Presentation regarding 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.

4. 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 cell’s
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

17. Fungal Classification
Four groups of true fungi
–Zygomycetes (common bread mold—Rhizopus)
–Basidiomycetes (puffballs & common mushrooms)
–Ascomycetes (Dutch elm disease/rye smut)
–Deuteromycetes (fungi imperfection)

18. Classification ( con’t) :
• 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 phase—Sporangium—bread 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 ( con’t)
Conidiospore
– Multiple (chains) or single spores formed at
the end of an aerial hypha
– Not enclosed within a sac
• Aspergillus spp.
• Penicillium spp

32. Aspergillus sp.

34. 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

40. Types of asexual spores

42. 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

47. 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 (cn’t)
• 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
( con’t)
• 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

65. Exercise
1. List 4 classes of fungi
2. List types of asexual spores
3. Diferentiate between conidiospore with
sporangiospores