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Michaelmas Term 1 > The Anti-Social Microbe > Flashcards

The Anti-Social Microbe Flashcards

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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
Lysogenic phage aka
Temperate phage
26
Give an example of a lysogenic phage
E. Coli phage lambda
27
Describe the lysogenic phage life cycle
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
28
What is the most abundant biological entity on the planet?
- bacteriophage - 10^30 (more than stars) - 200Mt carbon in marine viruses
29
Many microbial infectious agents cannot
- survive in an environmental reservoir - they require direct host-to-host transmission - pathogen resides permanently in host population
30
When the infection is transitory, in what way do we regard the host?
Susceptible, or infected
31
Not all pathologies are
Beneficial to the pathogen - some arise from failed commensal relationships
32
How is continued transmission insured
One infection must give rise to at least one other infection R = 1
33
Describe Chlamydia trachomatis
- 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
34
What causes high rate of recombination among Chlamydia strains
Mixed infections
35
Define horizontal transmission
Passing of infectious agent among different individuals
36
Describe vertical transmission
Passing of infections from parent to offspring
37
List the routes by which vertical transmission can occur
- intracellular - transplacentally - via milk - during birth
38
Give an example of pathogen that is vertically transferred during birth
HIV
39
Describe maternal infections
- cause severe disease during pregnancy - not transmitted to offspring
40
Describe congenital infections
- mild or asymptomatic during pregnancy - can be vertically transmitted, resulting in congenital symptoms
41
Describe neonatal infections
Can lead to serious complications shortly after birth
42
Examples of maternal infections
- SARS Coronavirus - Hepatitis E virus - Ebola virus
43
Grace samples of maternal and neonatal infections
- influenza - Chlamydia trachomatis - Group B Streptococcus
44
Examples of neonatal infections
- Bordetella pertussis - Clostridium tetani - Respiratiry syncytial virus
45
List congenital and neonatal infections
- Herpes simplex virus - Treponema pallidum - Hepatitis B virus
46
Describe congenital infections
- Rubella virus - Parvovirus B19 - Toxoplasma gondii - Cytomegalovirus - Zika virus
47
List maternal and congenital infections
- Plasmodium spp. - Listeria monocytogenes
48
List infections that can be maternal, congenital or neonatal
- HIV - Varicella zoster virus
49
What happens when hosts become immune to further infection?
They are removed from the transmission system
50
Describe immunity
Has a duration of protection that can vary in length until host lifetime
51
Give an example of an infection whose immunity’s duration of infection is host lifetime
Measles
52
Describe measles
- 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
What is a ‘disease of childhood’
A single infection provides ‘life long immunity’
54
Give an example of an acute infection
Measles
55
Describe acute infections
- occur of a short period of time during which they pass on to another host - vulnerable to excess host death and immunity
56
How do pathogens decrease their vulnerability to excess host death and immunity
Establishing chronic infection
57
Describe chronic infection
- Pathogen remains in quiescent state in the host - can be reactivated to become infectious
58
Give examples of chronic infections
- chicken pox/shingles - tuberculosis
59
Describe chickenpox and shingles pathology
- 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
VZV
Varicella zoster virus
61
What are ‘dead end’ hosts?
Recipient species of pathogen infection are not capable of transmitting to another host
62
Give an example of dead end hosts
Rabies in humans ??
63
What happens if transmission among members of a new host species becomes established?
A novel infectious cycle emerges
64
Describe Rabies pathogenesis
- 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
What are the changes to behaviour that rabies induces called, and what are they?
Mad dog: - hydrophobia - aggression
66
What does SARS stand for?
Severe acute respiratory syndrome
67
What is SARS?
A zoonotic disease caused by the SARS coronaviruses
68
Describe the zoonotic transmission of SARS
Bats -> civets -> humans
69
Why are complex life cycles costly?
- survive in a variety of different environments - evade a variety of different immune responses
70
Schistosomiasis aka
Bilharzia
71
How is Schistosomiasis transmitted?
Humans are infected by contact with schistosome-contaminated water
72
Describe Schistosomiasis life cycle
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
What is the position of the snail in Schistosomiasis transmission?
Intermediate host
74
Describe the effect of HPV
Cervical cancer
75
HPV
Human papilloma viruses
76
Describe DFTD
Origin: Schwann cell Transmission: Biting
77
DFTD
Devil facial tumour disease
78
Describe CTVT
Affects: dogs, wolves, coyotes and jackals Origin: myeloid cell
79
CTVT
Canine transmissible venereal tumour
80
How is prion protein to pathogenic form achieved?
Autocatalysis
81
What produces prion proteins?
Normal host cells
82
Describe prion pathological conformations
- highly stable - can be transmitted orally - not inactivated by normal sterilisation techniques
83
What do prions cause?
TSEs
84
TSE
Transmissible spongiform encephalopathy
85
Give two examples of ways of studying disease burdens
- Disability affected life years (DALYs) - excess deaths
86
R0 =
Reproduction rate
87
The adaptive immune system is
Primed by previous exposure
88
Neurones are
Immunologically privileged, to prevent neuropathy
89
What is beneficial about the evolution of latency?
Allows the pathogen to survive in small populations
90
Most transmissions across to a second species result in a
Dead end
91
What is significant about bats?
They have enormous population size
92
We have changed our ecology by
Moving into the ecology of other organisms
93
Disease is fundamentally an
Ecological process
94
Give an example of a type of ‘lazy pathogen’
STIs
95
Prions aka
Alternative organism

Michaelmas Term 1 (42 decks)

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