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MD2001 Week 5 > Introduction to Microbial Infection > Flashcards

Introduction to Microbial Infection Flashcards

1
Q

What are Koch’s postulates?

A

Bacteria must be present in every case of the disease

The bacteria must be isolated from the host with the disease and grown in pure culture

The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host

The bacteria must be recoverable from the experimentally infected host

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2
Q

What does the innate immune system contain?

A

Normal microbiota

Physical barriers

Chemical barriers

Phagocytic cells

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3
Q

How does normal microbiota defend?

A

Competes with pathogens for colonisation sites

Produce antibiotic substances supressing growth of competing organisms

May produce toxic metabolic products to inhibit other micro-organisms

Alter pH

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4
Q

What is normal microbiota suppressed by?

A

Antibiotics

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5
Q

What do lactobacilli do?

A

Conversion of carbohydrates to acidic products

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6
Q

Where is lactobacilli found?

A

Vagina

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7
Q

What are some physical barriers?

A

Skin

Mucomuciliary clearance

Flushing

Peristalsis

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8
Q

How does the skin act as a physical barrier?

A

Secretes sebum and fatty acids to inhibit growth

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9
Q

What is mucomuciliary clearance?

A

Particles settle on sticky mucus of respiratory epithelium

Debris transported by cilia to oropharynx where it is swallowed

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10
Q

What are some chemical barriers?

A

Mucus

Antimicrobial proteins

Gastric acid

Plasma proteins

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11
Q

Example of anitmicrbial proteins

A

Lysozyme

Lactoferrin

Defensins

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12
Q

Example of plasma proteins

A

Complement

C-reactive proteins

Mannose-binding lectin

Transferrin

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13
Q

What is the function of lysozyme?

A

Catalyses the destruction of the cell walls of certain bacteria

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14
Q

What is the function of lactoferrin?

A

Restricts iron availability to bacteria

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15
Q

Example of phagocytic cells

A

Macrophages

Neutrophils

Monocytes

Dendritic cells

Mast cells

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16
Q

What are the ways an infection process can begin?

A

Invading host tissues

Exerting effects from mucosal surfaces

17
Q

What is the definition of commensal?

A

A micro-organism which forms part of the normal host microbiota

18
Q

What is a pathogen?

A

A micro-organism capable of causing an infection

19
Q

What is pathogenicity?

A

The capacity to cause disease

20
Q

What is virulence?

A

Measure of the capacity to cause disease

21
Q

What is an obligate pathogen?

A

Almost always associated with disease

HIV

22
Q

What is a conditional pathogen/

A

May cause disease if certain conditions are met

e.g Bacteroides fragilis

Staphylococcus aureus

23
Q

What is an opportunistic pathogen?

A

Usually only infections immunocompromised patients

e.g Pneumocystis jiroveci

24
Q

What are the 6 steps of infection?

A

Recognition

Attachment and entry

Multiplication

Evasion of host defences

Shedding

Damage

25
Q

How can infections be established in healthy hosts?

A

Microbes with specific mechanisms for attachment and penetration of host’s body surfaces

Microbes introduced into host by biting arthropods

Microbes introduced into host via skin wounds or animal bites

Microbes able to infect only when host defences are impaired

26
Q

What is tissue tropism?

A

The affinity of a pathogen to a specific tissue

27
Q

What can affect tissue tropism?

A

Cell receptors

Transcription factors

Local temperature

Physical

Barriers

pH

28
Q

What tissues does influenza have a high tropism for?

A

Cilia and microvilli on tracheal epithelium

29
Q

What tissues does vibrio cholerae have a high tropism for?

A

Intestinal epithelium

30
Q

What tissues does helicobacter pylori have a high tropism for?

A

Gastric mucosa

31
Q

What are virulence factors?

A

The factors which allow a bacteria to cause a disease

32
Q

What are the virulence factors?

A

Toxin secretion

Antibiotic resistance

Pilus formation

Capsule

Ion transport systems

Adhesion factors

Enzymes- proteases, DNAses, lipases

33
Q

What are the two bacterial toxins?

A

Endotoxins

Exotoxins

34
Q

Describe endotoxins

A

Low toxicity

Part of the cell wall of gram negative bacteria

Lipopolysaccharide

Low specificity

35
Q

Describe exotoxins?

A

Highly toxic

Secreted from bacterial cells

Produced by both gram positive and gram negative bacteria

Can be converted into toxoids for vaccine use

36
Q

Example of exotoxins

A

Tetanus toxin

Cholera toxin

Botulinum toxin

37
Q

What are some important examples of antibiotics?

A

Meticillin-resistant Staphylococcus aureus (MRSA)

Vancomycin-resistant Staphylococcus aureus (VRSA)

HIV

Malaria

38
Q

What is transmission dependent on?

A

Number of micro-organisms shed

Number of micro-organisms required to infect a fresh host

Micro-organism’s stability in the environment

MD2001 Week 5 (10 decks)

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