1
Q
What is an infection?
A
The invasion and multiplication of microorganisms that are not normally present on or within the body
2
Q
What is an infectious disease?
A
An infection caused by “pathogenic microorganisms” that result in a collection of signs and symptoms
3
Q
What is colonisation?
A
The presence and multiplication of microorganisms in or on a host that does not result in tissue invasion or damage
4
Q
What is a pathogen?
A
A microorganism that has the capacity to cause disease
5
Q
What is virulence?
A
A measure of pathogenicity, or the likelihood of causing disease
6
Q
What is a virulence factor?
A
A bacterial factor or strategy that contribures to virulence
7
Q
Explain the balance between health and disease
A
- health is a balance between host defence and pathogen exposure
- host defence > Pathogen exposure = healthy
- Host Defence < Pathogen exposure = disease
8
Q
What is a principle pathogen?
A
A pathogen that regularly causes disease
9
Q
What is an example of a principle pathogen?
A
Streptococcus pneumonia
10
Q
What is an opportunistic pathogen?
A
A pathogen that rarely causes disease
11
Q
What is an example of an opportunistic pathogen?
A
Pseudomonas aeruginosis
12
Q
Why is there a lower pathogen exposure in developed countries?
A
- clean water
- improved sanitisation
- low density population
- proper food handling
- vaccination
13
Q
Why is there higher pathogenic exposure in developing countries
A
- poor water
- low sanitation
- high density of living
- improper handling of food
14
Q
What are the major requirements for successful infection of human hosts by pathogenic bacteria?
A
- recognition of host receptor
- adhesion
- evade host immunity, acquire essential nutrients
- growth
- dissemination or transmission to another host
- invasion (If disseminated), shedding (if transmitted to another host)
15
Q
How can Microorganisms enter the body?
A
- Mouth
- Urinogenital Tract
- Conjunctive
- Scratch, Injury
16
Q
Once entered, where do microorganisms shed out>
A
- mouth
- conjunctive
- urinogenital tract
- anus
17
Q
What does a pathogen need to be able to do when leaving to be successful?
A
- transmit to a new host
18
Q
What are the routes of transmission?
A
- direct contact
- Indirect contact
- Droplet transmission
- Hands
- Vector-borne
- Nosocomial
19
Q
What are the 3 types of innate immune system defences?
A
- Anatomical barriers
- Humoral barriers
- Cellular barriers
20
Q
Give and examples of an anatomical barrier
A
- skin
21
Q
Give an examples on humoral barriers
A
- recruitment of phagocytic cells
22
Q
Give an example of cellular barriers
A
- Neutrophils, macrophages, dendritic cells
23
Q
Explain features of the skin as a physical and chemical barrier
A
- relatively impermeable
- dry
- acidic pH (4-5.5)
- Temperature <37c
- Sloughing of cells
- Fatty acids
24
Q
What are examples of respiratory barriers?
A
- upper respiratory tract (nasal hairs trap microorganisms, cough response expels microorganisms, Throat has normal microbiota)
- Lower respiratory tract (lined with mucus layer produced by goblet cells, ciliated cells propel mucus upwards, mucus traps bacteria and secretory IgA binds to bacterial antigens)
25
What are host defences in the urinary tract?
- Mechanical processes (sphincter muscles prevent entry into bladder, urination flushes out bacteria)
26
What are the defence mechanisms of the GI tract?
- Mucus Membranes line GIT
- Stomach is acidic (pH2)
- Small intestine has bile salts and peristalsis
- Large intestine has slow flow rate and half volume colon
27
What is the role of normal flora of the GUT in host defence
- Compete with pathogens for nutrients
- Exclude pathogens by inhabiting specific sites
- Produce antibacterial agents
- Metabolic processes change pH
- Produce toxic metabolites
- Contribute to a range of biochemical and metabolic pathways (e.g. vitamin synthesis, organic acid production)
28
What happens when pathogens break through host physical and chemical defence mechanisms?
They encounter the body's immune defences
29
What are the 2 types of immune responses?
Innate and specific (adaptive) immune responses
30
Which response is antigen independent and which is antigen dependent?
```
Innate = independent
Adaptive = dependent
```
31
Which immune system results in immunological memory?
Specific immune responses
32
How are microbial cells recognised by the innate immune system?
- Microbial cells has Pathogen-associated molecular patterns (PAMPs) which are recognised by pattern recognition receptors (PRRs)
33
What are examples of PRRs?
- Toll-like receptors (TLRs)
- Nod-like receptors (NLRs)
- Rig-like receptors (RLR's)
34
After recognition, what do TLR's do?
- activate macrophage and dendritic cells
- secrete pro-inflammatory mediators
- initiate adaptive immune response
35
Once inside the host, how do bacteria overcome a host's defence mechanism?
- They possess a bacterial armament
36
What is the general process of bacteria virulence which leads to disease
- Exposure
- adherence
- invasion
- colonisation and growth
- Toxicity or invasiveness
- tissue damage, disease
37
During early infection, how do bacteria interact and bind to a host cell surface
- Pili or fimbrae, present on all gram negative bacteria cells allow binding
- Afimbral adhesions, bacteria binds directly to receptors on the host cell surface
38
Give examples of afimbral adhesion
- Sticky out capsule (spectococcus mutans produces dextran polysaccharide which allows binding to tooth surface)
- Adherence proteins (M proteins on surface of streptococcus pyogenes)
- Lipoteichoic acid (facilitates binding to a respiratory mucosal receptor of Strep pyogenes)
39
True of False: bacteria pathogens have specific tissue specificity when binding
True
40
In microorganisms, what is motility and how does it work?
- When bacteria can move to mucosal surfaces via a flagella
41
In microorganisms, what is chemotaxis?
- Bacteria can move to mucosal surface as a result of chemotactic responses
42
What is the main essential growth requirement required to survive for bacteria?
- Iron
43
How do bacteria acquire iron?
- Siderophore production
44
How does siderophore production work?
- Activated in conditions if iron limitation
- Creates a specific ferric iron chelating molecules that captures iron from their host
- Binds host iron with high affinity
- Siderophore-iron complex taken up by bacterium
45
Explain bacterial survival in regards to invasion and intracellular residence
- Some pathogens enter host cells that are not naturally phagocytic
- Receptors are attached on host cell surface
- This leads to changes in host cell cytoskeleton as well as actin re-arrangement (creates pseudopod-like structures which leads to engulfment)
- Invasion protect the pathogen from the immune response and allows it to continue to multiply
46
What is the purpose of bacterial capsules in regards to evasion of host defences?
- Prevents bacterial phagocytosis
47
What is secretory IgA protease?
- An antibody that binds to mucin via Fc portion of antibody and to bacterial antigen through Ag binding sites (facilitates bacterial removal from host)
48
What is bacterial strategy for survival against sIgA
- Production of SiGA proteases which destroys sIgA
49
What are virulence factors that damage the host?
- Endotoxin (embedded in gram negative outer membrane and creates an inflammatory response)
- Exotoxins (excrete out of cell)
50
What are 2 types of bacteria with extracellular virulence factors?
- Streptococcus pyogenes
| - Staphylococcus aureus
51
True of false: The pathology induced in a host must relate to either the host response or the pathogen but not both
False: can be either or both
52
What are 3 infectious disease outcomes?
- Short term infection and recovery
- Chronic infection
- Death
BABS3081
flashcards
Decks in class (18)
# Cards
-
Microbial Pathogenesis Overview52
-
Pathogenesis of Streptococci24
-
Staphylococcus27
-
Eschericia Coli and UTI's21
-
Enteropathogenic and Enterohaemorrhagic E.coli25
-
Enterotoxigenic and Enteroaggregative E.coli24
-
Shigella and Shigellosis17
-
Mid Sem - Important questions72
-
Salmonella overview11
-
Campylobacter Overview8
-
Vibrio Cholerae8
-
Anaerobic infections (clostridium)12
-
Meningitis8
-
Gonorrhoea and chlamydia trachomatis7
-
Pseudomonas11
-
Mycobacteria8
-
Helicobacter Pylori7
-
Pneumonia (gram positive cocci)9
