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INTRODUCTION TO MEDICAL MYCOLOGY

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Title: INTRODUCTION TO MEDICAL MYCOLOGY


1
INTRODUCTION TO MEDICAL MYCOLOGY
Lecture 14
2
Learning Outcome
  • Able to define terms use in mycology
  • Can describe basic characteristic of fungi
  • Able to discuss fungal reproduction
  • Able to describe mycoses
  • Able to discuss laboratory examination for fungal
    infection.

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Definitions
  • Mycologists--scientists who study fungi
  • Mycology--scientific discipline dealing with
    fungi
  • Mycoses--diseases caused in animals by fungi
  • Mykos mycete fungus

5
  • I. FUNGI
  • Diverse group of heterotrophs.
  • Many are ecologically important saprophytes
    (consume dead and decaying matter)
  • Others are parasites.
  • Most are multicellular, but yeasts are
    unicellular.
  • Most are aerobes or facultative anaerobes.
  • Cell walls are made up of chitin
    (polysaccharide).
  • Over 100,000 fungal species identified. Only
    about 100 are human or animal pathogens.
  • Most human fungal infections are nosocomial
    and/or occur in immunocompromised individuals
    (opportunistic infections).
  • Fungal diseases in plants cause over 1 billion
    dollars/year in losses.

6
Characteristic of fungi
  • Vegetative Hypha
  • Composed of cells involved in catabolism and
    growth.
  • Reproductive Hypha (aerial)
  • Composed of cells involved in reproduction
    (produce spores).

7
General knowledge of the fungi
  • Both sexual and asexual spore may be produced
  • Store their food as glycogen (plant starch)
  • Fungi are heterotrophic organisms, lack of
    chlorophyll (plant autotrophic)

8
General knowledge of the fungi
  • Yeast unicellular, 370C
  • Budding Yeast may produce a pseudohypa
  • Fission yeast
  • Mold multicellular, hyphae, 250C
  • Dimorphic fungi (thermally dimorphic fungi)
    mold phase yeast phase

9
Yeasts
  • Facultative Anaerobes
  • Fermentation ethanol and CO2
  • Non-filamentous unicellular fungi
  • Spherical or oval
  • Reproduction
  • a) by fission, or
  • b). By budding

10
Yeast Reproduction
  • FISSION
  • even reproduction, nucleus divides forming two
    identical cells, like bacteria
  • BUDDING
  • uneven reproduction, parent cells nucleus
    divides and migrates to form a bud and then
    breaks away

11
YEAST
  • Unicellular
  • Micr. Oval to round
  • (Diameter 3-15 µm)
  • Macr. Pasty colonies (resemble
    bacteria)

12
MOULD
  • Multicellular
  • Micr. . Hypha(e) (dia 2-10 µm)
  • . Spores / conidia.
  • Macr. .Surface texture Cottony/ powdery/
    wooly/velvety/granular/glabrous
  • Pigmentation obverse reverse

13
General knowledge of the fungi
  • Eukaryotic microorganisms
  • Rigid cell walls chitin, glucans, mannans
  • Plasma membranes ergosterol
  • Lysine synthesis by L-? amino adipic acid (AAA)
    pathway and other organisms synthesize lysine by
    diaminopimelic acid (DAP) pathway

14
Fungal Structure
  • Thallus-body
  • Molds fleshy fungi have these structures
  • Long filaments of cells (hyphae)
  • Septate hyphae (cross wall) most fungi
  • Aseptate hyphae (coenocytic ) no cross wall,
    continous mass with many nuclei .
  • Mycelium
  • Abundance growth of aerial hyphae resulting a
    mass can be observed with unaided ayes

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Fungal Classification
  • Four groups of true fungi
  • Zygomycetes (common bread moldRhizopus)
  • Basidiomycetes (puffballs common mushrooms)
  • Ascomycetes (Dutch elm disease/rye smut)
  • Deuteromycetes (fungi imperfection)

18
Classification ( cont)
  • First three groups is based on their method of
    sexual reproduction
  • 4th group, the Deuteromycetes, have NO sexual
    reproduction

19
Fungi-Taxonomic classification
  • SEXUAL SPORE CLASS
  • Zygospore----------Zygomycetes
  • Basidiospore--------Basidiomycetes
  • Ascospore----------Ascomycetes
  • None/Unknown---- Deuteromycetes
  • (Fungi Imperfecti)

20
Zygomycetes
  • Asexual phaseSporangiumbread mold (Rhizopus
    stolonifer)
  • Sexual phase--- sporgangium ---shotgun fungus
    (lives on dung) it shoots its sporgangium
    explosively towards light or fly pathogen
    (Entomophthora muscae--these types of fungi have
    been used as agents for biological control of
    insects

21
Basidiomycetes
  • Basidiospore
  • Examples boletes, puffballs,smuts, stinkhorns
    and tooth fungi

22
Ascomycetes
  • Asexual phase-
  • Conidiospores (Penicillium and Aspergillus)
  • budding yeast
  • Sexual phase (morels, lichens )

23
Life Cycle
  • Fungal reproduce by 2 way
  • Asexual
  • Sexual
  • Asexual
  • Hyphae fragmentation
  • Asexual spores
  • Conidiosphore
  • Arthroconidia
  • Blastoconidia
  • sporangiospore

24
Reproduction of Fungi
  • 1. Sexual reproduction --Sexual spores
  • 2. Asexual reproduction--Asexual spores
  • 3. Parasexual reproduction--Genetic exchange

25
Life cycle
  • Conidiosphore
  • Spore that is not enclosed in sac

26
Life cycle
  • Athroconidia
  • Form fragmentation of hypae into single thick
    cells.

27
Life cycle
  • Blastoconidia
  • Buds coming from parents cells
  • Chlamydoconium a variant which spore form by
    thickening and enlargement within hypae

28
Life cycle
  • Sporangiospore
  • Spore form inside sporangium (sac) at the end of
    sporangiophore

29
Asexual Spores
  • Conidiospores
  • Chlamydospores
  • Sporangiospores
  • Blastospores
  • Arthrospore

30
Asexual spores ( cont)
  • Conidiospore
  • Multiple (chains) or single spores formed at the
    end of an aerial hypha
  • Not enclosed within a sac
  • Aspergillus spp.
  • Penicillium spp

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Aspergillus sp.
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Conidial Fungus
  • reproduces by means of asexual spores called
    conidia
  • Conidia vary greatly in shape, size and color
  • Most of the common household molds mildews are
    conidial fungi

35
Asexual spores ( cont)
  • Another type of Conidiophore
  • Blastospores
  • A bud coming off the parent cell
  • Candida albicans

36
  • Chlamydospore
  • Formed within hypha
  • Thick-walled spore
  • Candida albicans

37
Chlamydospores
  • The chlamydospore is a method of producing a
    substantial resting spore very quickly
  • Nutrient is shunted from adjacent cells into a
    preferred cell and it swells up, converts
    nutrient materials to oil droplets for efficient
    storage, then rounds off with a thick, often
    roughened outer wall for protection

38
Asexual spores
  • Sporangiospores
  • Hundreds formed within a sac (sporangium) at the
    end of an aerial hypha
  • Rhizopus spp.
  • Mucor spp
  • Absidia spp

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Types of asexual spores
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SEXUAL Spores
  • 1. Zygospore
  • 2. Ascospore
  • 3. Basidiospore
  • 4. Oospore

43
  • Sexual spores
  • Have three stages
  • Plasmogamy- a haploid nucleus of donor cells
  • Karyogamy- the () and (-) nuclei fuse to form a
    diploid zygote
  • Meiosis the diploid nucleus give rise to
    haploid nuclei (sexual spores) genetic
    recombinant

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MYCOSES
  • Superficial ( skin, hair, cornea)
  • Cutaneous ( Dermatophytosis )
  • Subcutaneous
  • True systemic (endemic)
  • Opportunistic

48
Zygomycosis
  • Disease caused by fungi that are classifiable as
    Zygomycetes
  • Mucormycosis Order Mucorales
  • Entomophthoromycosis Order Entomophthorales

49
Zygomycosis (cnt)
  • Presents as a spectrum of diseases, depending on
    the portal of entry and the predisposing risk
    factors of the patient
  • Rhinocerebral zygomycosis
  • Pulmonary zygomycosis
  • Gastrointestinal zygomycosis
  • Cutaneous zygomycosis
  • Disseminated zygomycosis

50
Material from the periorbital tissue of a woman
with poorly controlled diabetes mellitus with
facial and periorbital swelling due to
zygomycosis (see right picture) is stained with
periodic acid-Schiff stain (X 560). The material
demonstrates the classic appearance of
irregularly shaped broad hyphae with right-angle
branching (arrow).
http//www.emedicine.com/med/topic2438.htm
51
Laboratory to diagnosis of fungal infection
  • Specimen collection and transport
  • Specimen processing
  • Direct examination
  • Selection and inoculation of culture media
  • Identification

52
LABORATORY DIAGNOSIS OF MYCOSES
  • Direct microscopic examination
  • Culture
  • Serology

53
Specimen collection and transport
  • must be material from the actual infection site
  • must be carefully the contamination
  • must be established for the best chance of
    recovery of causative microorganisms (optimal
    times)

54
Specimen collection and transport ( cont)
  • must be obtained to perform the culture or other
    techniques request (sufficient quantity)
  • must be used to ensure optimal recovery of
    microorganisms
  • obtain cultures before the treatment
  • the culture container must be properly labeled

55
Specimen processing
  • specimen should be examined as soon as possible
  • direct examination
  • KOH mount
  • Calcofluor white
  • India ink
  • culture media

56
Selection and inoculation of culture media
  • Culture media for recovery of fungi from clinical
    specimens. PDA, Corn Starch Agar
  • The recovery rate may be somewhat enhanced by
    using a variety of isolation media,
    considerations of cost, storage, incubator space
    and technologist time.

57
Initial observations in the study of fungus
isolates
  • 1.Appearance of the growth
  • 2. Rate of growth
  • 3. Colony pigmentation
  • 4. Growth on media containing antifungal agents
  • 5.Dimorphic fungi

58
Initial observations in the study of fungus
isolates
  • 1.Appearance of the growth
  • - surface and reverse surface of colony
    were observed
  • - delicate or hairlike hyphae
  • 2. Rate of growth
  • - saprophytes 3-5 days
  • - dimorphic fungi 10 days or more
  • - dermatophytes 14 days or more

59
Initial observations in the study of fungus
isolates
  • 3. Colony pigmentation
  • 4. Growth on media containing antifungal agents
  • - most strains of the dimorphic fungi can
    grow
  • - most strains of the rapidly growing saprobes
    are
  • inhibited
  • 5. Dimorphic growth
  • - mold form (the environmental and infective
    form)
  • ambient or room temperature (22-25 OC)
  • - yeast form (invasive form)
  • near body temperature (30-35 OC)

60
Preparation of mounts for study
  • The tease mount
  • Scotch tape preparation
  • The microslide culture technique
  • ( slide culture )

61
Terms useful in the examination of fungi
  • hypha and pseudohyphae
  • mycelium
  • septate or aseptate (or coenocytic) hyphae
  • vegetative mycelium
  • aerial mycelium
  • reproductive mycelium

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Exercise
  • List 4 classes of fungi
  • List types of asexual spores
  • Diferentiate between conidiospore with
    sporangiospores
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