Lab no 5Lab no 5

Definition:

Fungi are eukaryotic organisms and

include the yeasts, fleshy fungi & molds

which include dimorphic fungi.

Yeasts are microscopic, unicellular fungi;

molds are multinucleated, filamentous

fungi and the fleshy fungi include

mushrooms.

All fungi are chemoheterotrophs, requiring organic compounds as an energy and carbon source. They obtain nutrients by absorbing them from their environment.

Most of them survive by decaying organic material and are termed saprophytes. Some are parasitic, getting their nutrients from living plants or animals.

The study of fungi is termed mycology and the diseases caused by fungi are

called mycotic infections or mycoses.

Uses of fungi

In general, fungi are beneficial to humans. They are involved in :

1. The decay of dead plants and animals (resulting in the recycling of nutrients in nature).

2. The manufacturing of various industrial and food products.

3. the production of many common antibiotics,

4. and may be eaten themselves for food.

MouldsYeast

Dimorphic

FungiFungi

Fungi

Classification of fungi

.

It is classified according to morphology into:

1. Yeasts:1. Yeasts: oval or round cells that reproduce by

budding e.g: Cryptococcus

neoformans . Some yeasts produce chains of

elongated budding cells (Pseudohyphae)

e.g: Candida albicans.

2. 2. Filamentous fungi Filamentous fungi (Moulds):(Moulds):

• Grow as branching filaments (hyphae).

• Reproduce by spores

e.g.: Aspergillus, Penicillium and rhizopus species

33. . Dimorphic fungi:Dimorphic fungi: They grow either in tissue or in

culture at 37 oC in yeast form but when cultures are incubated at 22 oC they appear in mould forms.

e.g.: histoplasma and blastomyces.

Specific Cultivation Medium

Sabaroud’s Dextrose Agar: It has acidic PH. It contains relatively high concentrations of sugars

e.g; dextrose and maltose. enhanced SDA with the addition of cycloheximide,

streptomycin, and penicillin to produce an excellent medium for the primary isolation of fungi.

Culture of pathogenic yeasts are incubated at 37 oC

Candida albicans

it is an oval budding yeast which produces pseudohyphea.

It is a normal inhabitant of the mouth, vagina and intestine .

It may predominate and cause super infection. It causes oral or vaginal thrush .

Candida albicans..

Laboratory diagnosis:1. Direct microscopic examination : Gram stain that show large gram positive

budding cells with pseudohyphea.2. Culture on sabouraud’s dextrose agar :

large cream colonies with yeasty odour which can be identified by Gram stain

Filamentous Fungi

Structure of Filamentous Fungi:Structure of Filamentous Fungi:Structure of Filamentous Fungi:Structure of Filamentous Fungi:

1. Hyphae:• It is a tube or filament that could be septate or non septate

Filamentous Fungi ,cont..

2 .Mycelium:

Macroscopic collection of branching hyphae

Divided into:

* Vegetative: diffuses into the medium to absorb nutrients.

* Aerial: projects above the substrate and contains spores.

Filamentous Fungi ,cont..

3. Spores:• More resistant to unfavorable environmental condition.• reproductive elements produced on the aerial mycelium.• produced by asexual cell division or as a result of sexual reproduction.

Filamentous Fungi ,cont..

• Asexual spores could be classified according to their relation to the parent hyphae into:

*Conidiospores(never enclosed in a

sac)Eg. Aspergillus, Penicillium

Sporangiospores

(formed inside a sac

“sporangium)”Eg. Mucor sp.

Filamentous Fungi

AspergillusAspergillus

PenicilliumPenicillium

Rhizopus

Parasitology

Important definitions Medical parasitology: “the study and

medical implications of parasites that infect humans”

A parasite: “a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”. Parasites may be simple unicellular protozoa or complex multicellular metazoa

Protozoa: unicellular organisms, e.g. Plasmodium (malaria)

Metazoa: multicellular organisms, e.g. helminths (worms) and arthropods (ticks, lice)

Important definitions

An endoparasite: “a parasite that lives within another living organism” – e.g. malaria, Giardia

An ectoparasite: “a parasite that lives on the external surface of another living organism” – e.g. lice, ticks

Taxonomic classification of parasitic organisms

Parasites are classified into 2 sub-kingdoms: protozoa (unicellular) and metazoa (multicellular)

Protozoan (unicellular) parasites are classified according to morphology and means of locomotion.

Metazoa (multicellular) include the worms (helminths) and arthropoda (posses an external skeleton) e.g. ticks, lice

Note that the genus starts with a capital letter and the species is always written in italics, e.g. Plasmodium falciparum, Giardia lamblia

Sub kingdom

PhylumSub-phylumGenus- examples

Species- examples

ProtozoaSarcomastig-ophorafurther divided into

Sarcodina(Rizopoda)- - move by pseudopodia

EntamoebaE. histolytica

Mastigophoramove by flagella

Giardia (GI)Trichomonas (GU)Trypanosoma Leishmania (Blood and tissue)

G. intestinalisT. VaginalisT. gambiense, T. rhodesiense Leishmania sp.

Apicomplexa (sporozoa)no organelle ofLocomotion

Plasmodium

Toxoplasma

P. falciparum, P. vivax, P. malariae, P. Ovale

T.gondii.

Ciliophoramove by cillia

BalantidiumB. coli

MicrosporaSpore-forming

Enterocyto-zoaE. bienusi

Taxonomic classification of

protozoa

Entamaeba trophozoite

Giardia trophozoite

Trichomonas vaginalis trophozoite

Leishmania parasite

Trypanosoma trypomastigote

Plasmodium rings

Plasmodium gametocyte

Balantidium coli cyst

Sub kingdo

m

PhylumClassGenus – examples

Metazoa

NematodesRound worms; appear round in cross section, they have body cavities, a straight alimentary canal and an anus

Ascaris (roundworm)Trichuris (whipworm)Ancylostoma(hookworm)Necator (hookworm)Enterobius (pinworm or threadworm)Strongyloides

PlatyhelminthesFlat worms; dorsoventrally flattened, no body cavity and, if present, the alimentary canal is blind ending

CestodesAdult tapeworms are found in the intestine of their hostThey have a head (scolex) with sucking organs, a segmented body but no alimentary canalEach body segment is hermaphrodite

Taenia (tapeworm)

TrematodesNon-segmented, usually leaf-shaped, with two suckers but no distinct headThey have an alimentary canal and are usually hermaphrodite and leaf shapedSchistosomes are the exception. They are thread-like, and have separate sexes

Fasciolopsis (liver fluke)Schistosoma (not leaf shaped!)

Taxonomic classificatio

n of helminths

Roundworms (Nematodes)

Roundworms are long and cylindrical and are tapered at each end. They possess complete digestive tracts and are dioecious (separate male and female sexes).

The male worms are slightly smaller than the female worms.

In some cases, a roundworm may only have a single host. In other cases, multiple hosts are required for the maturation of the worm.

The medically relevant members of this phylum are divided into two groups: those that infect in the egg stage and those that infect via the larval stage.

T.S. in ascaris body

Ascaris egg

Trichuris egg

Trichuris male and female

Trichenella spiralis in skeletal muscle

Ancylystoma male

Ancylystoma female

Flatworms (Platyhelminths)They are considered monoecious (hermaphroditic).. a. Cestodes (Tapeworms): are flat, segmented,

intestinal parasites that contain two distinct regions: a scolex (a small attachment organ that contains suckers and hooks for attachment) and a proglottid, which irradiates from the neck and grows continuously. It is within the proglottid that both the male and female reproductive parts. As the proglottid grows away from the scolex, the eggs mature. The mature, fragmented proglottid containing thousands of eggs has the capacity to detach from the rest of the worm and be carried out in the feces. If the eggs are picked up by an intermediate host, the life cycle begins again.

Taenia eggs

Taenia solium scolex

Taenia proglottid

Flatworms (Platyhelminths)

b. Trematodes(Flukes): Flukes have flat, leaf shaped bodies that contains both oral and ventral suckers that allow for attachment to the host.

They also contain a cuticle that is an outer covering used to absorb nutrients for the worm. Flukes are often classified based on the tissue they inhabit.

Fasciola hepatica worm

Scistosoma meracidium

Scistosoma male and female in coupla

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