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BABS3081 > Microbial Pathogenesis Overview > Flashcards

Microbial Pathogenesis Overview Flashcards

1
Q

What is an infection?

A

The invasion and multiplication of microorganisms that are not normally present on or within the body

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2
Q

What is an infectious disease?

A

An infection caused by “pathogenic microorganisms” that result in a collection of signs and symptoms

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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

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4
Q

What is a pathogen?

A

A microorganism that has the capacity to cause disease

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5
Q

What is virulence?

A

A measure of pathogenicity, or the likelihood of causing disease

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6
Q

What is a virulence factor?

A

A bacterial factor or strategy that contribures to virulence

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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
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8
Q

What is a principle pathogen?

A

A pathogen that regularly causes disease

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9
Q

What is an example of a principle pathogen?

A

Streptococcus pneumonia

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10
Q

What is an opportunistic pathogen?

A

A pathogen that rarely causes disease

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11
Q

What is an example of an opportunistic pathogen?

A

Pseudomonas aeruginosis

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12
Q

Why is there a lower pathogen exposure in developed countries?

A
  • clean water
  • improved sanitisation
  • low density population
  • proper food handling
  • vaccination
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13
Q

Why is there higher pathogenic exposure in developing countries

A
  • poor water
  • low sanitation
  • high density of living
  • improper handling of food
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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)
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15
Q

How can Microorganisms enter the body?

A
  • Mouth
  • Urinogenital Tract
  • Conjunctive
  • Scratch, Injury
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16
Q

Once entered, where do microorganisms shed out>

A
  • mouth
  • conjunctive
  • urinogenital tract
  • anus
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17
Q

What does a pathogen need to be able to do when leaving to be successful?

A
  • transmit to a new host
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18
Q

What are the routes of transmission?

A
  • direct contact
  • Indirect contact
  • Droplet transmission
  • Hands
  • Vector-borne
  • Nosocomial
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19
Q

What are the 3 types of innate immune system defences?

A
  • Anatomical barriers
  • Humoral barriers
  • Cellular barriers
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20
Q

Give and examples of an anatomical barrier

A
  • skin
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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
Q

What are host defences in the urinary tract?

A
  • Mechanical processes (sphincter muscles prevent entry into bladder, urination flushes out bacteria)
26
Q

What are the defence mechanisms of the GI tract?

A
  • 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
Q

What is the role of normal flora of the GUT in host defence

A
  • 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
Q

What happens when pathogens break through host physical and chemical defence mechanisms?

A

They encounter the body’s immune defences

29
Q

What are the 2 types of immune responses?

A

Innate and specific (adaptive) immune responses

30
Q

Which response is antigen independent and which is antigen dependent?

A 
Innate = independent
Adaptive = dependent
31
Q

Which immune system results in immunological memory?

A

Specific immune responses

32
Q

How are microbial cells recognised by the innate immune system?

A
  • Microbial cells has Pathogen-associated molecular patterns (PAMPs) which are recognised by pattern recognition receptors (PRRs)
33
Q

What are examples of PRRs?

A
  • Toll-like receptors (TLRs)
  • Nod-like receptors (NLRs)
  • Rig-like receptors (RLR’s)
34
Q

After recognition, what do TLR’s do?

A
  • activate macrophage and dendritic cells
  • secrete pro-inflammatory mediators
  • initiate adaptive immune response
35
Q

Once inside the host, how do bacteria overcome a host’s defence mechanism?

A
  • They possess a bacterial armament
36
Q

What is the general process of bacteria virulence which leads to disease

A
  • Exposure
  • adherence
  • invasion
  • colonisation and growth
  • Toxicity or invasiveness
  • tissue damage, disease
37
Q

During early infection, how do bacteria interact and bind to a host cell surface

A
  • 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
Q

Give examples of afimbral adhesion

A
  • 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
Q

True of False: bacteria pathogens have specific tissue specificity when binding

A

True

40
Q

In microorganisms, what is motility and how does it work?

A
  • When bacteria can move to mucosal surfaces via a flagella
41
Q

In microorganisms, what is chemotaxis?

A
  • Bacteria can move to mucosal surface as a result of chemotactic responses
42
Q

What is the main essential growth requirement required to survive for bacteria?

A
  • Iron
43
Q

How do bacteria acquire iron?

A
  • Siderophore production
44
Q

How does siderophore production work?

A
  • 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
Q

Explain bacterial survival in regards to invasion and intracellular residence

A
  • 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
Q

What is the purpose of bacterial capsules in regards to evasion of host defences?

A
  • Prevents bacterial phagocytosis
47
Q

What is secretory IgA protease?

A
  • 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
Q

What is bacterial strategy for survival against sIgA

A
  • Production of SiGA proteases which destroys sIgA
49
Q

What are virulence factors that damage the host?

A
  • Endotoxin (embedded in gram negative outer membrane and creates an inflammatory response)
  • Exotoxins (excrete out of cell)
50
Q

What are 2 types of bacteria with extracellular virulence factors?

A
  • Streptococcus pyogenes

- Staphylococcus aureus

51
Q

True of false: The pathology induced in a host must relate to either the host response or the pathogen but not both

A

False: can be either or both

52
Q

What are 3 infectious disease outcomes?

A
  • Short term infection and recovery
  • Chronic infection
  • Death

BABS3081 (18 decks)

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