Concepts of microbiology

Question 1

What are the general properties of viruses

Answer 1

-small size
-have RNA or DNA

They are metabolically inert
-do not possess ribosomes/protein synthesis
-some have enzymes

Question 2

What are some effects of viruses on cells

Answer 2

Cell death: HSV I & effect on mucosal epithelial cells

Transformation(cancerous): Human papilloma virus & oral cancers

Latent infection (no obvious effect): HSV I and recurrent Herpes labialis

Question 3

What is a capsomer

Answer 3

Protein unit that makes up the caspid (protein shell) of a virus

Question 4

What is a clinical example of a virus which is transmitted through gastrointestinal tract

Answer 4

Rotavirus

Question 5

How can a virus be spread via inoculation

Answer 5

Skin abrasions
Mucous membranes
Transfusions
Transplants
Injections
Bites

Question 6

Name a virus which is transmitted through inoculation

Answer 6

Hepatitis B

Question 7

What is congenital transmittion

Answer 7

Transmission from a mother to the foetus

Question 8

Give examples of diseases which affect each of the following organs

Answer 8

Nervous system
Respiratory tract
Localised diseases of skin & mucous membranes
Eye
Liver
Salivary glands
Gastrointestinal tract

Question 9

What type of specimen can be obtained to identify disease

Answer 9

Swabs, faeces, aspirates, plasma, CSF, vesicle fluids, urine​
-Nucleic acid detection e.g, HSV detection​
(other methods available but used infrequently)​

Plasma​
-Monitoring by PCR e.g. HIV load ​

Serum​
-Serology e.g., Hepatitis B antibody titres​

Question 10

What sample must be obtained for antigen detection

Answer 10

Blood sample

Question 11

What is the name of the first class of antibody produced during infection

Answer 11

IgM

Question 12

What does IgG represent

Answer 12

Change in antibody class (usually after about 2 weeks from initial infection)

Question 13

What are the key stages of viral replication

Answer 13

Attachment
Penetration
Uncoating
Synthesis of viral components
Assembly
Release

Question 14

Vaccines which stimulate the production of antibodies against viruses are still ineffective against which viruses

Answer 14

The viruses which cause the common cold and Aids

Question 15

How are envelope proteins made

Answer 15

Ribosomes on the host cells endoplasmic reticulum

Question 16

What are the key surface proteins of the influenza virus

Answer 16

Haemagglutinin
-Glycoprotein
-Sialic acid binding
-14 H types

Neuraminidase
-Glycoprotein
-Virion release
-9 N types

Question 17

What processes of change are the surface proteins of influenza susceptible to

Answer 17

Antigenic drift
-Minor changes in surface structure -Point mutations
-Epidemics
-A,B & C drift

Antigenic shift
-Major change
-Recombination
-Pandemics
-Only influenza A

Question 18

How can bird influenza infect humans

Answer 18

Pigs
They contain receptors which both human and bird flu viruses are compatible with allowing human and bird flu genes to combine inside pig cells

Question 19

What is a Prions disease

Answer 19

Transmissible Spongiform Encephalopathies

-Fatal neurological diseases associated with the accumulation within the CNS of insoluble aggregates of a cell membrane protein called prion protein

Question 20

Where is the name prion derived from

Answer 20

Proteinaceous Infectious Particle

Question 21

What may explain how prion proteins can be incredible resistant to disinfectants

Answer 21

Contains neither DNA or RNA

Question 22

What structure does an abnormal prion protein contain

Answer 22

Beta pleated sheets
-much more difficult for body to degrade

Question 23

How can prion diseases occur

Answer 23

Infection
Genetic inheritance
Sporadic (1 per million)

Question 24

What causes prion diseases

Answer 24

Accumulation of an abnormal form of a natural protein

Question 25

Why is there no immune response to prions disease

Answer 25

The accumulation if of a natural protein in an abnormal form meaning the body does not detect a foreign body

Question 26

What is unique to prion proteins as infectious agents

Answer 26

A change in shape/structure of the protein can determine where the prion protein pathology occurs within the brain along with its susceptibility to inactivation agents such as chemical disinfectants and steam sterilization

Question 27

What causes variant CJD

Answer 27

Linked to consumption of contaminated food material of BSE

Question 28

How can Iatrogenic CJD be transmitted

Answer 28

Surgical instruments
Contaminated hormones/grafts
Kuru (cannibalism)

Question 29

What are the types of CJD

Answer 29

Sporadic (sCJD)
Familial (fCJD)
Iatrogenic (iCJD)
Variant (vCJD)

Question 30

Why is variant CJD still a concern in healthcare

Answer 30

-Infectious agent can be difficult to clean from surgical instruments
-Residual infectivity can survive steam sterilization
-Incubation period - decades
-Asymptomatic/pre-symptomatic carriage

Question 31

What precautions are necessary when providing dental treatment for CJD cases

Answer 31

Depending on the risk of the tissues involved the instruments should be: LOW
-Reprocess instruments according to best practice and return to use

MEDIUM/HIGH
-Dispose of instruments by incineration
-Quarantine instruments for re-use exclusively on the same patient

Question 32

What type of CJD is due to contaminated food

Answer 32

vCJD