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Batterjee Medical College. Dr. Manal El Said Head of Microbiology Department Mycology.

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Presentation on theme: "Batterjee Medical College. Dr. Manal El Said Head of Microbiology Department Mycology."— Presentation transcript:

1 Batterjee Medical College

2 Dr. Manal El Said Head of Microbiology Department Mycology

3 Batterjee Medical College 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). Structure & Growth Basic Mycology

4 Batterjee Medical College Basic Mycology Structure & Growth

5 Batterjee Medical College 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

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

7 Batterjee Medical College 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 Pathogenesis

8 Batterjee Medical College 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

9 Batterjee Medical College 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

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

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

12 Batterjee Medical College 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

13 Batterjee Medical College 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

14 Batterjee Medical College 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 Laboratory Diagnosis

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

16 Batterjee Medical College Fungi Causing Cutaneous & Subcutaneous Mycoses

17 Batterjee Medical College 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. Dermatophytes Trichophyton, Microsporum, Epidermophyton Species

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

19 Batterjee Medical College 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

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

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

22 Batterjee Medical College Sporothrix schenckii Pathogenesis Local abscess or ulcer with nodules in draining lymphatics.

23 Batterjee Medical College Fungi Causing Systemic Mycoses

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

25 Batterjee Medical College 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. 1-Histoplasma capsulatum Laboratory Diagnosis

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

27 Batterjee Medical College 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. 2-Coccidioides immitis Laboratory Diagnosis

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

29 Batterjee Medical College Disease Paracoccidioidomycosis. Characteristics Thermally dimorphic. Transmission Inhalation of airborne conidia. 4-Paracoccidioides brasiliensis Disease Characteristics Transmission

30 Batterjee Medical College Fungi Causing Opportunistic Mycoses

31 Batterjee Medical College Thrush, Disseminated candidiasis Chronic mucocutaneous candidiasis. Fungi Causing Opportunistic Mycoses 1-Candida albicans Disease 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.

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

33 Batterjee Medical College 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

34 Batterjee Medical College 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 Pathogenesis

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

36 Batterjee Medical College 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. Fungi Causing Opportunistic Mycoses 1-Candida albicans Laboratory Diagnosis Skin Test to determine competency of cell- mediated immunity. Out-pouching of cell wall that becomes tubular & does not have constriction at its base

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

38 Batterjee Medical College 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 2-Cryptococcus neoformans Pathogenesis

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

40 Batterjee Medical College 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 3-Aspergillus fumigatus Pathogenesis

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

42 Batterjee Medical College 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. Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species Pathogenesis


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