2. Mycology

3. Terminology Mykos: Fungus Mycoses: A disease caused by a fungus
Mycology: Study of fungi

4. Characteristics of fungi
Widely distributed in nature (air, water, soil, decaying organic debris)
~400,000 types (Diverse habitats)
Eukaryotic, highly developed cellular structure
Facultatively anaerobic/strict aerobic
Chemotropic, nutrition: by absorption
Nonphotosynthetic (distinguishes them from plants and algae)
Some are aquatic – mainly fresh water, a few marine
Most are terrestrial – soil or on dead plant material

5. Characteristics of fungi
Crucial role in mineralisation of organic carbon
Many are parasites of terrestrial plants
A few are parasitic on animals including humans
Generally less important than bacterial or viral infections
Unicellular (yeasts) or filamentous
(molds).
Rigid cell wall, some are capsulated.
Spore bearing stages in the life cycle
Usually reproduce by sexual and asexual means
Insensitive to antibacterial antibiotics
they have a diploid number of chromosomes

6. Characteristics of fungi
Fungi can be beneficial or harmful
They are especially harmful to people who are compromised (opportunistic) or are in the hospital for other infections (nosocomial)
Fungi are important in the food chain because they decompose dead plant matter and recycle nutrients

7. Characteristics of fungi
Most fungi prefer a moist environment with a relative humidity of 70% or more.
Various species can grow at a temperature ranging from -6 to 50°C with optimaltemperature of 20 to 35°C.
Most fungi grow well at an acidic pH of 5.0 or lower and thus they grow well on fruits and many vegetables that are acidic in nature.

9. Structure and functions
A mass of hyphal elements is termed the mycelium (synonymous with mold).
Aerial hyphae often produce asexual reproduction propagules termed conidia(synonymous with spores).

10. Relatively large and complex conidia are termed macroconidia while the smaller and more simple conidia are termed microconidia.
When the conidia are enclosed in a sac (the sporangium), they are called endospores.
The presence/absence of conidia and their size, shape and location are major features used in the laboratory to identify the species of fungus in clinical specimens.

12. Major polysaccharides of fungal cell wall
POLYMER MONOMER
Chitin N-acetyl glucosamine
Chitosan D-Glucosamine
Cellulose D-Glucose
-Glucan D-Glucose
-Glucan D-Glucose
Mannan D-Mannose
The type and amount of the polysaccharide vary from one fungal species to other.

14. What are the differences between Fungi and Bacteria?

15. Figure: 02-01a-b
Caption:
Internal structure of microbial cells. (a) Diagram of a prokaryote. (b) Diagram of a eukaryote.

16. Metabolism
For medical purposes the important aspects of fungal metabolism are the synthesis of: chitin a polymer of N-acetyl glucosamine, rather than peptidoglycan_ a characterestic component of bacterial cell wall.
Fungi are there for unaffected by antibiotics (for example penicillin) that inhibit peptidoglycan synthesis

17. ergosterol
for incorporation into the plasma membrane.
This makes the plasma membrane sensitive to those antimicrobial agents which either
- block the synthesis of ergosterol or
- prevent its incorporation into the membrane or - bind to it, e.g. amphotericin B

18. The synthesis of toxins such as:
a. Ergot alkaloids- these are produced by Claviceps purpurea
b. Aflatoxins - these are carcinogens produced by Aspergillus flavus when growing on grain.
When these grains are eaten by humans or when they are fed to dairy cattle and they get into the milk supply, they affect humans.

19. The synthesis of proteins on ribosomes that are different from those found in bacteria.
This makes the fungi immune to those antimicrobial agents that are directed against the bacterial ribosome, e.g., chloramphenicol.

21. Penicillium (Source of penicillin)
In Penicillium, phialides may be produced singly, in groups or from branched metulae, giving a brush-like appearance known as a penicillus
Morphological structures and types of conidiophore branching in Penicillium. a. simple; b. one-stage branched; c. two-stage branched; d. three-stage branched

22. Penicillin kills bacteria by interfering with their ability to synthesize cell wall.
Penicillin quickly became a primary treatment for pneumonia, diphtheria, syphilis, gonorrhea, scarlet fever, and many other infections. For “the discovery of penicillin and its curative effect in various infectious diseases” Fleming, Chain, and Florey received the Noble Prize for Medicine in 1945.
In this sequence, Escherichia coli were incubated in penicillin for 30 minutes. The bacteria lengthen, but cannot divide. Eventually the weak cell wall ruptures (last panel).

23. Fungi as human pathogens
Among the species of fungi that have been described, fewer than 200 have been associated with human disease

24. Diseases Caused by Fungi
Diseases caused by fungal cells are called (Mycosis).
Diseases caused by fungal spores are called (Allergy), either respiratory or skin allergy.
Diseases caused by fungal byproducts, mycotoxins, are called (Mycotoxicosis).

25. Fungi- Morphological Classification
Yeast: Unicellular (grows at 37 C)
Mould: Multicellular (grows
at 25 C)
Dimorphic: growing in
mould or yeast form

28. Yeast Budding Mother and Daughter Cells

29. Molds are made of hyphae (cells joined in thread-like strands)
MODULAR GROWTH - FRAGMENTATION = ASEXUAL REPRODUCTION!!

30. Classification of Hyphae
BASED ON: A. Existence of septa Septate Nonseptate B. Shape and Morphology Racquet Spiral Nodular Root-like (rhizoid) Pectinate Chandler

31. Septa - Regular cross-walls formed in hyphae.
Hyphae with septa are septate.
Those lacking septa except to delimit reproductive structures and aging hyphae are called aseptate or coenocytic.

35. Mono and Di Karyotic
– Monokaryotic: each compartment has a single nucleus
– Dikaryotic: two distinct nuclei within each hyphae compartment

36. Hetero and Homo Karyotic
– Heterokaryotic: dikaryotic or multinucleate hypha has nuclei from genetically distinct individuals – Homokaryotic: hyphae whose nuclei are genetically similar to one another

37. DIMORPHIC
Capable of growing in mould or yeast form under different environmental conditions (temperature, CO2, nutrients)
Some fungal species, specially those that cause systemic mycoses,are dimorphic.

38. Fungal reproduction Anamorph= asexual stage
Mitospore=spore formed via asexual reproduction (mitosis), commonly called a conidium or sporangiospore
Teleomorph= sexual stage
Meiospore=spore formed via sexual reproduction (e.g., resulting from meiosis), type of spore varies by phylum

40. Identification of Fungal Species
The presence/absence of conidia and their size, shape and location are major features used in the laboratory to identify the species of fungus in clinical specimens.

41. Asexual fruiting structure of Rhizopus species
Asexual fruiting structure of Rhizopus species, illustrating sporangium, sporangiophore, sporangiospores, coenocytic hyphae and rhizoids.

42. Asexual fruiting structure of Aspergillus species
Asexual fruiting structure of Aspergillus species, illustrating septate hyphae, conidiophore, vesicle, phialides and conidiospores

43. Asexual fruiting structure of Penicillium species
Asexual fruiting structure of Penicillium species, illustrating septate hyphae, conidiophore and conidiospores

44. Asexual Reproduction by Budding in Yeast
The cell grows and divides into two daughter cells that each contain the information and machinery necessary to repeat the process.

45. Budding Yeast

48. ASEXUAL SPORES 1. Arthrospore 2. Blastospore (Budding in Yeast)
3. Chlamydospore
4. Macroconidium (Relatively large)
5. Microconidium (Relatively small)
6. Sporangiospore (Sporangia)

50. Kingdom Fungi Division Chytridiomycota Division Ascomycota
Division Glomeromycota
Division Basidiomycota
Division Zygomycota
Division Deuteromycota

51. ? Fungus-like protist Deuteromycota Chytrids (1,000 species)
Hyphae
25 µm
Chytrids (1,000 species)
Fungus-like protist
Zygomycetes (1,000 species)
Fungal hypha
Glomeromycetes (160 species)
Ascomycetes (65,000 species)
Basidiomycetes (30,000 species) ?
Deuteromycota

52. The five fungal phyla can be distinguished by their reproductive features.

53. Division Chytridiomycota
mainly aquatic.
Some are saprobes, while others parasitize protists, plants, and animals.
chitinous cell wall
flagellated zoospores
the most primitive fungi

54. Division Ascomycota “Sac fungi” (truffles, yeast)
Beer > 6,000 years
Wine > 8,000 years
Lichens
Decomposers, pathogens
“yeast” describes a form of fungi (i.e., non-hyphal)
60,000 species

55. Division Ascomycota
Scarlet cup
Morchella
truffles

56. Division Ascomycota
Close up of cheese showing blue-green mycelium of Penicillium roqueforti.
Roquefort cheese

57. LICHENS
Yeast
Lichen

58. Division Glomeromycota
Previously With Zygomycota
Small Monophyletic Clade
Endomycorrhizae – Arbuscular Mycorrhizae
Produce branching Arbuscules

59. Plant-Fungal Relationships
Mycorrhizae (“fungus roots”)
90% of tree species have this association
Very important to absorption of water and nutrients

60. Soil surface
Plant roots
Mycorrhizae
Increases s.a. for absorption

61. Division Basidiomycota
“Club fungi” (mushrooms)
Club-shaped reproductive structure
Food
Plant diseases
25,000 species

63. Fairy Ring

64. Division Zygomycota e.g. Rhizopus sp. (Black bread Mold)

65. Zygomycosis
Caused by:
Rhizopus sp.
Absidia sp.
Mucor sp.

66. Candidiasis caused by Candida albicans
Candidiasis or yeast infection
Can be thrush (oral) or vulvovaginal candidiasis
Found in newborns, AIDS patients, and in people who have just completed antibiotic
Is also one cause of diaper rash!

67. Yeast Infections

68. Division Deuteromycota
Spores produced by the species in this category are not quite so easy to categorize by shape.
Penicillium
Organisms from this phylum are both beneficial (penicillin from Penicillium, soy sauce and citric acid from Aspergillus) and very harmful (Aspergillus can be toxic if inhaled).

69. Aspergillus sp.

70. Aspergillosis
Aspergillus causes aspergillosis

71. Penicillium sp.

73. Clinical Mucology

74. Classification of Fungal Infections
In general, humans have a high level of innate immunity to fungi and most of the infections they cause are mild and self-limiting.
This resistance is due to:
Fatty acid content of the skin
mucosal surfaces
body fluids
Epithelial turnover

75. Normal flora
Transferrin
Transferrin is a blood plasma protein binds iron, thus creating an environment low in free iron, where few microbes are able to survive – associated with the innate immune system
Cilia of respiratory tract

76. Fungal diseases Any fungal infection is a mycosis
These are long lasting and hard to treat
Classify these into 4 groups according to degree of tissue involvement and mode of entry into host:
1- Systemic (endemic)
2- subcutaneous
3- Cutaneous
4- opportunistic

77. Systemic Infections deep in the body
Can affect a number of tissues and/or organs
Usually caused by inhalation of spores from fungi that live in the soil
Infections that originate primarily in the lung and may spread to many organ systems.
Include histoplasmosis and coccidioidomycosis

78. Saprobic Phase Parasitic Phase
Systemic mycoses
(1) Histoplasma capsulatum (causing histoplasmosis)
Dimorphic with mold to yeast transition when infecting susceptible species.
Yeast cells are relatively small.
Saprobic phase shows tuberculate macroconidia
Saprobic Phase      Parasitic Phase

79. Saprobic Phase Parasitic Phase
Systemic mycoses
(2) Blastomyces dermatitidis (causing blastomycosis)
Dimorphic with mold to yeast transition when infecting susceptible species.
Yeast cells are medium size with thick walls.
Saprobic Phase            Parasitic Phase

80. Saprobic Phase Parasitic Phase
Systemic mycoses
(3) Paracoccidioides brasiliensis (causing paracoccidiodomycosis)
Dimorphic with mold to yeast transition when infecting susceptible species.
Yeast cells have multiple buds
Saprobic Phase            Parasitic Phase

81. Saprobic Phase Parasitic Phase
Systemic mycoses
(4) Coccidioides immitis (causing coccidioidomycosis)
Dimorphic with mold to spherule transition when infecting susceptible species. Spherules are multinucleate.
Saprobic Phase            Parasitic Phase

82. Saprobic Phase Parasitic Phase
Systemic mycoses
(5) Cryptococcus neoformans (causing a severe form of meningitis in people with HIV infection and AIDS).
Monomorphic with yeast phase only.
Saprobic Phase            Parasitic Phase
This is the only pathogenic yeast with a capsule.
The capsule is extremely large.

83. subcutaneous Infections beneath the skin
Infections involving the dermis, subcutaneous tissues, muscle or bone
It Caused by saprophytic fungi that live in soil or on vegetation
Often enter through puncture wound
Example is sporotrichosis

84. Identification of Organism
Subcutaneous mycoses
Disease 
Etiological Agent
Symptoms
Identification of Organism
Sporotrichosis 
Sporothrix schenckii 
Nodules and ulcers along lymphatics at site of inoculation
Budding yeast in tissue exudate that converts to mold with "rosette pattern" of conidiation on culture at 25oC. 
Chromoblastomycosis 
Fonsecaea pedrosoi 
Fonsecaea compacta 
Wangiella dermatitidis 
Warty nodules that progress to "cauliflower-like" appearance at site of inoculation 
Copper-colored spherical yeast called "Medlar bodies" in tissue 
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

85. Cutaneous
Fungi that infect only hair, epidermis, and nails are dermatophytes or cutaneous mycoses
These produce an enzyme that degrades keratin (keratinase)
Can spread by contact (human/human, animal/human)
All of the dermatophytic diseases are caused by members of three genera, Microsporum, Trichophyton and Epidermophyton, which comprise 41 species.

86. - They do not invade underlying, non keratinized tissues.
- There is some specificity, however.
Whereas all three organisms attack the skin, Microsporum does not infect nails, and Epidermophyton does not infect hair.
- They do not invade underlying, non keratinized tissues.
Tinea capitis of the scalp caused by Microsporum gypseum

87. Indentification of organism
Cutaneous mycoses
Disease 
Etiological Agent 
Symptoms
Indentification of organism
Tinea capitis 
Microsporum sp. Trichophyton sp. Epidermophyton sp. 
ringworm lesion of scalp
presence/absence and shape of micro- and macroconidia in scrapings from lesion 
Tinea corporis 
Microsporum sp. Trichophyton sp. Epidermophyton sp
ringworm lesion of trunk, arms, legs 
Tinea manus
ringworm lesion of hand
Tinea cruris "jock itch"
ringworm lesion of groin
Tinea pedis"athlete's foot"
ringworm lesion of foot
Tinea unguium
infection of nails
presence/absence and shape of micro- and macroconidia in scrapings from lesion
Ectothrix
infection of hair shaft surface 
mycelium and spores on hair shaft 
Endothrix
infection of hair shaft interior
mycelium and spores in hair shaft

88. Opportunistic mycoses
Harmless in normal habitat but can become pathogenic if given the ‘opportunity’
Infections in patients with immune deficiencies who would otherwise not be infected
Opportunistic mycoses are seen in those people with impaired host defenses such as occurs in:  
AIDS
Alteration of normal flora
Diabetes mellitus
Immunosuppressive therapy
Malignancy

89. Opportunistic mycoses
Disease 
Etiological Agent
Symptoms
Identification of organism
Candidiases
Candida albicans
Creamy growth on various areas of body
Budding yeast, septate hyphae, pseudohyphae in tissue. Germ tubeformation in serum
Aspergillosis 
Aspergillus fumigatus 
"Fungus ball" in tissue 
Morphology of asexual fruiting structure 
Zygomycosis
Rhizopus sp. Absidia sp. Mucor sp. 
Various
Morphology of asexual fruiting structure and mycelium

90. LABORATORY DIAGNOSIS OF MYCOSES
Direct microscopic examination
Gram, potassium hydroxide (KOH), calcofluor white, India ink
Culture
Sabouraud dextrose agar
Mycobiotic agar
Serology

91. LABORATORY DIAGNOSIS OF MYCOSES
Visualization of fungi in human tissue preparations 1. Treatment with 10% potassium hydroxide 2. Positive stain with: a. Lactophenol cotton blue b. Grocott silver stain c. Hematoxylin d. Eosin 3. Negative stain with India ink Fluorescence of fungi under ultraviolet light

92. Gram Stain of tissue infected with Cryptococcus neoformans
Stained Fungi
Gram Stain of tissue infected with Cryptococcus neoformans
India Ink of Cerebro-Spinal Fluid (CSF)
with Cryptococcus neoformans
Hematoxylin-eosin-stained section of cerebral cortex demonstrating septate hyphal elements.

93. Clinical Techniques in Mycology
Culture of fungi on
1. Sabouraud's agar (favors fungal growth because of low pH)
2. Mycosel agar (selective for pathogenic fungi because of chloramphenicol and cycloheximide in medium)
Visualization of cultured fungi (25oC and 37oC)
1.    Colony morphology
2.    Cellular morphology
a.    Hyphal morphology  
(1)    Aseptate or coenocytic
(2)    Septate
(a)    Regular connection
(b)    Clamp connection

94. Thanks