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Introduction mycology
1. INSTITUTE OF HEALTH TECHNOLOGY, DHAKA
Department of Laboratory Medicine
BSc in Health Technology (Laboratory)- 1st
Year
INSTITUTE OF HEALTH TECHNOLOGY, DHAKA
Department of Laboratory Medicine
BSc in Health Technology (Laboratory)- 1st
Year
MYCOLOGY
Lecture No. 01(Introduction)
ByBy
Sk. MIZANUR RAHMAN
Lecturer, Mycology
MS in Biotechnology & Genetic Engineering (UODA)
MS in Microbiology (SUB)
Sk. MIZANUR RAHMAN
Lecturer, Mycology
MS in Biotechnology & Genetic Engineering (UODA)
MS in Microbiology (SUB)
2. The Fungi
Learning outcomes- Students should be able to:
• Establish familiarity with the scientific terminology
peculiar to mycology
• Describe the dimorphic nature of the pathogenic fungi
used in making a clinical diagnosis.
• Emphasize the eukaryotic nature of the fungi.
• To explore the nature of the pathogenesis of fungal
infections.
• To gain familiarity with the classification of medically-
important fungi.
• To develop an understanding of the nature and mode of
action of anti-fungal agents
3. Recommended Textbooks
Theory
• Medical Mycology and Human Mycoses ES Beneke and AL
Rogers Star Publishing Company 1996 Belmont CA
Laboratory
• Identifying Filamentous Fungi: A Clinical Laboratory
Handbook St-Germain G and Summerbell R Rogers Star
Publishing Company 1996 Belmont CA
Additional Reading
• - Introductory Mycology Alexopoulos CJ Mims CW
Blackwell M Fourth Edition John Wiley &Sons Inc 1996 New
York NY
• - Medical Mycology KJ Kwon-Chung and JE Bennett Lea
&Febiger 1992 Philadelphia PA
• - Medical Microbiology A Laboratory Manual: Section II WG
Wu Third Edition Star Publishing Company 1995 Belmont CA
7. What is a Fungus ?
• Eukaryotic – a true nucleus
• Do not contain chlorophyll
• Have cell walls
• Produce filamentous structures
• Produce spores
8. Species of Fungi
• 100,000 – 200,000 species
• About 300 pathogenic for man
9. Fungal Morphology and Structure
Eukaryotic organisms, distinguished by a rigid
cell wall composed of chitin and glucan, and a
cell membrane in which ergosterol is
substituted for cholesterol as the major sterol
component.
Fungal taxonomy relies heavily on
morphology and mode of spore production
Fungi may be unicellular or multicellular.
The simplest grouping based on morphology
divides fungi into either yeast or mold forms.
10. Features of Fungi and its value in our
life:
The fungi are a ubiquitous and diverse organisms, that degrade
organic matter.
Fungi have heterotrophic life; they could survive in nature as:
Saprophytic: live on dead or decaying matter
Symbiotic: live together and have mutual advantage
Commensal: one benefits and other neither benefits nor
harmed.
Parasitic: live on or within a host, they get benefit and harm the
other.
Fungi mainly infect immunocompromised or hospitalized patients
with serious underlying diseases.
The incidence of specific invasive mycoses continues to increase
with time
The list of opportunistic fungal pathogens likewise increases each
year “It seems there are no non-pathogenic fungi anymore ! “
This increase in fungal infections can be attributed to the ever-
growing number of immunocompromised patients.
11. Characteristics of fungi
A. eukaryotic, non- vascular organisms
B. reproduce by means of spores (conidia), usually wind-
disseminated
C. both sexual (meiotic) and asexual (mitotic) spores may be
produced, depending on the species and conditions
D. typically not motile, although a few (e.g. Chytrids) have a motile
phase.
E. like plants, may have a stable haploid & diploid states
F. vegetative body may be unicellular (yeasts) or multicellular
moulds composed of microscopic threads called hyphae.
G. cell walls composed of mostly of chitin and glucan.
12. More Characteristics of Fungi
H. fungi are heterotrophic ( “other feeding,” must feed on
preformed organic material), not autotrophic ( “self feeding,”
make their own food by photosynthesis).
- Unlike animals (also heterotrophic), which ingest then digest,
fungi digest then ingest.
-Fungi produce exoenzymes to accomplish this
I. Most fungi store their food as glycogen (like animals). Plants
store food as starch.
K. Fungal cell membranes have a unique sterol, ergosterol, which
replaces cholesterol found in mammalian cell membranes
L. Tubule protein—production of a different type in microtubules
formed during nuclear division.
13. Structure
•The body of fungi is termed thallus (non-
reproductive)
•The thalli of yeast are small, globular and are single
celled
•The thalli of mold are composed of long, branched
tubular filaments called hyphae.
14. Structure
• The thallus of a mold is composed of hyphae
intertwined to form a tangled mass called
mycelium.
20. Classification of fungi
They are classified by several methods:
1- Morphological classification
2- Systematic classification
3- Clinical classification
23. 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
24.
25. Molds
• Multicellular, tubular structures (hyphae)
• Hyphae can be septate (regular crosswalls) or
nonseptate (coenocytic) depending on the
species (grow by apical extension)
– Vegetative hyphae grow on or in media (absorb
nutrients); form seen in tissue, few distinguishing
features
– Aerial hyphae contain structures for production of
spores (asexual propagules); usually only seen in
culture
26. • The fungal thallus consists of hyphae; a
mass of hyphae is a mycelium.
Molds
Figure 12.2
27. Moulds are multicellular organisms consisting of threadlike
tubular structures called Hyphae that elongate by apical
extension.
Hyphae are either:
Coenocytic: hollow and multinucleate
Septate: divided by partitions or cross-walls
Hyphae form together to produce a mat-like structure
called a Mycelium.
Vegetative hyphae, grow on or under surface of culture
medium,
Aerial Hyphae: project above surface of medium
Aerial H. produce Conidia (asexual reproductive elements)
Conidia can easily airborne and disseminate the fungus.
Many medical fungi are termed dimorphic because they exist
in yeast and mould forms.
31. Dimorphic Fungi
• Growth as a mold or as a yeast
• Most pathogenic fungi are dimorphic fungi
• At 37o
C yeast-like
• At 25o
C mold-like
• Can also occur with changes in CO2
• Fungi grow differently in tissue vs
nature/culture; often dictated by temp
32. • Some fungi are
dimorphic
depending on
environmental
conditions
• These organisms
produce both
yeast-like and
mold-like thalli
• Many are
pathogenic
• Candida albicans
Dimorphism
Figure 12.4
36. Subcutaneous Mycoses
• Confined to subcutaneous tissue and
rarely spread systemically. The
causative agents are soil organisms
introduced into the extremities by
trauma
37. Systemic Mycoses
• Involve skin and deep viscera
• May become widely disseminated
• Predilection for specific organs
38. Opportunistic Fungi
Ubiquitous saprophytes and occasional
pathogens that invade the tissues of
those patients who have:
• Predisposing diseases:
Diabetes, cancer, leukemia, etc.
• Predisposing conditions:
Agammaglobulinemia, steroid or antibiotic
therapy.
39. • Systemic mycoses Deep within body
• Subcutaneous mycoses Beneath the skin
• Cutaneous mycoses Affect hair, skin, nails
• Superficial mycoses Localized, e.g., hair
shafts
• Opportunistic mycoses Caused by normal
microbiota or
fungi
Fungal Diseases (mycoses)
53. Most serological tests for fungi
measure antibody. Newer tests
to measure antigen are now
being developed
ANTIGEN DETECTION PRESENTLY
AVAILABLE
Cryptococcosis
Histoplasmosis
Aspergillosis
54. Diagnosis
1. Wet Mount
2. Skin test
3. Serology
4. Fluorescent antibody
5. Biopsy and
histopathology
6. Culture
7. DNA probes
Bread Yeast
Bread yeast, or baker’s yeast, actually a type of sac fungi, reproduces by a process called budding. Bread yeast causes bread to rise by releasing carbon dioxide, which gets trapped in the dough. The Egyptians were the first to discover that allowing dough to ferment produced gases that made bread lighter.
Safra Nimrod/Phototake NYC MichaelA. McClure PHD/Phototake NYC
Yeasts grow typically in moist environments where there is a plentiful supply of simple, soluble nutrients such as sugars and amino acids. For this reason they are common on leaf and fruit surfaces, on roots and in various types of food. With few exceptions, they are unable to degrade polymers, such as starch and cellulose which are used by many hyphal fungi.
