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3rd cl ass
mycology lectures
No.1
Mycology
1-Mycology: Study of fungi
2-Mycoses: fungal infections
3-Mytoxicosis- intoxicaton
Mycology Basics
Kingdom: Fungi
More than 10 million species, but only ~400 human disease (*)
Sexual Groups
Ascomycota*
Basidiomycota*
Zygomycota*
Chytridia
Fungi Imperfecti*
-Very few species are in a commensal relationship with humans
- includes Candida albicans and Malasezia furfur
-Diseases caused by fungi are usually accidental
-Endogenous and Exogenous Sources
-Increasing problem due to antibacterial & immunosuppressive
agents
-Molecular mechanisms of pathogenesis not well-defined.
The 5 main groups
1-Clean up oil spills
2-Remove cyanide in mining operations
3-Neutralize dioxins and pesticides
4-Produce organic acids, sugars
5-Manufacture other commercial products.
- Fungi (yeast& molds)
are eukaryotic organisms whereas bacteria are
prokaryotic, they differ regarding;
1-Size-diameter
4 um-------1um
2-Nucleus.
3-Cytoplasm
4-Cell membrane,
Sterol---absent in bacteria
5- Cell wall,
Chitin ----peptidoglycane
6-Thermal dimorphism.
7-Metabolism
FUNGAL CELL WALL
-Consists of chitin not peptidoglycan like bacteria. Thus fungi are insensitive to
antibiotics as penicillins
-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
What is Medical Mycology ?
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.
MYCOTIC DISEASES (FOUR TYPES)
1. Hypersensitivity
• Allergy
2. Mycotoxicosis
• Production of toxin
3. Mycetismus (mushroom poisoning)
• Pre-formed toxin
4. Infection
PATHOGENIC FUNGI.
NORMAL HOST
• Systemic pathogens
- 25 species
• Cutaneous pathogens
- 33 species
• Subcutaneous pathogens
- 10 species
IMMUNOCOMPROMISED HOST
. Opportunistic fungi - 300 species.
In addition to those species which are generally recognized as
pathogenic to man it is firmly established that under unusual
circumstances of abnormal susceptibility of patient, or the traumatic
implantation of the fungus, other fungi are capable of causing lesions.
Those are called (Opportunistic Fungi.)
These circumstances may be
1. A debilitating condition of the
host, as Diabetes.
2. A concurrent disease such as leukemia.
3. Prolonged treatment with corticosteroids.
4.Immunosuppressive drugs or an antibiotic for long duration,
PORTAL OF ENTRY
1-SKIN
2-HAIR
3-NAILS
4-RESPIRATORY TRACT
5-GASTROINTESTINAL TRACT
6-URINARY TRACT
THE CLINICIAN MUST
1-COLONIZATION
2-FUNGEMIA
3-INFECTION
COLONIZATION Multiplication of an organism at a given site without
harm to the host,
INFECTION
Invasion and multiplication of organisms in body tissue
resulting in local cellular injury.
Morphology of Fungi
1. Filamentous fungi (molds)
2. Yeasts
3. Yeast-like fungi
4. 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.
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.
Colony Morphology
Yeasts
1-These occur in the form of round or oval bodies which reproduce by
the formation of buds known as blastospores.
2-Yeasts colonies resemble bacterial colonies in appearance and in
consistency.
3-The only pathogenic yeast in medical mycology is Cryptococcus
neoformans
Yeast-Like
1.These are fungi which occur in the form of budding yeast-like cells and
as chains of elongated unbranched filamentous cells which present the
appearance of broad septate hyphae. these hyphae intertwine to form a
pseudomycelium.
2. The yeast like fungi are grouped together in the genus Candida.
Candida Colonies
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 27Ċ
Histoplasma capsulatum 37Ċ
-
Medically Important Fungi
1-Deuteromycota- no sexual spores
2-Zygomycota- coenocytic fungi
3-Ascomycota– septate
– dust like spore
4-Basidomycota
– septate
– fleshy base; mushrooms
*Opportunistic mycoses*
1- Candidiasis
2- Aspergillosis,
3- Mucormycosis
4-Phycomycosis
Human fungal infection
A-Superficial
B-cutaneous
C-Subcutaneous.
D-Systemic
A-Superficial Fungal Infections
- Skin Infections
-limited to Stratum corneum
-do not penetrate deeper tissues
- No inflammation
1-Superficial mycoses
-Black piedra
-White piedra
2-Pityriasis versicolor.
3-tinea nigra
B-Cutaneous Mycoses
1-Dermatophytoses
2-Dermatomycoses
C-Subcutaneous Mycoses
-Caused by trauma [puncture]and introduction of the fungus and bacteria.
1-Chromoblasomycosis
2-Phaeohypomycosis
3-Mycetoma
4-Sporotrichosis
D-Systemic or Deep Mycoses
1-Histoplasmosis
2-Coccidiomycosis
3-Blastomycosis.
4-Cryptococcosis
Systemic mycosis disease pattern
1-Subacute respiratory infection
2-Acute infection
3-Severe disseminated infection
1-Systemic mycoses :subacute respiratory infection
1-Low fever
2-Non-productive cough
3-Mild & self-limiting
2-Systemic Mycoses: Acute infection
1- Productive cough
2-purulent sputum
3-pain in chest
4-Weight loss
5-night sweats
6-X-ray positive
--one, many lesions
-consolidation.
(Differential diagnosis: pneumonia, tumors).
Yeast Characteristics
1-solitary, unicellular
2-reproduction via budding
3-rounded shape
4-moist & mucoid colonies
Mould Characteristics
1-filamentous hyphae
2-hyphal formation
3-tips may be rounded
4-(conidia/spores )