2 Head of Microbiology Department MycologyDr. Manal El SaidHead of Microbiology Department
3 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).
5 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
6 Basic Mycology Structure & Growth Fungal cell wall is made of chitin Fungal cell membrane contains ergosterol.
7 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 & Sporothrixpyogenic response (composed of neutrophils).
8 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).
9 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.
10 Basic Mycology Fungal Toxins & Allergies Inhalation of spores of Aspergillus fumigatus can cause allergic bronchopulmonary aspergillosis.This is IgE-mediated immediate hypersensitivity response.
11 Basic Mycology Laboratory Diagnosis Microscopic examination of KOH preparation can reveal presence of fungal structures.KOH dissolve human cells, allowing visualization of fungi.
12 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.
13 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.
14 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.
15 Basic Mycology Antifungal Therapy Amphotericin B binds to fungal cell membranes at site of ergosterol disrupts integrity of membranesAzole drugs, such as itraconazole, fluconazole, & ketoconazole inhibit synthesis of ergosterol.Echinocandins inhibit synthesis of D-glucan, which (component of fungal cell wall).
17 Trichophyton, Microsporum, Epidermophyton Species DermatophytesTrichophyton, Microsporum, Epidermophyton SpeciesCutaneous (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.
18 Trichophyton, Microsporum, Epidermophyton Species DermatophytesTrichophyton, Microsporum, Epidermophyton SpeciesCharacteristicsThese fungi are molds that use keratin as nutritional source.Habitat is human skinTransmissionDirect contact with skin scales.
19 Trichophyton, Microsporum, Epidermophyton Species DermatophytesTrichophyton, Microsporum, Epidermophyton SpeciesDiseasesTinea 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 bodyTinea pedis - "athlete's foot". Infection of toe webs & soles of feet.Tinea unguium (onychomycosis)- nails. Clipped are used for cultureTinea capitis - head. Frequently found in childrenTinea cruris - "jock itch". Infection of groin, perineum or perianal area.Tinea barbae - ringworm of bearded areas of face & neck
21 Sporothrix schenckii Disease Sporotrichosis. Characteristics Thermally dimorphicHabitat is soil or vegetation.TransmissionMold spores enter skin in puncture wounds caused by rose thorns & other sharp objects in the garden.
22 Sporothrix schenckii Pathogenesis Local abscess or ulcer with nodules in draining lymphatics.
24 1-Histoplasma capsulatum DiseaseHistoplasmosis.CharacteristicsThermally dimorphicMold grows in soil enriched with bird droppingsTransmissionInhalation of airborne asexual spores
25 1-Histoplasma capsulatum Laboratory DiagnosisSkin TestHistoplasmin (mycelial extract) is the antigen.Useful for epidemiologic purposes to determine incidence of infection.Positive result indicates that infection has occurredIt cannot be used to diagnose active disease.Skin testing can induce antibodies, so serologic tests must be done first.
26 2-Coccidioides immitis DiseaseCoccidioidomycosis.CharacteristicsThermally dimorphic.Natural habitat is the soilTransmissionInhalation of airborne arthrospores.
27 2-Coccidioides immitis Laboratory DiagnosisSkin TestCoccidioidin, (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.
28 3-Blastomyces dermatitidis DiseaseBlastomycosis.CharacteristicsThermally dimorphicYeast form has single, broad-based bud & thick, refractile wall.Natural habitat is soilTransmissionInhalation of airborne spores (conidia).Transmission
29 4-Paracoccidioides brasiliensis DiseaseParacoccidioidomycosis.CharacteristicsThermally dimorphic .TransmissionInhalation of airborne conidia.DiseaseCharacteristicsTransmission
31 Fungi Causing Opportunistic Mycoses 1-Candida albicansDiseaseThrush,Disseminated candidiasisChronic mucocutaneous candidiasis.CharacteristicsCandida 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 whenincubated in serum at 37°C.
32 Fungi Causing Opportunistic Mycoses 1-Candida albicansTransmissionPart of the normal flora of skin, mucous membranes & GI tract.No person-to-person transmission.
33 Fungi Causing Opportunistic Mycoses 1-Candida albicansPathogenesisPredisposing factors include:- Reduced cell-mediated immunityAltered skin & mucous membraneSuppression of normal floraPresence of foreign bodies.Thrush is common in:Infantsimmunosuppressed patientspersons receiving antibiotic therapy.
34 Fungi Causing Opportunistic Mycoses 1-Candida albicansPathogenesisSkin 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.
35 Fungi Causing Opportunistic Mycoses 1-Candida albicansOral thrush. CDCCandida albicans showing germ tube production in serum.
36 Fungi Causing Opportunistic Mycoses 1-Candida albicansLaboratory DiagnosisMicroscopic 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
37 Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans DiseaseCryptococcosis, especially cryptococcal meningitis.CharacteristicsHeavily encapsulated yeast.Habitat is soil, enriched by pigeon droppings.TransmissionInhalation of airborne yeast cells.
38 Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans PathogenesisOrganisms cause influenza-like syndrome or pneumonia.They spread via the bloodstream to the meninges.Reduced cell-mediated immunity severe disease
39 Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus DiseaseInvasive aspergillosisAllergic bronchopulmonary aspergillosisAspergilloma (fungus ball).CharacteristicsMold with septate hyphae (branch at V-shaped angle) .Habitat is the soil.TransmissionInhalation of airborne spores (conidia).
40 Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus PathogenesisIn 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.
41 Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species DiseaseMucormycosis.CharacteristicsMolds with nonseptate hyphae that typically branch at 90-degree angle (wide-angle branching).Habitat is soil.TransmissionInhalation of airborne spores.
42 Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species PathogenesisThey 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.