e., when colony size is much smaller.

Basic Mycology Laboratory Diagnosis Tests for presence of fungal antigens & for presence of antibodies to fungal antigens are often used. Two commonly used tests in patient's serum are: - Cryptococcal antigen in spinal fluid - Coccidioides antibodies.

Basic Mycology Antifungal Therapy Amphotericin B binds to fungal cell membranes at site of ergosterol disrupts integrity of membranes Azole drugs, such as itraconazole, fluconazole, & ketoconazole inhibit synthesis of ergosterol. Echinocandins inhibit synthesis of D-glucan, which (component of fungal cell wall).

Fungi Causing Cutaneous & Subcutaneous Mycoses

Trichophyton, Microsporum, Epidermophyton Species Dermatophytes Trichophyton, Microsporum, Epidermophyton Species Cutaneous (Superficial) mycoses are confined to outer layers of skin, hair, & nails & do not invade living tissues. The fungi are called dermatophytes. Dermatophytes (keratinophilic fungi) , produce extracellular enzymes (keratinases) hydrolyzing keratin.

Trichophyton, Microsporum, Epidermophyton Species Dermatophytes Trichophyton, Microsporum, Epidermophyton Species Characteristics These fungi are molds that use keratin as nutritional source. Habitat is human skin Transmission Direct contact with skin scales.

Trichophyton, Microsporum, Epidermophyton Species Dermatophytes Trichophyton, Microsporum, Epidermophyton Species Diseases Tinea means "ringworm" or "moth-like". Dermatologists use term to refer to variety of lesions of skin or scalp. Tinea corporis - small lesions occurring anywhere on body Tinea pedis - "athlete's foot". Infection of toe webs & soles of feet. Tinea unguium (onychomycosis)- nails. Clipped are used for culture Tinea capitis - head. Frequently found in children Tinea cruris - "jock itch". Infection of groin, perineum or perianal area. Tinea barbae - ringworm of bearded areas of face & neck

Dermatophytes Tinea corporis Tinea pedis (athlete's foot) Trichophyton, Microsporum, Epidermophyton Species Tinea corporis Tinea pedis (athlete's foot) Onychomycosis "Tinea capitis Tinea faciei” Tinea cruris

Sporothrix schenckii Disease Sporotrichosis. Characteristics Thermally dimorphic Habitat is soil or vegetation. Transmission Mold spores enter skin in puncture wounds caused by rose thorns & other sharp objects in the garden.

Sporothrix schenckii Pathogenesis Local abscess or ulcer with nodules in draining lymphatics.

Fungi Causing Systemic Mycoses

1-Histoplasma capsulatum Disease Histoplasmosis. Characteristics Thermally dimorphic Mold grows in soil enriched with bird droppings Transmission Inhalation of airborne asexual spores

1-Histoplasma capsulatum Laboratory Diagnosis Skin Test Histoplasmin (mycelial extract) is the antigen. Useful for epidemiologic purposes to determine incidence of infection. Positive result indicates that infection has occurred It cannot be used to diagnose active disease. Skin testing can induce antibodies, so serologic tests must be done first.

2-Coccidioides immitis Disease Coccidioidomycosis. Characteristics Thermally dimorphic. Natural habitat is the soil Transmission Inhalation of airborne arthrospores.

2-Coccidioides immitis Laboratory Diagnosis Skin Test Coccidioidin, (mycelial extract) or spherulin, (extract of spherules) is the antigen. Determining if the patient has been infected. Positive test indicates prior infection but not necessarily active disease.

3-Blastomyces dermatitidis Disease Blastomycosis. Characteristics Thermally dimorphic Yeast form has single, broad-based bud & thick, refractile wall. Natural habitat is soil Transmission Inhalation of airborne spores (conidia). Transmission

4-Paracoccidioides brasiliensis Disease Paracoccidioidomycosis. Characteristics Thermally dimorphic . Transmission Inhalation of airborne conidia. Disease Characteristics Transmission

Fungi Causing Opportunistic Mycoses

Fungi Causing Opportunistic Mycoses 1-Candida albicans Disease Thrush, Disseminated candidiasis Chronic mucocutaneous candidiasis. Characteristics Candida albicans is yeast when part of normal flora of mucous membranes but forms pseudohyphae & hyphae when it invades tissue. The yeast form produces germ tubes when incubated in serum at 37°C.

Fungi Causing Opportunistic Mycoses 1-Candida albicans Transmission Part of the normal flora of skin, mucous membranes & GI tract. No person-to-person transmission.

Fungi Causing Opportunistic Mycoses 1-Candida albicans Pathogenesis Predisposing factors include: - Reduced cell-mediated immunity Altered skin & mucous membrane Suppression of normal flora Presence of foreign bodies. Thrush is common in: Infants immunosuppressed patients persons receiving antibiotic therapy.

Fungi Causing Opportunistic Mycoses 1-Candida albicans Pathogenesis Skin lesions occur on moisture-damaged skin. Disseminated infections, such as endocarditis and endophthalmitis, occur in immunosuppressed patients and intravenous drug users. Chronic mucocutaneous candidiasis occurs in children with a T-cell defect in immunity to Candida.

Fungi Causing Opportunistic Mycoses 1-Candida albicans Oral thrush. CDC Candida albicans showing germ tube production in serum.

Fungi Causing Opportunistic Mycoses 1-Candida albicans Laboratory Diagnosis Microscopic examination of tissue reveals yeasts & pseudohyphae. The yeast is gram-positive. Germ tube formation & production of chlamydospores distinguish C. albicans from other species of Candida. Skin Test to determine competency of cell-mediated immunity . Out-pouching of cell wall that becomes tubular & does not have constriction at its base

Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans Disease Cryptococcosis, especially cryptococcal meningitis. Characteristics Heavily encapsulated yeast. Habitat is soil, enriched by pigeon droppings. Transmission Inhalation of airborne yeast cells.

Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans Pathogenesis Organisms cause influenza-like syndrome or pneumonia. They spread via the bloodstream to the meninges. Reduced cell-mediated immunity severe disease

Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus Disease Invasive aspergillosis Allergic bronchopulmonary aspergillosis Aspergilloma (fungus ball). Characteristics Mold with septate hyphae (branch at V-shaped angle) . Habitat is the soil. Transmission Inhalation of airborne spores (conidia).

Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus Pathogenesis In immunocompromised patients, invasive disease occurs. It invades blood vessels thrombosis & infarction. Person with lung cavity, e.g., from tuberculosis, may develop "fungal ball" (aspergilloma). Allergic person, can develop allergic bronchopulmonary aspergillosis mediated by IgE antibody.

Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species Disease Mucormycosis. Characteristics Molds with nonseptate hyphae that typically branch at 90-degree angle (wide-angle branching). Habitat is soil. Transmission Inhalation of airborne spores.

Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species Pathogenesis They cause disease primarily in ketoacidotic diabetic and leukemic patients. Sinuses & surrounding tissue are typically involved. Hyphae invade mucosa & progress into underlying tissue & vessels, leading to necrosis & infarction.