13.Introduction to Mycology

7/27/2019 13.Introduction to Mycology

1/77

INTRODUCTION TO

MEDICAL MYCOLOGY

Lecture 14


2/77

Mycology

Myco- fungus

Logy - study


3/77

Definitions

Mycologists--scientists who study fungi

Mycology--scientific discipline dealing

with fungi

Mycoses--diseases caused in animals by

fungi

Mykos = mycete = fungus


4/77

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).


5/77

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 1billion dollars/year in losses.


6/77

General knowledge of the

fungi Eukaryotic microorganisms

Rigid cell walls: made from chitin, glucans,

mannans

Plasma membranes: made from ergosterol

Lysine synthesis by L- amino adipic

acid (AAA) pathway.


7/77


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)


8/77


fungi Yeast : unicellular, 370C

Mold : multicellular, hyphae, 250C

Dimorphic fungi (thermally dimorphicfungi) : mold phase & yeast phase


9/77

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 .


10/77


11/77


12/77


13/77

Yeasts

Facultative Anaerobes

Fermentation : ethanol and CO2

Non-filamentous unicellular fungi Spherical or oval

Reproduction:

a) fission,b). budding


14/77

Yeast Reproduction

FISSION

even reproduction, nucleus divides

forming two identical cells, like bacteria

BUDDING

uneven reproduction, parent cells

nucleus divides and migrates to form abud and then breaks away


15/77

YEAST

Unicellular

Microscopy.: Oval to round

(Diameter : 3-15 m)

Macroscopy.: Pasty colonies

(resemble bacteria)


16/77

Yeast


17/77

MOULD

Multicellular

Micr.: . Hypha(e) (dia: 2-10 m)

. Spores / conidia.

Macr.: .Surface texture: Cottony/ powdery/

wooly/velvety/granular/glabrous

Pigmentation :obverse & reverse


18/77

MOULD

Hypha : septate, aseptate

Mycelium: a. Vegetative

b. Aerial /fertile/

reproductive


19/77

Classification of Hyphae

A. Existence of septa Septate

Nonseptate ( coenocytic )B. Shape and Morphology

Racquet -

Spiral -

Nodular - Rhizoid -Root-like

Pectinate -

Favic - chandelier


20/77

Dimorphic Fungi

Capable of growing in mould oryeast form under different

environmental conditions(temperature, CO2, nutrients)


21/77

Fungal Classification

Four groups of true fungi

Zygomycetes (common bread moldRhizopus) Basidiomycetes (puffballs & common mushrooms)

Ascomycetes (Dutch elm disease/rye smut)

Deuteromycetes (fungi imperfection)


22/77

Classification ( cont) :

First three groups is based on their

method of sexual reproduction

4th group, the Deuteromycetes, have NO

sexual reproduction


23/77

Asexual Reproduction

The progeny will be identical to parent:

Spores are called Conidiospores

Blastospores,

Chlamydospores

Sporangiospores

Fragmentation of hypahe -(Arthrospores)

Fungal spores are for reproduction,do not ensure resistance to

environmental conditions


24/77

Asexual Spores

Conidiospores

Chlamydospores

Sporangiospores Blastospores

Arthrospore


25/77

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

Most of the common household molds & mildewsare conidial fungi


26/77


27/77

Aspergillus sp.


28/77


29/77

Asexual spores ( cont)

Blastospores

A bud coming off the parent cell

Candida albicans


30/77

Chlamydospore

Formed within hyphae

Thick-walled spore

The chlamydospore is a method of producing

a substantial resting spore very quickly.

Nutrient is shunted from adjacent cells into apreferred 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 Candida albicans


31/77

Asexual spores

Sporangiospores

Hundreds formed within a sac (sporangium)

at the end of an aerial hypha

Rhizopus spp.

Mucor spp

Absidia spp


32/77

Spora-spora aseksual


33/77

Sporangiospore

1.Mucor

2.Rhizopus

3.Absidia

Cunninghamella


34/77

1.Mucor2.Rhizopus

3.Absidia


35/77

Cunninghamella


36/77

(1).arthrospore

(2).chlamydospor(3).phialospore


37/77


38/77


39/77


40/77

SEXUAL Spores

1. Zygospore

2. Ascospore

3. Basidiospore

4. Oospore

F l f


41/77

Fungi-Taxonomic classificationis based on sexual spores

SEXUAL SPORE CLASS

Zygospore----------ZygomycetesBasidiospore--------Basidiomycetes

Ascospore----------Ascomycetes

None/Unknown---- Deuteromycetes(Fungi Imperfecti)


42/77

Ascomycetes

Asexual phase- Conidiospores (Penicillium and Aspergillus)

budding yeast

Sexual phase (morels, lichens )


43/77

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 asagents for biological control of insects


44/77

Basidiomycetes

Basidiospore

Examples: boletes, puffballs,smuts,

stinkhorns and tooth fungi


45/77

MYCOSES

Superficial ( skin, hair, cornea)

Cutaneous ( Dermatophytosis ) Subcutaneous

True systemic (endemic)

Opportunistic


46/77

Laboratory to diagnosis of fungal

infection

Specimen collection and transport

Specimen processing

Direct examination

Selection and inoculation of culture media

Identification


47/77


must be material from the actual

infection site

must be carefully the contamination must be established for the best

chance of recovery of causativemicroorganisms (optimal times)

S i ll i d


48/77


( 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


49/77

Sampling

In superficial mycoses the scales or infected hairsmay be stored into small sterile glass Petri

dishes.

Infected nail or skin scrapings are taken from

the deeper parts with a blunt scalpel.

Specimens from the mucous membranes orfrom orifices should be collected with dry

swabs or preferably swabs soaked in

Sabourauds broth.


50/77

For the diagnosis of bronchopulmonary

infection morning sputum should be collected ina sterile container.

For systemic mycosis, pus swab from an ulceror aspiration from unruptured abscess, orbiopsy during surgical operation are collectedby strict aseptic technique.

For urinary tract infection, mid-stream urinesamples are collected into a wide mouth sterilecontainer.


51/77

For cerebrospinal infections, a lumbarpuncture should de performed to

collect CSF into sterile test tubes.

For Pleural and Peritoneal Effusions, a

sample is collected by needleaspiration into sterile container.


52/77


53/77

Specimen processing

specimen should be examined as soon as

possible

direct examination :

KOH mount

Calcofluor white

India ink culture media


54/77

Direct Examination


55/77

S l ti d i l ti f lt


56/77

Selection and inoculation of culture

media

Culture media for recovery of fungi from

clinical specimens usually used is PDA,

SDA orCorn Meal Agar.

The recovery rate may be somewhat

enhanced by using a variety of isolation

media, storage, incubator time and temp.


57/77

If the specimens are contaminated e.g. sputum,

incorporate antibiotics such as chloramphenicol

(0.5 g/l) in the media used for isolation.

Cycloheximide can also be incorporated for the

isolation of dermatophytes in order to get rid of

saprophytic fungi

The pathological material is spread upon the

surface of agar slopes. The fragments of skin,

hair or nail are planted with a firm straightpointed wire. Incubate slopes at temperature up

to 30oC


58/77

I iti l b ti


59/77

Initial observations

in the study of fungus isolates

1.Appearance of the growth

2. Rate of growth

3. Colony pigmentationn (Recto & Verso)

4. Growth on media containing antifungal

agents

5.Dimorphic fungi

Initial obser ations


60/77



1.Appearance of the growth

- surface and reverse surface of colonywere observed

- delicate or hairlike hyphae2. Rate of growth

- saprophytes : 3-5 days

- dimorphic fungi : 10 days or more- dermatophytes : 14 days or more



61/77


3. Colony pigmentation

4. Growth on media containing antifungal agents

- most strains of the dimorphic fungi can grow

- most strains of the rapidly growing saprophytes areinhibited

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)


62/77

Recto Verso


63/77

Microscopic Examination:

A Needle Mount is made as soon asspore formation is sufficiently advanced atthe center of the colony.

Place a drop of lactophenol cotton blue onthe glass surface.

With a nickel-chrome needle, pick-up a bit

of the mycelium and put it directly to thedrop of stain.

Cover it with a cover-slip and examineunder the microscope.


64/77


65/77

Histopathological Diagnosis

To establish the diagnosis of a fungus disease,

identification should be made by a combination

of mycologic and histopathologic study.

Because of size, characteristic morphology and

histochemical composition, fungi can be studied

satisfacorily in tissues.


66/77

Although many fungi can be seen with

haematoxylin and eosin stain (H&E), some arenot stained by this method.

Special stains for fungi are of great help in

reaching the etiologic agent. These stains are

mainly:

Periodic acid-Schiff stain (PAS).

Gomori methenamine Silver stain (GMS).

Mayers mucicarmine stain. Gridley fungal stain.


67/77

Serological Diagnosis

Serological diagnosis of mycoses usuallylacks complete specificity because some ofthe pathogenic fungi have common

antigens. Fractional separation of the active

antigenic components of a fungus has notbeen achieved with complete success.

However, serologic techniques are usefulin reaching a presumptive diagnosis.

Th th d i l d


68/77

These methods may include:

Double Diffusion method.

Counter-immuno electrophoresis.

Latex agglutination.

Indirect Immunofluorescence.

Indirect haemagglutination. ELISA.


69/77

Experimental Animal infection

Experimental animal inoculation is sometimesuseful for the isolation of the causative fungus

especially in deep mycoses.

White mouse - Histoplasmosis , Cryptococcosis.

Hamsterfor Blastomycosis

Albino Rabbit for Candidosis.

Guinea-pig for experimantal infections with zoophilic

Dermatophytes.


70/77

TYPES OF FUNGAL

INFECTION


71/77

Superficial Fungal Infections

DERMATOPHYTES.akaTinea

YEASTS

-Pityrosporum.-Candida sp.


72/77

TINEA Infections

T.Corporis- ringworm of body

T.Cruris- groin

T.Pedis- foot

T.Unguium- nail

T.Capitis - scalp


73/77

Yeasts

Pityrosporum & Candida.

Ordinarily commensals.

Can become pathogens underfavourable conditions.


74/77

Candidal Intertrigo


75/77

Pityriasis Versicolor

hypopigmented


76/77

T.Pedis


77/77

13.Introduction to Mycology

Documents

Transcript of 13.Introduction to Mycology