9. Microbiology - Will Irving & Emma English Flashcards
State 3 things about virus size
Small
Filterable agents
20-250nm
Virus structure
- State 2 things about virus structure
- What does a virus contain?
- Simple / no organelles
2. Nucleic acid + proteins + sometimes lipid envelope
Virus metabolism
State 3 things about virus metabolism
Metabolically inert
Relies on host cell
Obligate Intracellular parasites
Virus replication
- How are component parts synthesised?
- Where will this happen?
- Control?
- What happens next?
- Independently
- May be in separate parts of cell
- Under separate control
- Subsequent assembly into new particles
Mature virus particle
- Also known as?
- What 2 things is it always made up of? Give the other names for these 2 things.
- What thing may or may not be present?
- Virion
- Nucleic acid = genome
Protein coat = capsid - Lipid envelope
Viral components: nucleic acid
- DNA: how stranded? Shape? Size?
- RNA: how stranded? Ss polarity? Shape? Size?
- DNA
Ds or ss / circular or linear / 3-200kb - RNA
ds or ss/ ss can be positive or negative polarity / linear or segmented / 5-10kb
Viral component: Proteins
- Capsid formation: discuss the shape
- Attachment: what determines viral tropism?
- Enzymes: what do they mainly do?
- Interference with cell function: give an example.
- Symmetrical
- There is a specific interaction between the viral ligand and the cellular receptor
- Macromolecular synthesis
- Stop apoptosis
Viral component: lipid envelope
- What is it derived from?
- What must it contain?
- What will stripping of envelope lead to?
- Enveloped viruses are generally more what?
- Host cell membranes
- External attachment proteins
- Loss of infectivity
- Fragile
Name the 6 steps of viral replication
- Attachment
- Entry
- Uncoating
- Macromolecular synthesis
- Assembly
- Release
Viral replication
1. Step 1 is attachment. What two things attach to each other?
2. Step 2 is entry. What 2 ways can a virus enter a cell?
Step 3 is coating
3. Step 4 is macromolecular synthesis. Multiple copies of which 2 things are made?
4. Macromolecular synthesis requires production of what type of RNA?
Step 5 is assembly
5. Step 6 is release. What process allows for release?
- Viral ligand to cellular receptor
- Endocytosis and fusion
- Viral genomes and viral proteins
- Positive ssRNA
- Budding
State the 4 effect of viruses on cells?
Acute cell death
Chronic infection
Latency
Transformation
Effect of viruses on cells - acute cell death
Give 2 ways the cell can die
Give an example
Cytolytic / cytocidal
Influenza virus on respiratory epithelial cells
Effect of viruses on cells - chronic infection
What happens in this case?
Give an example
Cell continually produces virus but survives
Hep B virus infection
Effect of viruses on cells - latency
- Replication?
- Is the viral genome present? Is viral protein made?
- Once infected…?
- Virus replication?
- Types of infection?
- Give an example
- No virus replication
- Viral genome present
No production of viral proteins - Once infected, always infected
- Virus replication can be reactivated
- Primary and secondary infections
- All herpes viruses eg. Herpes simplex
Effect of viruses on cells - transformation
What is meant by transformation?
Give an example
Immortalisation of the cell
Epstein Barr virus
Give 2 examples of viruses that cause cancer
Hep B - hepato cellular carcinoma
Epstein Barr virus - lymphomas
What are the 2 types of virus infections of the respiratory tract?
How serious are they?
URTI = upper respiratory tract infections
Common + relatively trivial
LRTI = lower respiratory tract infections
Potentially life-threatening
Name the infections in the following places:
- Nose
- Throat
- Sinuses
- Ear
- Epiglottis
- Larynx
- Rhinitis
- Pharyngitis
- Sinusitis
- Otitis media/ otitis externa
- Epiglottitis
- Laryngitis
URTI
- How common?
- Usual aetiology?
- What kind of secondary infections are common? (Name 2)
- Very common
- Viral
- Bacterial and fungal
Viral URTIs
- Name 3
- What may this predispose to? Give 2 examples
- Rhinoviruses/ parainfluenza viruses/ adenoviruses
- Secondary bacterial infection
Bronchitis/ pneumonia
Name 2 things that can cause pharyngitis/ tonsillitis and give an example for each
Viruses = adenoviruses Bacteria = strep pyogenes
Give an example of 4 viruses that cause LRTI
Influenza virus
Respiratory syncytial virus
Varicella zoster virus
Measles virus
Influenza viruses
- Shape / polarity / type of genome?
- How many segments? How many proteins do they encode?
- Name 2 viral proteins
- Name the types? What 2 things is this on the basis of?
- Name the subtype? What is this on the basis of?
- Segmented negative ssRNA
- 8 segments encode 11 proteins
- Haemagglutinin and neuraminidase
- A / B / C
Based on internal proteins and matrix - A only
Based on surface proteins (HA/NA)
What are the 2 major components to the influenza?
Respiratory tract symptoms
Systemic symptoms
Pathogenesis of influenza
- What is meant by pneumotropic virus?
- The infection strips of the respiratory epithelium- so the infection is what?
- Which 2 innate defence mechanisms does it remove?
- The virus doesn’t circulate in the blood but what is produced that does circulate in the blood?
- Infects cells lining the respiratory tract down to the alveoli
- Lytic
- Mucous secreting cells and cilia
- Interferons
Complications of influenza
- In the respiratory tract 2 types of pneumonia can occur. What are the 2 types and what kind of cell infiltrate is in each?
- What cardiovascular complication can occur?
- What CNS complication can occur?
- Primary viral pneumonia = mononuclear cell infiltrate
Secondary bacterial pneumonia = PMNL infiltrate - Myocarditis
- Encephalitis
Influenza: high risk patients
- Patients with pre-existing diseases. Name 3.
- Age?
- Other 2 categories?
- Lung disease / cardiac disease / renal disease
- Over 65 years old
- Pregnant women
Children
Influenza epidemiology
- Name 3 types of epidemics that cause influenza
- What 2 things cause these epidemics?
- Annual seasonal epidemics
Unpredictable worldwide epidemics
Pandemics and inter-pandemic epidemics - Antigenic drift and antigenic shift
Antigenic drift
- Which 2 influenza virus types does it occur in?
- Define antigenic drift including the percentage of amino acid sequence change
- What is this type of mutation responsible for?
- Influenza A and B viruses
- Random spontaneous mutations in viral genes encoding HA and NA
1-2% amino acid sequence change - Interpandemic epidemics
Antigenic shift
- Which influenza virus type does it occur in?
- Define antigenic shift, including percentage amino acid sequence change
- What is antigenic shift responsible for?
- Name 3 influenza A reservoirs.
- What is a mixing vessel for both human and avian viruses?
- Influenza A viruses only
- Genetic reassortment between human and non-human viruses leading to a new subtype
More then 20% amino acid difference - Emergence of new pandemic strains
- Wild aquatic shore birds / humans / other animals
- Pigs
Key measures to combat pandemic flu
- Medical treatment is one, what are the other 2?
- Explain 4 aspects of medical treatment
- Infection control and vaccination
2. Oxygen therapy / anti-viral drugs / antibiotics / ITU support
Respiratory syncytial virus
- What type of enveloped virus is it?
- Polarity and type of genome?
- How many polypeptides does it encode?
- Pattern of infection? Season?
- Popularity?
- Enveloped paramyxovirus
- Negative ssRNA
- 9 polypeptides
- Highly seasonal infection (winter)
- Extremely common
RSV (respiratory syncytial virus)
- What does it cause in infants? Give an example of 2
- Hospitalisation rates?
- Mortality? 3 exceptions?
- What 2 things does it require?
- Re-infection? How?
- LRTI
bronchiolitis / pneumonia - High hospitalisation rates
- Low mortality
Unless congenital heart disease / congenital lung disease / immunodeficiency - Rapid diagnosis and appropriate infection control measures
- Re-infection occurs throughout life - antigenic drift