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Fundamentals Of Science > Principles of Infection 2 > Flashcards

Principles of Infection 2 Flashcards

1
Q

Steps to becoming unwell with an infection

A
  1. Transmission
  2. Infection
  3. Pathogenicity
  4. Virulence
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2
Q

what happens at the transmission step?

A

host has to acquire the organism

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3
Q

what happens at the infection step?

A

the organism has to reproduce inside the host

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4
Q

what happens at the pathogenicity step?

A

organism interacts with the host in a way that causes diseases

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5
Q

what happens at the virulence stage?

A

organism causes a disease of varying severity

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6
Q

example of air-borne spread

A

aerosols or droplets from cough etc

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7
Q

examples of person to person spread

A

direct e.g. skin infection, STDs

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8
Q

Examples of faceo-oral spread

A

most often via food/ water e.g. cholera

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9
Q

examples of consumption of infected material transmission

A

e.g. salmonella, tapeworm

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10
Q

example of vector-borne disease transmission

A

mosquitos spread malaria & zika infection

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11
Q

example of endogenous infection transmission

A

from movement of own microbiome e.g. colonic bacteria to urine

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12
Q

example of direct inoculation transmission

A

e.g. open fracture, bite form infected animal

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13
Q

how do microorganisms cause disease?

A

indirect damage by host immune response and direct damage by the pathogen

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14
Q

How does the host immune response cause indirect damage?

A
  • inflammation causes tissue damage & lost of normal function
  • systemic response to infection can cause organ failure and death
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15
Q

How does a pathogen cause direct damage?

A
  • viral reproduction causes cell lysis ( cell breakdown)
  • Bacteria secrete toxins causing cell damage
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16
Q

How do microorganisms evade the immune system?

A
  1. Adhere (stick) to the epithelium
  2. Invade epithelial cells / cross epithelial barrier
  3. Evade innate immune cells
  4. Evade adaptive immune cells and antibodies
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17
Q

define virulence factors:

A

components or structure of microorganisms that helps in establishment of disease or infection (essentially to assist microorganism to colonise)

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18
Q

virulence factors include factors that allow microorganisms to:

A
  • Adhere to and invade host tissues
  • Evade host defences
  • Proliferate in the host
  • Cause damage
  • Produce toxins
  • host- pathogen interaction
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19
Q

tiny hairs on bacteria are called?

A

pili

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20
Q

Define adhesins

A

(on bacteria that) allows them to stick onto epithelial cells & stops them from being swept away

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21
Q

Define adhesins and pili

A

pili- tiny hairs (on bacteria that) and adhesins allow them to stick onto epithelial cells & stops them from being swept away

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22
Q

Some bacteria secrete enzymes which do what?

A

degrade the host molecules by attacking the epithelial barrier (e.g. breaking down tight junctions)

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23
Q

secretion of enzymes allows bacteria/ viruses to?

A

get past the barrier and then sit in the interstitial/ extracellular fluid however can get into epithelial cells or immune cells (e.g. tuberculosis)

24
Q

Once bacteria/virus has invaded the cell, they will do what?

A

set of signalling molecules that will propagate this and make this process worse

25
Q

Steps to adherence and invasion

A
  • Bacteria has anatomical structure (pili and adhesins)
  • Some bacteria secrete enzymes, attacking the barrier
  • Can however get into epithelial or immune cells
  • once invaded it will set of signalling molecules
26
Q

Examples of evade host defences in bacteria

A

capsule, cell wall and toxins

27
Q

Examples of evade host defences in viruses

A

antigenic drift, antigenic shift

28
Q

Function of capsule in bacteria

A

-protects bacteria from host immune response and antibiotics

29
Q

‘frustrated phagocytosis’ enhances?

A

the inflammatory response

30
Q

define frustrated phagocytosis

A

occurs when phagocytic cells are exposed to an opsonised surface and spread as if trying to engulf it

31
Q

Function of cell wall in bacteria

A
  • contains endotoxins - excreted after cell death & lysis
  • Activate a pathway of events weakening host (septic shock)
32
Q

define antigenic drift

A

small changes in viral antigens due to point mutations in genes

33
Q

define antigenic shift

A

Major changes in vial antigens due to gene reassortment

34
Q

virulence factors are determined how?

A

genetically

35
Q

Horizontal gene transfer enables?

A

bacteria to respond and adapt to their environment rapidly by acquiring large DNA sequences from another bacterium in a single transfer

36
Q

Horizontal gene transfer therefore means bacteria can?

A

share antibiotic resistance genes

37
Q

genes disseminated by horizontal transfer allows?

A

bacteria to share common pathogenic mechanisms and antibiotics resistance

38
Q

Strep A is transmitted how?

A

person- person spread, air- borne

39
Q

Infection by Streptococcus A is what type of bacteria? shape? oxygen conditions?

A

Gram positive
Cocci shape
Aerobe

40
Q

Pharyngitis also known as

A

sore throat

41
Q

scarlet fever also known as?

A

rash

42
Q

How does sore throat (pharyngitis) cause indirect damage by host immune response?

A

Bacteria invade throat cells
- immune system fights bacteria causing inflammation

43
Q

How does scarlet fever cause direct damage by the pathogen?

A

Bacteria in the throat make a toxin that enters the body and causes a skin rash

44
Q

How does Invasive group A strep disease by direct damage by the pathogen?

A

Bacteria evade the immune system and spread to a normally sterile body site- toxin causes shock and multiorgan failure

45
Q

Virulence of sore throat, rash, Strep A?

A

Sore throat: mild- very common
Rash: moderate - less common
Strep A : severe - very rare

46
Q

what causes influenza?

A

viruses: several types cause infection in humans : influenza A, B & C

47
Q

How is Influenza highly transmissible?

A

air- borne, person to person direct & indirect contact, can also come from animals and birds

48
Q

How does Influenza infect?

A

viruses enter cells of respiratory tract and proliferate

49
Q

Pathogenesis of Influenza via direct damage

A

-Viruses directly damage respiratory cells by lysis during reproduction

50
Q

Pathogenesis of Influenza via indirect damage

A

-Viruses cause indirect damage by triggering an immune response which causes damage and symptoms

51
Q

Viiruses make a lot of ‘mistakes’ during replication, by creating?

A

new strains

52
Q

SARS- CoV-2 is what type of virus

A

RNA virus

53
Q

Why do RNA viruses have a high mutation rate?

A

RNA viruses dont have proof reading mechanisms to correct mistakes

54
Q

define a variant

A

where the viral genome contains one or more mutations

55
Q

List ways some variants confer advantages on the virus

A
  • Increase transmissibility

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