Pathogens and the host Flashcards Preview

Principles of dizzees > Pathogens and the host > Flashcards

Flashcards in Pathogens and the host Deck (30):
1

What is the difference between a pathogen and a commensal?

Pathogens will cause disease whereas commensals are organisms that exist as part of the normal flora and do not cause harm

2

Define pathogenicity.

The capacity of a micro-organism to cause an infection

3

What 2 factors are essential in determining a virus's pathogenicity?

Virulence
Infectivity

4

What does infectivity mean?

The ability of a pathogen to become established on or within a host

5

What structural feature of a bacterium increases it's infectivity, and why?

Fimbriae

Allows attachment to cell

6

Helicobacter pylori infects in the stomach. What feature of it increases it's infectivity?

It has acid resistance

Allows it to survive

7

What is virulence?

The capacity of a pathogen to cause harmful effects once established on or within a cell

8

Virulence factors determine how harmful a pathogen is.
List the virulence factors.

Invasiveness
Toxin production
Evasion of immune system

9

Virulence factors are specific to strains, not species.
Give an example of a type of bacteria, who's strains vary greatly in their virulence.

E. Coli

Some strains are completely harmless and live in gut normally

Some are not so good

10

What is the difference between infection and colonisation?

Infection will cause symptoms to show

Colonisation will not cause symptoms to show

11

Define colonisation.

When a pathogen grows at a site of infection, without causing symptoms to show

12

Using fancy words, a patient who's body was the host to colonisation of bacteria would be what?

Asymptomatic

13

What is the difference between an acute infection, and a chronic infection?

Acute = short term
Chronic = long term

14

What is a sub-clinical infection?

Asymptomatic
Occult

No apparent symptoms

15

In general, what are the differences between the symptoms of a viral infection, and those of a bacterial infection?

Viral infections are systemic, and often affect more than one system at once. Affected systems/areas tend to be itchy and/or burning, and few are painful.

Bacterial infections often involve localised pain, swelling, redness and burning in a specific area, not a system.

16

Describe the 3 types of toxins.

Exotoxins - released by the pathogen

Enterotoxins - type of exotoxin - act in GI tract

Endotoxins - structurally part of gram negative cell wall

17

Describe the structure of an endotoxin.

Lipopolysaccharide

Composed of lipid A, an oligosaccharide core and a specific polysaccharide chain

18

Although bacterium can cause harmful effects using toxins, how else can infection of bacteria cause harm?

The host's response

(hypersensitivity and all that stuff)

19

What is the difference between a primary and a secondary infection?

Primary - Root cause of infection
Secondary - caused/allowed due to another infection

20

When a latent virus goes into dormancy, how does it exist?

The virus is latent in the nucleus

21

What is opsonisation?

Covering of pathogen in antibodies or compliment proteins

Phagocytic cells have receptors for both

Efficiency for phagocytosis is greatly improved

22

What effect do compliment proteins have on the immune system?

Opsonise

Breakdown of Gram negative organisms

Compliment cascade signals polymorphs (neutrophils, eosinophils, basophils) to come to site of infection

23

Humoral (extra-cellular) immunity MOSTLY deals with what type of infection; viral or bacterial? Acute or chronic?

Bacterial
Acute

24

Cell mediated immunity MAINLY combats what type of infection?

Viral infection

(some bacterial and some fungi)

25

What are the 3 types of vaccine?

Live attenuated

Killed (inactivated)

Toxoid

26

What is a toxoid vaccine?

Toxin treated with formalin

Antigens remain but no toxic activity

27

Bacterium X produces toxin Q

You are given a toxoid vaccination and all is good

You are exposed to bacterium X again. Describe what will happen.

Bacterium X is still able to colonise

However it can not infect you

Sub-clinical infection as no symptoms

Toxoid vaccinations are against the toxin, not the organism

28

Why are live attenuated vaccinations difficult to administer in developing nations?

Must be refrigerated until they are given

29

There is a risk with live-attenuating vaccinations that killed vaccinations do not have. What is this?

Risk of pathogen reverting back to 'wild-type'

30

What are the main sites of viral entry?

Conjuctiva
Respiratory tract
Alimentary tract
Urinogenital tract
Skin
Capillaries (via a vector)