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Michaelmas Term 1 > The Anti-Social Microbe > Flashcards

The Anti-Social Microbe Flashcards

1
Q

Describe viruses as a pathological infectious agent

A
  • ssRNA, dsRNA, ssDNA, dsDNA
  • can integrate into host genome
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2
Q

Describe bacteria as a pathological infectious agent

A

wide variety

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3
Q

Describe protists as a pathological infectious agent

A

Wide variety

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4
Q

Describe multi-called eukarya as a pathological infectious agent

A

Helminths are visible to the human eye, but behave like microbes

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5
Q

Describe host-derived pathological infectious agents

A
  • infectious cancers (host cancer cells that have become infectious)
  • prions
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6
Q

Give examples of viruses

A
  1. Phage lambda
  2. Influenza
  3. SARS-CoV-2
  4. Ebola
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7
Q

Give examples of bacterial pathogens

A
  1. Mycobacterium tuberculosis
  2. Yersinia pestis
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8
Q

Give examples of protist pathogens

A
  • Trypanosoma brucei gambiense
  • Plasmodium falciparum
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9
Q

Give examples of multi-celled Eukarya pathogens

A
  • Schistosoma mansoni
  • Trichuris trichiura
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10
Q

Give examples of host-derived infectious cancers

A
  • Devil facial tumour disease
  • canine transmissible venereal tumour
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11
Q

Give examples of prions

A
  • Kuru (humans)
  • CJD and vCJD (humans)
  • Scrapie (sheep)
  • BSE (cattle)
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12
Q

What are prions?

A

Misfolded host-derived proteins

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13
Q

Infection is not necessary

A

A pathological process (it is also required by commensals and mutualistic symbionts)

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14
Q

What is pathology caused by?

A

Pathogen transmission from infection source to host

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15
Q

Describe the actions of a lytic bacteriophage as an infectious agent

A
  1. Environmental phage absorbs to bacterial host
  2. Phage injects DNA and it circularises- remains separate from host DNA
  3. Replicate DNA at host’s expense
  4. Genes are transcribed and translated by host machinery to produce phage proteins
  5. Virions assembled
  6. Virions released into environment by bacterial lysis
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16
Q

Give an example of a type of bacteriophage

A

Lytic bacteriophage

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17
Q

What is a virion?

A

Phage particle

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18
Q

What does bacterial lysis cause?

A

Cell death

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19
Q

What is it called when virions are released into the environment by bacterial lysis

A

A pathology

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20
Q

When is the phage life cycle complete?

A

When another bacterium is infected

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21
Q

Describe a lytic phage

A

Bacterial cells are lysed and the phage progeny infect new hosts

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22
Q

Give an example of a lytic phage

A

Bacteriophage T4 that infects E. Coli

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23
Q

What is a lysogenic phage?

A
  • phage genome integrates into host DNA
  • some persist as episome
  • some lyse cell
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24
Q

Episome

A

Phage DNA inside a bacterial body that can replicate independently of the host, and also in association with a chromosome with which it becomes integrated

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25
Q

Lysogenic phage aka

A

Temperate phage

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26
Q

Give an example of a lysogenic phage

A

E. Coli phage lambda

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27
Q

Describe the lysogenic phage life cycle

A
  1. Phage infects cell
  2. Phage DNA integrates into host genome
  3. Cell divides - prophage DNA passed on to daughter cells
  4. Under stress, phage DNA excised from bacterial chromosome, and enters lytic cycle
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28
Q

What is the most abundant biological entity on the planet?

A
  • bacteriophage
  • 10^30 (more than stars)
  • 200Mt carbon in marine viruses
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29
Q

Many microbial infectious agents cannot

A
  • survive in an environmental reservoir
  • they require direct host-to-host transmission
  • pathogen resides permanently in host population
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30
Q

When the infection is transitory, in what way do we regard the host?

A

Susceptible, or infected

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31
Q

Not all pathologies are

A

Beneficial to the pathogen - some arise from failed commensal relationships

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32
Q

How is continued transmission insured

A

One infection must give rise to at least one other infection
R = 1

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33
Q

Describe Chlamydia trachomatis

A
  • an obligate intracellular pathogen of humans
  • relatively small genome (1Mbp, ~1000 genes)
  • evidence for genome reduction
  • isolates of very low diversity
  • high rates of recombination among strains
  • not subject to genome decay
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34
Q

What causes high rate of recombination among Chlamydia strains

A

Mixed infections

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35
Q

Define horizontal transmission

A

Passing of infectious agent among different individuals

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36
Q

Describe vertical transmission

A

Passing of infections from parent to offspring

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37
Q

List the routes by which vertical transmission can occur

A
  • intracellular
  • transplacentally
  • via milk
  • during birth
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38
Q

Give an example of pathogen that is vertically transferred during birth

A

HIV

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39
Q

Describe maternal infections

A
  • cause severe disease during pregnancy
  • not transmitted to offspring
40
Q

Describe congenital infections

A
  • mild or asymptomatic during pregnancy
  • can be vertically transmitted, resulting in congenital symptoms
41
Q

Describe neonatal infections

A

Can lead to serious complications shortly after birth

42
Q

Examples of maternal infections

A
  • SARS Coronavirus
  • Hepatitis E virus
  • Ebola virus
43
Q

Grace samples of maternal and neonatal infections

A
  • influenza
  • Chlamydia trachomatis
  • Group B Streptococcus
44
Q

Examples of neonatal infections

A
  • Bordetella pertussis
  • Clostridium tetani
  • Respiratiry syncytial virus
45
Q

List congenital and neonatal infections

A
  • Herpes simplex virus
  • Treponema pallidum
  • Hepatitis B virus
46
Q

Describe congenital infections

A
  • Rubella virus
  • Parvovirus B19
  • Toxoplasma gondii
  • Cytomegalovirus
  • Zika virus
47
Q

List maternal and congenital infections

A
  • Plasmodium spp.
  • Listeria monocytogenes
48
Q

List infections that can be maternal, congenital or neonatal

A
  • HIV
  • Varicella zoster virus
49
Q

What happens when hosts become immune to further infection?

A

They are removed from the transmission system

50
Q

Describe immunity

A

Has a duration of protection that can vary in length until host lifetime

51
Q

Give an example of an infection whose immunity’s duration of infection is host lifetime

A

Measles

52
Q

Describe measles

A
  • highly infectious by respiratory route
  • humans = only known reservoir
  • related to animal viruses
  • ‘disease of childhood’
  • can only persist in host populations of sufficient size
53
Q

What is a ‘disease of childhood’

A

A single infection provides ‘life long immunity’

54
Q

Give an example of an acute infection

A

Measles

55
Q

Describe acute infections

A
  • occur of a short period of time during which they pass on to another host
  • vulnerable to excess host death and immunity
56
Q

How do pathogens decrease their vulnerability to excess host death and immunity

A

Establishing chronic infection

57
Q

Describe chronic infection

A
  • Pathogen remains in quiescent state in the host
  • can be reactivated to become infectious
58
Q

Give examples of chronic infections

A
  • chicken pox/shingles
  • tuberculosis
59
Q

Describe chickenpox and shingles pathology

A
  • VZV particles reach mucosal epithelial sites of entry
  • spreads via local replication to lyphoid tissues and T cells
  • latency established in sensory ganglia
  • reactivation results in replication in the skin, producing infectious lesions
60
Q

VZV

A

Varicella zoster virus

61
Q

What are ‘dead end’ hosts?

A

Recipient species of pathogen infection are not capable of transmitting to another host

62
Q

Give an example of dead end hosts

A

Rabies in humans ??

63
Q

What happens if transmission among members of a new host species becomes established?

A

A novel infectious cycle emerges

64
Q

Describe Rabies pathogenesis

A
  • spread between hosts by biting
  • virus moves through host nervous system intracellularly
  • promotes changes to behaviour in brain
  • virus growth in salivary glands promotes spread
65
Q

What are the changes to behaviour that rabies induces called, and what are they?

A

Mad dog:
- hydrophobia
- aggression

66
Q

What does SARS stand for?

A

Severe acute respiratory syndrome

67
Q

What is SARS?

A

A zoonotic disease caused by the SARS coronaviruses

68
Q

Describe the zoonotic transmission of SARS

A

Bats -> civets -> humans

69
Q

Why are complex life cycles costly?

A
  • survive in a variety of different environments
  • evade a variety of different immune responses
70
Q

Schistosomiasis aka

A

Bilharzia

71
Q

How is Schistosomiasis transmitted?

A

Humans are infected by contact with schistosome-contaminated water

72
Q

Describe Schistosomiasis life cycle

A
  1. Infective cercariae swim to the host and penetrate the skin
  2. Migrate through tissue and survive in the veins
  3. Eggs deposited
  4. Move to intenstine
  5. Released into environment
  6. Eggs hatch into miracida which infect snails
  7. Growth of sporocysts in snail results in cericariae release, completing cycle
73
Q

What is the position of the snail in Schistosomiasis transmission?

A

Intermediate host

74
Q

Describe the effect of HPV

A

Cervical cancer

75
Q

HPV

A

Human papilloma viruses

76
Q

Describe DFTD

A

Origin: Schwann cell
Transmission: Biting

77
Q

DFTD

A

Devil facial tumour disease

78
Q

Describe CTVT

A

Affects: dogs, wolves, coyotes and jackals
Origin: myeloid cell

79
Q

CTVT

A

Canine transmissible venereal tumour

80
Q

How is prion protein to pathogenic form achieved?

A

Autocatalysis

81
Q

What produces prion proteins?

A

Normal host cells

82
Q

Describe prion pathological conformations

A
  • highly stable
  • can be transmitted orally
  • not inactivated by normal sterilisation techniques
83
Q

What do prions cause?

A

TSEs

84
Q

TSE

A

Transmissible spongiform encephalopathy

85
Q

Give two examples of ways of studying disease burdens

A
  • Disability affected life years (DALYs)
  • excess deaths
86
Q

R0 =

A

Reproduction rate

87
Q

The adaptive immune system is

A

Primed by previous exposure

88
Q

Neurones are

A

Immunologically privileged, to prevent neuropathy

89
Q

What is beneficial about the evolution of latency?

A

Allows the pathogen to survive in small populations

90
Q

Most transmissions across to a second species result in a

A

Dead end

91
Q

What is significant about bats?

A

They have enormous population size

92
Q

We have changed our ecology by

A

Moving into the ecology of other organisms

93
Q

Disease is fundamentally an

A

Ecological process

94
Q

Give an example of a type of ‘lazy pathogen’

A

STIs

95
Q

Prions aka

A

Alternative organism

Michaelmas Term 1 (42 decks)

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