CAUSES OF INFECTION

Question 1

what agents cause infection?

Answer 1

Viruses
Bacteria
Fungi
Parasites 
Prions

Question 2

what factors will allow infection to occur?

Answer 2

Barriers to infection

Environment

Question 3

what are viruses?

Answer 3

Smaller than cellular organisms
Metabolically inert, Simple structure
Need living host cells to replicate

Question 4

what do viruses infect?

Answer 4

animals, plants and bacteria (bacteriophages)

Question 5

what are the 3 major components of a virus?

Answer 5

genetic material- either DNA or RNA; protein coat; lipid envelope which is derived from the host cell

Question 6

what do viruses contain?

Answer 6

genetic material but no organelles

Question 7

what do viruses rely on to reproduce?

Answer 7

their host’s organelles/ systems

Question 8

how do viruses act?

Answer 8

They use surface protein(s) to bind to a cell, insert their genetic material into it

Question 9

how long do viruses infect host cells for?

Answer 9

fo differing lengths of time

Question 10

give examples of viruses

Answer 10

chickenpox virus
rhinovirus
hepatitis C virus

Question 11

how long does the chickenpox virus act for?

Answer 11

can lay dormant for decades, emerging to cause shingles

Question 12

how long does the rhinovirus act for?

Answer 12

infects hosts for days, causing a cold

Question 13

how long does the hepatitis C virus act for?

Answer 13

causes chronic liver infection over years

Question 14

do viruses differ in the severity of disease?

Answer 14

yes

Question 15

what are severe viruses?

Answer 15

Ebola

SARS

Question 16

what are variable viruses?

Answer 16

Flu - different strains of influenza virus cause differing severity

Question 17

what are mild viruses?

Answer 17

Rhinovirus
Herpes simplex (cold sore or genital sores)

Question 18

what is bacteria?

Answer 18

Unicellular organisms
Reproduce asexually
Some move using flagella and attach via fimbriae

Question 19

what does bacteria contain?

Answer 19

cell membrane
cell wall
no nucleus-genetic material is DNA but no bound by membrane

Question 20

how is bacteria classified?

Answer 20

According to shape

According to ability of cell wall to take up stain

Question 21

what are the different shapes of bacteria?

Answer 21

round- cocci
rods- bacilli
spiral

Question 22

what are the different classifications that bacteria can take up stains?

Answer 22

gram positive

gram negative

Question 23

what does the type of cell wall help determine?

Answer 23

structural strength of cell, and how well it can survive in the environment or in
dry conditions

Question 24

what colour does gram negative stain?

Answer 24

stains pink

Question 25

what colour does gram positive stain?

Answer 25

stains purple

Question 26

give examples of bacterial diseases

Answer 26

Meningococcal sepsis Bacterial endocarditis Cellulitis Streptococcal throat infection

Question 27

what is fungi?

Answer 27

Kingdom of their own | Eukaryotes

Question 28

what do fungi contain?

Answer 28

Cell membrane, cell wall, nucleus and cytoplasmic structures

Question 29

how do fungi reproduce?

Answer 29

sexually or asexually

Question 30

give examples of fungi

Answer 30

yeasts moulds Diamorphic fungi (can switch between types)

Question 31

what are the different types of fungal infections?

Answer 31

mild or severe infections

Question 32

give examples of mild fungal infections

Answer 32

thrush, athletes foot, ringworm

Question 33

give examples of severe fungal infections

Answer 33

In the Immunocompromised (Cryptococcal meningitis in HIV patients, Invasive candida in ICU) Or Immune competent

Question 34

what are the 3 types of parasites?

Answer 34

ectoparasites endoparasites epiparasites

Question 35

what are ectoparasites?

Answer 35

live outside the body

Question 36

give an example of ectoparasites

Answer 36

fleas | ticks

Question 37

what are endoparasites?

Answer 37

live inside the body

Question 38

give examples of endoparasites

Answer 38

worms

Question 39

what are epiparasites?

Answer 39

a parasite which lives on another parasite

Question 40

give an example of epiparasites

Answer 40

malaria (mosquito)

Question 41

what are the 2 classes of human parasites?

Answer 41

Unicellular organisms- Protozoa | Worms- Helminths

Question 42

why do human parasites have complex life cycles?

Answer 42

Many human infections are “accidental” | Life cycle often involves other animals

Question 43

give an example of a parasitic disease

Answer 43

giardia

Question 44

what does giardia cause?

Answer 44

Cause bloody diarrhoea

Question 45

how is giardia caught?

Answer 45

Caught from drinking infected water

Question 46

how is giardia detected?

Answer 46

May be seen in stool under a light microsope | Cyst form aids survival + spread

Question 47

what is malaria?

Answer 47

One of the biggest killers worldwide Complex life cycle Reproduce in female anopheles mosquito

Question 48

what does malaria infect?

Answer 48

Infect human red blood cells

Question 49

what are the 4 different types of malarial parasites?

Answer 49

Falciparum is most severe Different types occur in different geographical areas with some overlap Resistance to treatment is now a problem in many areas

Question 50

what are worms?

Answer 50

Helminths

Question 51

what are the 3 different types of worms+ examples

Answer 51

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

Question 52

what shape are Cestodes?

Answer 52

Segmented, flat

Question 53

what shape are Trematodes?

Answer 53

Unsegmented, flat

Question 54

what shape are Nematodes?

Answer 54

Cylindrical, have digestive tract with lips, teeth and anus

Question 55

give an examples of cestodes?

Answer 55

tapeworms | Fish, pork, beef tapeworms

Question 56

what causes tapeworms?

Answer 56

Malabsorption Malnutrition in chronic disease Cysts in muscle or brain

Question 57

give an example of nematodes?

Answer 57

round worms

Question 58

what are tapeworms?

Answer 58

Biggest of helminth family | Huge burden of disease worldwide

Question 59

what causes tapeworms?

Answer 59

Diarhoea / malabsorption

Question 60

what are the different types of trematodes?

Answer 60

``` Flukes Lung flukes Liver flukes Pancreatic flukes Intestinal flukes Blood flukes- Schistosoma ```

Question 61

what are prions?

Answer 61

Smallest infective agents known | Proteinaceous Infectious particles

Question 62

what do prions lack?

Answer 62

Lack nucleic acid - not a ‘living organism’

Question 63

how are prions caused?

Answer 63

Proteins fold abnormally and accumulate, mainly in neural tissue

Question 64

are prions difficult to destroy?

Answer 64

yes

Question 65

give examples of prions disease

Answer 65

CJD BSE Scrapie Kuru

Question 66

what is CJD?

Answer 66

fatal, degenerative neurological disease

Question 67

how is CJD transmitted?

Answer 67

Transmitted through contaminated human growth hormone, surgical instruments and corneal grafts

Question 68

what does BSE occur in?

Answer 68

cattle

Question 69

what does Scrapie occur in?

Answer 69

sheep

Question 70

what are the different types of defence mechanism?

Answer 70

``` skin mucus membrane stomach acid commensal microflora immune system (innate+learnt) behaviour (good hygiene practise) ```