Microbiology 3

Question 1

How many different species of fungi is there ?

Answer 1

more than 100,000 species

Question 2

What is mcology ?

Answer 2

is the study of fungi

Question 3

What is fungi ?

Answer 3

are eukaryotic organisms that do not contain
chlorophyll, but have cell
walls, filamentous structures,
and produce spores

Question 4

How many species are known as to be pathogenic for man?

Answer 4

About 300 species are known

Question 5

What do the fungal species include ?

Answer 5

Moulds
Yeasts
Higher fungi

Question 6

What are the 2 forms of fungi ?

Answer 6

single and multicellular

Question 7

What are e.g of single and multicellular fungi?

Answer 7

Yeasts are single cell fungal forms

Most fungi form filaments called hyphae

Question 8

What is hyphae surrounded by ?

Answer 8

Hyphae are surrounded by a cell wall made of
polysaccharides (and may show cross walls (septa) )
A colony of hyphae is referred to as a mycelium

Question 9

What is candida?

Answer 9

• a yeast-like fungus commonly occuring on human skin, in the upper respiratory, alimentary & female genital tracts
• Some species e.g. Candida albicans – exist in yeast and hyphal stages (dimorphic)

Question 10

What are the 3 types of mycotic diseases ?

Answer 10

1. Hypersensitivity - an allergic
   reaction to molds and spores.
2. Poisoning due to fungal toxins
3. Infection

Question 11

What are the most common classification of fungal infections according to the tissues infected?

Answer 11

Superficial mycoses
Subcutaneous mycoses
Systemic mycoses
Opportunistic mycoses (infections with organisms of low viulence e.g. in immunosupressed)

Question 12

How can Systemic mycoses can occur?

Answer 12

can occur due to inhaled fungal spores or deep trauma. Examples include:
Aspergillus
Pneumocystis Carini

Question 13

What are the treatments of fungal disease ?

Answer 13

Because mammals and fungi 
   are both eukaryotic, the cellular 
   machinery is similar in both 
  Most substances which may 
   impair the invading fungus will    
   usually have serious side 
   effects on the host
 Targets include membrane 
   sterols or ergosterols

 Examples 
	Terbinafine (nail infections)
	Amphoteracin (oral or genital thrush)
	Nystatin (oral or genital thrush)
	Fluconazole  (genital thrush)

Question 14

What is a parasite ?

Answer 14

A parasite is an organism that obtains food and shelter from
another organism and derives benefits from this association

Question 15

What is the organism that harbors the parasite known as?

Answer 15

the host

Question 16

What is the host ?

Answer 16

The host in which the parasite lives its adult and sexual
stage is the definitive host whereas the host in which a
parasite lives as the larval stage is the intermediate host

Question 17

What is a vector \?

Answer 17

An organism (usually an insect) that is responsible for
transmitting the parasitic infection is known as the
vector

Question 18

What are classification of parasites ?

Answer 18

Protozoa e.g. Toxoplasma species
Helminths e.g. Toxocara species
Arthopods e.g. Ticks

Question 19

What is protozoa?

Answer 19

-Comprises a number of diverse groups of unicellular microorganisms

Question 20

What does the protozoa size ?

Answer 20

Measures from 5µm to 1mm

Question 21

Where do protozoa live?

Answer 21

Most live in water and are parasites of a range of species

All have mechanisms of locomotion via flagella or pseudopodia

Question 22

What can protozoa form ?

Answer 22

They can form cysts helping them to survive in the environment for a long time
They are divided into 4 groups based on motility

Question 23

What are groups of protozoa ?

Answer 23

Mastigophora
Giardia
Trichomonas

Sarcodina/Rhizopodia
Acanthamoeba
Entamoeba

Sporozoa
Plasmodium
Toxoplasma

Ciliata
Balantidium

Question 24

What is acanthamoeba?

Answer 24

Are free living amoebae (20 different species)
Found everywhere, most prevalent in soil, fresh water and other habitats
Can be an opportunistic or non-opportunistic pathogen
This genus causes 3 clinical syndromes:
Granulomatous amoebic encephalitis
Disseminated granulomatous amoebic disease (eg, skin, sinus, and pulmonary infections)
Amoebic keratitis (1-33 cases per million CL wearers)

Question 25

What is the acanthamoeba life cycle ?

Answer 25

Consist of 2 stages
An actively feeding stage referred to a trophozoite
A dormant cyst
Trophozoites feed on bacteria, yeast, algae and cells

Question 26

What are trophozoite feeding ?

Answer 26

Acanthamoeba feed on micro-organisms in bio-films.
Acanthamoeba detects prey items by chemotaxis
Prey items are usually bacteria

Question 27

Acanthamoeba keratitis

Answer 27

Early Disease: linear epitheliopathy, perineural infiltrates

Question 28

Acanthamoeba keratitis

Answer 28

Late Disease: ring infiltrates, anterior uveitis, hypopyon

Question 29

What is toxoplasma caused by ?

Answer 29

the protozoa, Toxoplasma gondii
Between 7-34% of people in the UK have been infected with T. gondii, however, the vast majority of these people will not have noticed any symptoms.

Question 30

What is bad about toxoplasmosis ?

Answer 30

toxoplasmosis can be a dangerous and potentially fatal disease e.g. toxoplasmosis encephalitis in immunocompromised patients
An infected pregnant woman can congenitally infect her unborn child

Question 31

What is the The life cycle of the parasite?

Answer 31

is complex, but can only be completed in cats (definitive host) that excrete resistant oocysts in their faeces

Question 32

What is the toxoplasma life cycle ?

Answer 32

Oocysts (eggs) can infect virtually all warm-blooded animals
Infection occurs either directly by ingesting substances contaminated with cat faeces or indirectly by ingesting undercooked infected meat of species which have themselves become infected from cats

The tachyzoite form is crescent shaped, 2-3 μm wide and 5-7 μm long, and is usually found in intracellular clusters of 8 to 32 parasites

Question 33

What is the helminths ?

Answer 33

The parasitic helminths of man belong to 3 groups:

• Nematodes (round worms)
• Cestodes (tapeworms)
• Trematodes (flukes)

Question 34

What is toxocara ?

Answer 34

Toxocara canis is a roundworm parasite of dogs and foxes

Eggs of these parasites can survive in the environment for many years

Question 35

what is. the toxocara life cycle ?

Answer 35

Humans (usually children) can acquire T. canis eggs by ingesting soil, by direct contact with dogs (usually puppies) or by consumption of uncooked or undercooked food contaminated with eggs, possibly transmitted by flies

Question 36

What are the symptoms of toxocara ?

Answer 36

Some infections may be asymptomatic, but there are a number of clinical syndromes:
Visceral toxocariasis —caused by the migration of larvae through the internal organs of humans and the resulting inflammatory reaction. May cause hepatosplenomegaly, fever, respiratory signs, pallor, skin lesions and neurological manifestations, e.g. convulsions
Ocular toxocariasis — migration of larva into the posterior segment of the eye, tends to occur in older children and young adults. Patients may present with decreased vision, red eye, or leukocoria (white appearance of the pupil)

Question 37

What is ochocera ?

Answer 37

Onchocerciasis (river blindness) is endemic within the river basins of West and Central Africa and is the most frequent ophthalmic worm infection (>1 million cases of blindness worldwide)
Humans are the definitive host
Black fly is the intermediate host which also acts as the vector for transmitting the disease
Ocular manifestations: keratitis, iridocyclitis, retinitis, optic atrophy