Eukaryotic Organism Posses at Least One Nucleus Nuclear Membrane, Endoplasmic

8/14/2019 Eukaryotic Organism Posses at Least One Nucleus Nuclear Membrane, Endoplasmic

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Mycology

Eukaryotic organism

Posses at least one nucleus nuclear

membrane, endoplasmic reticulum,and mitochondria

Lacks the property of photosynthesis


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two basic morphological forms

Yeasts are unicellular fungi which reproduce asexually

by blastoconidia formation (budding) or fission

Hyphae multi-cellular fungi which reproduce asexually and/or

sexually

**Dimorphism is the condition where by afungus can exhibit either the yeast form or the

hyphal form, depending on growth conditions


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Morphology

Thallus- vegetative portion of a fungus

Hypha- filamentous or thread like of a

thallus Non septate- without partition

Septate- with partition

Pectinate- with comblike lateral projection

Spiral- with terminal cells


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Mycelium- mass of countless hyphaesynonymous to mold

Spores ( conidia )- reproduction Asexual spore- resistant to adverse

growth condition Thallospores- derived from the cells of the

thallus or body of the fungus

Blastophores- buds from yeast Chlamydospores arthrospores


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Conidia- macroconidia, microconidia


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Asexual spore Ascospores- results from asexual

production involving saclike structure

called ascus Basidiospores- spores produces from the

surface of a special structure calledbasidium

Oospores- formed when two asexuallyformed spores unite


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Fungal metabolism


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All fungi are free living they are not obligate intracellular

parasites do not contain chlorophyll and cannot

synthesize macromolecules fromcarbon dioxide and energy derived

from light rays. Therefore all fungi are heterotrophs,

living on preformed organic matter


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important aspects of fungalmetabolism are:

The synthesis of chitin, a polymer ofN-acetyl glucosamine, and othercompounds, for use in forming thecell wall. These induce immunehypersensitivity .


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The synthesis of ergosterol forincorporation into the plasmamembrane. This makes the plasmamembrane sensitive to thoseantimicrobial agents which eitherblock the synthesis of ergosterol or

prevent its incorporation into themembrane or bind to it,

e.g. amphotericin B.


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The synthesis of proteins onribosomes that are different fromthose found in bacteria. This makesthe fungi immune to thoseantimicrobial agents that are directedagainst the bacterial ribosome, e.g.,

chloramphenicol.


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The ability of certain metabolites toalter morphology of yeast and/or beassimilated by yeast with concomitantclinical identification affects.


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Synthesis of toxin

Ergot alkaloids- these are producedby Claviceps purpurea and cause analpha adrenergic blockade

Psychotropic agents - these includepsilocybin, psilocin and lysergic aciddiethylamide (LSD)


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Aflatoxins - these are carcinogensproduced byAspergillus flavus whengrowing on grain. When these grainsare eaten by humans or when theyare fed to dairy cattle and they getinto the milk supply, they affect

humans.


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Clinical Techniques inMycology


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A. Visualization of fungi in tissuepreparations

Treatment with 10% potassiumhydroxide

Positive stain with a. Lactophenol cotton blue

b. Grocott silver stain

c. Hematoxylin

d. Eosin

3. Negative stain with India ink


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Fluorescence of fungi underultraviolet light

Culture of fungi on 1. Sabouraud's agar (favors fungalgrowth because of low pH)

2. Mycosel agar (selective for pathogenic

fungi because of chloramphenicol andcycloheximide in medium)


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Visualization of cultured fungi (25oC and37oC) Colonial morphology Cellular morphology

Identification of yeast by Biochemical tests Behavior in broth and serum (germ tube

formation) Behavior on cornmeal agar (pseudohyphae

formation)


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Mycoses

Superficial

Cutaneous

Subcutaneous Systemic or deep mycoses

Mycoses due to opportunistic fungi


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Superficial Mycoses

Tinea versicolor- caused by Malasseziafurfur AKA pitysporum orbiculare

Tinea nigra- caused by exophiala werneckii,

cause dark pigmented patches on the skin Tinea nodosa (black piedra)- caused by

piedraia hortae which characteristically formhard nodules along parasitized hair


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White piedra- caused by trichosporonbeiglelii, development of soft ovalnodules adhering to the hair

Disease Etiological Agent Symptoms Identification of organism


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Pityriasis versicolor Malassezia furfur hypopigmented macules "spaghetti and meatballs" appearanceof organism in skin scrapings

Tinea nigra Exophiala werneckii black macules black, 2-celled oval yeast in skinscrapings

Black piedra Piedraia hortai black nodule on hair shaft black nodule on hair shaft composed ofspore sacs and spores

White piedra Trichosporum beigelii creme-colored nodules on hair shaft white nodule on hair shaft composed ofmycelia that fragment into arthrospores


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Tinea versicolor


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Tinea nigra


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Black piedra


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Cutaneous mycosis

infections that extend deeper into theepidermis, as well as invasive hair andnail diseases.

These diseases are restricted to thekeratinized layers of the skin, hair andnails

The agents causing these diseases aretermed dermatophytes. The diseasesare referred to as ringworm or tinea.


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Tinea capitis, tinea favosa- microsporum andtricophyton.

Tinea barbae

Tinea corporis- face and trunk Tinea cruris- affecting groin

Tinea axilliaris

Tinea pedis

Tinea manuum Tinea unguim

Disease Etiological Agent Symptoms Indentification of organism


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Tinea capitis Microsporum sp. Trichophyton sp.Epidermophyton sp.

ringworm lesion of scalp Presence/absence and shape of micro-and macroconidia in scrapings fromlesion

Tinea corporis Microsporum sp. Trichophyton sp.Epidermophyton sp

ringworm lesion of trunk, arms, legs Presence/absence and shape of micro-and macroconidia in scrapings from

lesion

Tinea manus Microsporum sp. Trichophyton sp.Epidermophyton sp

ringworm lesion of hand Presence/absence and shape of micro-and macroconidia in scrapings fromlesion

Tinea cruris "jock itch" Microsporum sp. Trichophyton sp.

Epidermophyton sp

ringworm lesion of groin Presence/absence and shape of micro-

and macroconidia in scrapings fromlesion

Tinea pedis"athlete's foot" Microsporum sp. Trichophyton sp.Epidermophyton sp

ringworm lesion of foot Presence/absence and shape of micro-and macroconidia in scrapings fromlesion

Tinea unguium Microsporum sp. Trichophyton sp.Epidermophyton sp infection of nails Presence/absence and shape of micro-and macroconidia in scrapings fromlesion

Ectothrix Microsporum sp. Trichophyton sp.Epidermophyton sp

infection of hair shaft surface Mycelium and spores on hair shaft

Endothrix Microsporum sp. Trichophyton sp.

Epidermophyton sp

infection of hair shaft interior Mycelium and spores in hair shaft


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Tinea fovosa


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Tinea barbae


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Tinea corporis


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Tinea cruris


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Tinea cruris 2


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Tinea pedis


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Subcutanoues mycoses

infections involving the dermis,subcutaneous tissues, muscle andfascia

These infections initially involve thedeeper layers of the dermis,subcutaneous tissue or bone


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Sporotrichosis- sphorothrix schenkii, starts withthe subcutaneous nodule followed by the chainof draining ulcers

Chromoblastomycosis- granulomatousverrucose ulcerative infection, painless unlesscomplicated by bacteria Phialophora verrucosa

Cladosporium carrionii

Fonsecaea pedrosi

Fonsecaea compactum


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Mycetoma Pseudallescheria boydii

Madurella grisea

Madurella mycetomatis

Draining sinus tracts at site of inoculation

White, brown, yellow or black granules in

exudate that are fungal colonies


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keratomycosis


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sporotrichosis


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Systemic mycoses

infections that originate primarily inthe lung and may spread to manyorgan systems.

Unlike most other fungi, the fivesystemic mycotic agents areinherently virulent. Each species has

biochemical and structural


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Systemic mycosis

Coccidiodes immitis- coccidiomycosis Histoplasma capsulatum- agent of

histoplasmosis which involves the lungs,

spleen, lymph glands, kidneys and brain- KOH is not useful in the diagnosis butbuffy coat, bone marrow and lymphnodes biopsy or mucosal scrappings


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Cryptococcus neoformans- subacute orchronic infection that involves the CNS

Blastomyces dermatidis- chronic

granulomatous and suppurative conditionthat involves the lungs and the pleuraethat simulates tuberculosis

Candida albicans- infection that involvesnails, vulvo-vagina, CNS, pericardium,lungs


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Nocardia asteroides- chronicgranulomatous condition of the lungsand the CNS

Aspergillus- associated with prolongsantibiotic therapy


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histoplasmosis


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cryptococcosis


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cryptococcosis


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candidiasis


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aspegillus


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Opportunistic mycosis

infections in patients with immune deficiencies whowould otherwise not be infected

Opportunistic mycoses are seen in those people withimpaired host defenses such as occurs in

AIDS Alteration of normal flora Diabetes mellitus Immunosuppressive therapy

Malignancy

Disease Etiological Agent Symptoms Identification of organism


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Candidiases Candida albicans Creamy growth on various areas ofbody

Budding yeast, septate hyphae,pseudohyphae in tissue. Germtubeformation in serum

spergillosis Aspergillus fumigatus "Fungus ball" in tissue Morphology of asexual fruiting structure

Zygomycosis Rhizopus sp.Absidia sp. Mucorsp. Various Morphology of asexual fruiting structureand mycelium


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Eukaryotic Organism Posses at Least One Nucleus Nuclear Membrane, Endoplasmic