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ME2019 PART 2 > Pathogens and the Host > Flashcards

Pathogens and the Host Flashcards

1
Q

What is clinical infection characterised by?

A

Inflammation

Pain

Pyrexia (raised body temperature)

Tachycardia (increased heartrate)

Rigors (sudden feeling of cold with shivers)

Increased white cell count

Increased C reactive protein (CRP)

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2
Q

What is pyrexia?

A

Raised body temperature

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3
Q

What is tachycardia?

A

Increased heartrate

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4
Q

What are rigors?

A

Sudden feeling of cold with shivers

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5
Q

What is a pathogen?

A

An organism that can cause disease

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6
Q

What is a commensal?

A

An organism which is part of normal flora

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7
Q

What are examples of commensals?

A

E coli in the gut

Staph aureus in the nose

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8
Q

What is a skin commensal?

A

Coagulase-negative staphyloccii

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9
Q

When can coagulase-negative staphyloccii be pathogenic?

A

In the presence of foreign bodies (such as prosthetic heart valves)

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10
Q

What is Koch’s postulates?

A

The criteria used to identify the agent of a particular disease

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11
Q

What are the principles of Koch’s postulates?

A

Organism must be found in all cases of the disease

Able to be cultured outside the body for several generations

Should reproduce the disease on inoculation (vaccination)

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12
Q

What do non-sterile sites contain that sterile sites do not?

A

Commensals

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13
Q

What do we need knowledge of to determine if something is a pathogen?

A

Normal flora for the site

Organisms pathogenicity

Clinical context

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14
Q

What is pathogenicity?

A

Ability of an organism to cause disease

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15
Q

What is flora?

A

Collective bacteria and other microorganisms in an ecosystem

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16
Q

What does an organism need to be to cause an infection?

A

Infectivity (ability to become established)

Virulence (ability to cause harmful effects once established)

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17
Q

What is infectivity?

A

Ability to become established

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18
Q

What is virulence?

A

Ability to cause harmful effects once established

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19
Q

What are things that help infectivity?

A

Attachment (such as P-fimbriae on E coli)

Acid resistance (such as urease on helicobacter pylori)

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20
Q

What is an example of attachment helping infectivity?

A

P-fimbriae on E coli

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21
Q

What is an example of acid resistance helping infectivity?

A

Urease on helicobacter pylori

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22
Q

What is urease?

A

An enzyme that catalysis urea to ammonia and carbon dioxide

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23
Q

What is virulence supported by?

A

Invasiveness

Toxin production

Evasion of immune system

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24
Q

What is virulence specific to?

A

Strains, not species

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25
Q

What is an example of invasiveness?

A

Streptococcus pyogenes causing:

Necrotising fascilitis (flesh eating disease)

Cellulitis

Connective tissue breakdown

Fibrinolysis

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26
Q

What is haemolysis?

A

The rupture or destruction of red blood cells

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27
Q

What are the 3 types of haemolysis?

A

Alpha haemolytic (partial haemolysis, turns blood agar green)

Beta haemolytic (complete haemolysis, turns blood agar clear)

Non haemolytic

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28
Q

What is alpha haemolytic?

A

Partial haemolysis

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29
Q

What colour does alpha haemolytic turn blood agar?

A

Green

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30
Q

What is beta haemolytic?

A

Complete haemolysis

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31
Q

What colour does beta haemolytic turn blood agar?

A

Clear

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32
Q

What may different species of strepococci be?

A

Alpha, beta or non haemolytic

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33
Q

What is an example of an alpha haemolytic streptococci and what does it cause?

A

Streptococcus pneumoniae which causes:

Pneumonia

Meningitis

Septicaemia

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34
Q

What are beta haemolytic bacteria further identified by?

A

Lancefield groupings

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35
Q

What are lancefield groupings based on?

A

Surface antigens

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36
Q

What groups are in lancefield groupins?

A

A to G

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37
Q

What are the clinically most important lancefield groups?

A

A, B and D

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38
Q

What is a major group A beta haemolytic streptococci and what does it cause?

A

Streptococcus pyogenes which causes:

Sore throats

Cellulitis

Necrotising fascilitis

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39
Q

What is a toxin?

A

A poison that acts as an antigen in the body

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40
Q

What are the 3 kinds of toxins?

A

Exotoxins (released extracellularly)

Enterotoxins (exotoxins which act on the GI tract)

Endotoxins (structurally part of the gram negative cell wall)

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41
Q

What are exotoxins?

A

Toxins that are released extracellularly

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42
Q

What are enterotoxins?

A

Exotoxins that act on the GI tract

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43
Q

What are endotoxins?

A

Toxins that are structurally part of the gram negative cell wall

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44
Q

What does clostridium tetani produce?

A

Toxins that cause tetanus

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45
Q

What is tetanus?

A

Uncontrolled muscle spasm due to loss of inhibition at the neuromuscular junction

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46
Q

What is used for the immunisation of tetanus?

A

Antigenically modified toxin

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47
Q

What is a toxoid?

A

A chemically modified toxin that is no longer toxic but is still antigenic and can be used as a vaccine

48
Q

What are examples of bacteria that produce toxins?

A

Clostridium tetani

Clostridium perfringes

Clostridium difficile

49
Q

What does vibrio cholerae cause?

A

Uses enterotoxins to colonise in the small intestine and cause:

Increases cAMP levels (inhibits uptake of Na and Cl ions, and secretion of Cl and HCO3 ions)

Passive outflow of water

Cause of death by dehydration

50
Q

What are superantigens?

A

Class of antigen that cause non-specific activation of T cells resulting in massive cytokine release causing toxic shock

51
Q

What are superantigens produced by?

A

Certain exotoxins of strep pyogenes and staph aureus

52
Q

What do endotoxins cause?

A

Severe uncontrolled host response such as:

Cytokine production

Fever

Rigors

Hypotension

Collapse

53
Q

What are examples of gram negative cocci?

A

Neisseria spp

Moraxella catarrhalis

E coli

54
Q

What is the name of E coli?

A

Escherichia coli

55
Q

What kinds of reserves does E coli have?

A

Human and animal reservoirs

56
Q

What virulence machanisms does E coli have?

A

Pili

Capsule

Endotoxins

Exotoxins

57
Q

What does E coli do?

A

Ferments lactose

58
Q

What is a serotype?

A

Serologically distinguishable strain

59
Q

How many serotypes of E coli are there?

A

Over 160

60
Q

What are different kinds of virus pathogenic mechanisms?

A

Cell destruction following virus infection

Virus induced changes to cellular gene expression

Immunopathogenic disease

61
Q

What are different kinds of virus infections?

A

Acute infections

Latent infections

Chronic infections

Tumour virus infections

62
Q

What is an example of virus pathogenisis?

A

The transmission of influenza A:

1) Virus infects cells of the respiratory tract
2) Destruction of respiratory epithelium
3) Secondary bacterial infection
4) Altered cytokine expression leading to fever

63
Q

Viru

A
64
Q

What can the generation of novel influenza be caused by?

A

Antigenic drift (minor changes, natural mutations in the genes of flu viruses over time)

Antigenic shift (abrupt major changes in virus antigenic structure)

65
Q

What is antigenic drift?

A

Minor changes, natural mutations, in the genes of flu viruses over time

66
Q

What is antigenic shift?

A

Abrupt major changes in the virus antigenic structure

67
Q

What are enteroviruses?

A

Single stranded sense RNA viruses

68
Q

What are examples of enteroviruses?

A

Poliovirus

Coxsackie B viruses

69
Q

What are some conditions caused by enteroviruses?

A

Poliomyelitis (caused by poliovirus)

Aseptic meningitis

Myocarditis (caused bu coxsackie B virus)

Pancreatitis (caused by coxsackie B virus)

Respiratory infections

70
Q

What is viraemia?

A

The presence of viruses in the blood

71
Q

What can viruses do from the blood?

A

Infect neuronal tissues which will cause paralysis

72
Q

What is paralysis?

A

Loss of muscle function in part of your body

73
Q

What is a latent virus infection?

A

Virus that lies dormant in a cell and can start expressing genes in the future (reactivation)

74
Q

What is an example of a latent virus infection?

A

Herpes simplex virus

75
Q

What are the 2 types of herpes simplex virus?

A

Cold sores (type 1)

Genetial lesions (type 2)

76
Q

What is the pathogenisis of herpes virus infections?

A

1) Primary infection on epithelial cells
2) Virus migration to the ganglia
3) Virus reamins latent in nucleus (no virus replication)
4) Stimuli causes reactivation of the virus
5) Virus migration to epithelial cells leading to virus replication

77
Q

What are examples of viruses that can induce tumours?

A

Papilomaviruses (cervical carinoma)

Reteroviruses (lymphomas and leukaemias)

78
Q

What is the pathogenisis of human T-lymphotropic virus-1?

A

1) Transmission by blood and mother to child
2) Infects T cells
3) Modifies host cell gene expression using transactivating proteins (ones that cause transactivation, increased rate of gene expression)
4) Causes a variety of disease such as leukaemia
5) Directly responsible for the tumour

79
Q

What are the 2 kinds of host defence mechanisms?

A

Innate immunity

Acquired immunity

80
Q

What is innate immunity?

A

The non-specific first line of defence

81
Q

What is responsible for innate immunity?

A

Physical barriers such as the skin, gastric acid and mucus

Phagocytic cells that ingest foreign bodies (such as polymorphs and macrophages)

82
Q

What are different kinds of polymorphs?

A

Neutrophils

Eosinophils

Basophils

83
Q

What is opsonisation?

A

Immune process where particles are targeted for destruction by a phagocyte

84
Q

What is the process of optimisation?

A

1) Organism coated with antibody or compliment
2) Phagocyte has receptors for both and targets them
3) Efficiency of phagocytosis has improved

85
Q

What is acquired immunity?

A

A specific immune response to the antigen concerned and an immunological memory is created

86
Q

What is acquired immunity composed of?

A

Humoral (antibodies)

Cellular (T cells)

87
Q

What does humoral mean?

A

Relating to body fluids

88
Q

What is each organism a mix of? And what is this a mix of?

A

Each organism is a mix of antigens, and each antigen is a mix of epitopes

89
Q

What is an epitope?

A

Part of an antigen which an antbody attaches itself

90
Q

What is an antibody?

A

Y shaped protein used to neutralise pathogens, also known as immunoglobin

91
Q

What is an antibody also known as?

A

Immunoglobulin

92
Q

What are different kinds of antibodies?

A

Immunoglobulin M (primary response)

Immunoglobulin G (secondary response)

Immunoglobulin A (mucosal immunity)

Immunoglobulin E (allergy and helminth infections)

93
Q

What do B cells do when they recognise a specific epitope?

A

Differentiate into a plasma cell

94
Q

What is the differentiation of B cells into plasma cells initiated by?

A

Helper T cell

95
Q

What is a monoclonal antibody?

A

Specificity for a single epitope

96
Q

What is a polyclonal antibody?

A

Multiple specificity

97
Q

What is a plasma cell?

A

Fully differentiated B lymphocyte which produces a single type of antibody

98
Q

What does the compliment system form?

A

A cascade of 20 proteins

99
Q

What is the compliment system triggered by?

A

The combination of an antigen and its antigen trigger

100
Q

What are some functions of antibodies in infection?

A

Neutralising bacterial toxins

Neutralising viruses

Prevents adherance of microorganisms

Opsonises capsulated organisms

Useful means of diagnosis (serology)

101
Q

What does opsonises mean?

A

Makes more susceptible to the action of phagocytes

102
Q

What are functions of compliment proteins in infection?

A

Opsonisation

Lysis of gram negative organisms

Attracts polymorphs

103
Q

What is lysis?

A

Degradation of a cell by rupture of th cell wall or membrane

104
Q

Where does the humoral response happen?

A

Extracellularly

105
Q

When is humoral immunity mostly used?

A

In bacterial infection, causing acute inflammation

106
Q

What does humoral immunity cause?

A

Acute inflammation

107
Q

What is cell mediated immunity?

A

Immune response that does not involve antibodies but the activation of phagocytes and cytotoxic T cells and the release of various cytokines

108
Q

What is the process of cell mediated immunity?

A

1) Macrophages present antigen and stimulate T cells
2) Cytokines are produced and control the response
3) Th1 cells activate macrophages to ingest and kill pathogens
4) Cytotoxic T cells kill infected host cells or foreign cells

109
Q

What are the 2 kinds of active immunisation?

A

Natural (exposure/infection)

Artificial (vaccination)

110
Q

What are different kinds of vaccines?

A

Live attenuated

Killed, inactivated

Toxoid, modified toxin

111
Q

What are common vaccines for travellers?

A

Hepatitis A

Typhoid

Yellow fever

Rabies

112
Q
A
113
Q
A
114
Q
A
115
Q
A
116
Q
A

ME2019 PART 2 (45 decks)

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