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Flashcards in CAUSES OF INFECTION Deck (70):
1

what agents cause infection?

Viruses
Bacteria
Fungi
Parasites
Prions

2

what factors will allow infection to occur?

Barriers to infection
Environment

3

what are viruses?

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

4

what do viruses infect?

animals, plants and bacteria (bacteriophages)

5

what are the 3 major components of a virus?

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

6

what do viruses contain?

genetic material but no organelles

7

what do viruses rely on to reproduce?

their host’s organelles/ systems

8

how do viruses act?

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

9

how long do viruses infect host cells for?

fo differing lengths of time

10

give examples of viruses

chickenpox virus
rhinovirus
hepatitis C virus

11

how long does the chickenpox virus act for?

can lay dormant for decades, emerging to cause shingles

12

how long does the rhinovirus act for?

infects hosts for days, causing a cold

13

how long does the hepatitis C virus act for?

causes chronic liver infection over years

14

do viruses differ in the severity of disease?

yes

15

what are severe viruses?

Ebola
SARS

16

what are variable viruses?

Flu - different strains of influenza virus cause differing severity

17

what are mild viruses?

Rhinovirus
Herpes simplex (cold sore or genital sores)

18

what is bacteria?

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

19

what does bacteria contain?

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

20

how is bacteria classified?

According to shape
According to ability of cell wall to take up stain

21

what are the different shapes of bacteria?

round- cocci
rods- bacilli
spiral

22

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

gram positive
gram negative

23

what does the type of cell wall help determine?

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

24

what colour does gram negative stain?

stains pink

25

what colour does gram positive stain?

stains purple

26

give examples of bacterial diseases

Meningococcal sepsis
Bacterial endocarditis
Cellulitis
Streptococcal throat infection

27

what is fungi?

Kingdom of their own
Eukaryotes

28

what do fungi contain?

Cell membrane, cell wall, nucleus and cytoplasmic structures

29

how do fungi reproduce?

sexually or asexually

30

give examples of fungi

yeasts
moulds
Diamorphic fungi (can switch between types)

31

what are the different types of fungal infections?

mild or severe infections

32

give examples of mild fungal infections

thrush, athletes foot, ringworm

33

give examples of severe fungal infections

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

34

what are the 3 types of parasites?

ectoparasites
endoparasites
epiparasites

35

what are ectoparasites?

live outside the body

36

give an example of ectoparasites

fleas
ticks

37

what are endoparasites?

live inside the body

38

give examples of endoparasites

worms

39

what are epiparasites?

a parasite which lives on another parasite

40

give an example of epiparasites

malaria (mosquito)

41

what are the 2 classes of human parasites?

Unicellular organisms- Protozoa
Worms- Helminths

42

why do human parasites have complex life cycles?

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

43

give an example of a parasitic disease

giardia

44

what does giardia cause?

Cause bloody diarrhoea

45

how is giardia caught?

Caught from drinking infected water

46

how is giardia detected?

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

47

what is malaria?

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

48

what does malaria infect?

Infect human red blood cells

49

what are the 4 different types of malarial parasites?

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

50

what are worms?

Helminths

51

what are the 3 different types of worms+ examples

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

52

what shape are Cestodes?

Segmented, flat

53

what shape are Trematodes?

Unsegmented, flat

54

what shape are Nematodes?

Cylindrical, have digestive tract with lips, teeth and anus

55

give an examples of cestodes?

tapeworms
Fish, pork, beef tapeworms

56

what causes tapeworms?

Malabsorption
Malnutrition in chronic disease
Cysts in muscle or brain

57

give an example of nematodes?

round worms

58

what are tapeworms?

Biggest of helminth family
Huge burden of disease worldwide

59

what causes tapeworms?

Diarhoea / malabsorption

60

what are the different types of trematodes?

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

61

what are prions?

Smallest infective agents known
Proteinaceous Infectious particles

62

what do prions lack?

Lack nucleic acid - not a ‘living organism’

63

how are prions caused?

Proteins fold abnormally and accumulate, mainly in neural tissue

64

are prions difficult to destroy?

yes

65

give examples of prions disease

CJD
BSE
Scrapie
Kuru

66

what is CJD?

fatal, degenerative neurological disease

67

how is CJD transmitted?

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

68

what does BSE occur in?

cattle

69

what does Scrapie occur in?

sheep

70

what are the different types of defence mechanism?

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