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MCD > Microbiology 5 > Flashcards

Microbiology 5 Flashcards

1
Q

List the types of transmission of virus

A
  • Respiratory
  • Fecal oral
  • Contact
  • Zoonoses
  • Blood
  • Sexual contact
  • Maternal-neonatal
  • Germ line
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2
Q

What are fomites?

A

Snot.ect from a surface when an infected person touches them

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3
Q

What is intragenic transmission?

A

Where a health worker is the cause of infection.

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4
Q

What is a nosocomial infection?

A

An infection caught in the hospital.

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5
Q

What is vertical transmission?

A

From parent to offspring

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6
Q

What is horizontal transmission?

A

Any form of transmission not from parent to offspring.

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7
Q

What is germ line transmission?

A

Where the virus is part of the host genome.

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8
Q

What is viraemia?

A

Virus in the blood

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9
Q

What are the stages of dissemination from the site of entry?

A

Local infection to primary viraemia to amplification to secondary viraemia to the target organ.

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10
Q

What causes viral rashes?

A
  • Systemic viral transmission
  • Virus leaves the blood and enters the skin
  • Cells are destroyed by virus replication
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11
Q

Define the term tropism.

A

The predilection of viruses to infect certain tissues and not others.

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12
Q

How is tropism determined?

A
  • Can be defined by receptor interactions (susceptibility)
  • Ability to use the host cell to complete replication (permissivity)
  • Whether the virus can reach a tissue (accessibility).
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13
Q

How is the tropism of HIV determined?

A
  • Receptor use - CD4 and CCR5 or CXCR4 co receptors

- Delta 32 mutation in CCR5 leads to HIV resistance

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14
Q

What receptors does measles use?

A

Two receptors - CD155/SLAM and Nectin 4

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15
Q

Describe the pathway taken by the measles virus.

A
  • Virus enters new host - binds to SLAM on immune cells resulting in ummunosuppression
  • Virus exits from the infected host using nectin 4 on the airway epithelia
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16
Q

What determines tropism of HA (influenza) virus?

A
  • The virus enters through endosomes
  • Low endosomal pH triggers fusion
  • HA cleavage is required for exposure of fusion peptide (conformational change)
  • Depends on availability of host proteases
17
Q

Define the term pathogenicity

A

The ability of the virus to cause disease

18
Q

Define the term virulence

A

The capacity of a virus to cause disease

19
Q

What does viral disease depend upon?

A

Viral disease depends on how much replication the virus undergoes but is affected by other factors too such as the host response.

20
Q

What are the different patterns of virus infection?

A
  • Acute infection (followed by viral clearance)
  • Acute infection with accidental tissue damage
  • Persistence infection - latent& slow& transforming
  • Long incubations
  • Oncogenesis
21
Q

Define acute viral infection

A

Rapid onset of disease

22
Q

What are arboviruses?

A

Viruses spread by insects

23
Q

What is a systemic infection?

A

Infection through the whole body

24
Q

What is r0?

A

How many people will be infected by one infected person.

25
Q

What is a latent persistent infection?

A

An infection that is hiding in the cell waiting to cause an episode of reactivation.

26
Q

Give examples of acute infection

A
  • Colds and influenza.
  • Many unapparent or asymptomatic infections.
  • Smallpox (variola virus) and dengue haemorragic fever causes death
  • Poliovirus can cause poliomyelitis by accident& as can rubella
27
Q

Give examples of persistent viral infections

A
  • Chronic infection with low level replication of viruses in tissues which regenerate. Papillomaviruses in warts.
  • Chronic carriers of hepatitis B and C viruses.
28
Q

What are the strategies for viral persistence?

A
  • Evading immune surveillance by infecting tissues unlikely to be infected
  • MHC downregulation
  • Escape by mutation
29
Q

Give some examples of viruses that use strategies for viral persistence.

A
  • Measles
  • Herpes
  • Papillomavirus
30
Q

Give some examples of viruses that use latency.

A

Herpes simplex virus

31
Q

How does herpes simplex virus latency and reactivation occur?

A
  • Primary site of infection (epithelial cells)
  • Secondary site of infection and site of latent infection (sensory neuron)
  • Site of recurrent infection (epithelial cells)
32
Q

How can viruses cause cancer?

A
  • Viruses may encode oncogenes

- May interfere with the cell cycle to enhance their replication

33
Q

Give examples of viruses that cause cancers

A
  • Papillomaviruses encode inhibitors of tumour suppressor genes. This forces the cell into S phase.
  • Polyoma virus
  • HTLV-1 causes leukaemia
  • Hep B and C increase chance of hepatocellular carcinoma
  • Epstein Barr Virus causes lymphoma/carcinomas
34
Q

What affects the outcome of virus infection?

A
  • Virus sequence
  • Virus load
  • Host immune response/status
  • Host co-morbidity
  • Co infections
  • Other medications
  • Host genetics
  • Host age & gender
35
Q

Give an example of a virus whose sequence affects the outcome

A
  • Poliovirus
  • A single mutation in the genome can mean that one strain acts as a live attenuated vaccine
  • Another invades the motor neurone and causes flaccid paralysis (poliomyelitis).
36
Q

Give an example of a virus whose viral load affects the outcome

A

First child to be infected with chicken pox has a milder sibling than the second in the family.

37
Q

Give an example of coinfections

A
  • Secondary infection after influenza
  • HIV infected individuals more likely to get Kaposis Sarcoma
  • Hepatitis delta virus only affects people with hep B infection.
38
Q

Give some examples of predisposing co-mobidities and conditions for severe influenza.

A
  • Asthmatics and respiratory viruses
  • Obesity
  • Immunosuppression
  • Immunodeficiency
  • Elderly
  • Diabetes mellitus
  • Pregnancy

MCD (56 decks)

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