Concepts of microbiology Flashcards
What are the general properties of viruses
-small size
-have RNA or DNA
They are metabolically inert
-do not possess ribosomes/protein synthesis
-some have enzymes
What are some effects of viruses on cells
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
What is a capsomer
Protein unit that makes up the caspid (protein shell) of a virus
What is a clinical example of a virus which is transmitted through gastrointestinal tract
Rotavirus
How can a virus be spread via inoculation
Skin abrasions
Mucous membranes
Transfusions
Transplants
Injections
Bites
Name a virus which is transmitted through inoculation
Hepatitis B
What is congenital transmittion
Transmission from a mother to the foetus
Give examples of diseases which affect each of the following organs
Nervous system
Respiratory tract
Localised diseases of skin & mucous membranes
Eye
Liver
Salivary glands
Gastrointestinal tract
What type of specimen can be obtained to identify disease
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
What sample must be obtained for antigen detection
Blood sample
What is the name of the first class of antibody produced during infection
IgM
What does IgG represent
Change in antibody class (usually after about 2 weeks from initial infection)
What are the key stages of viral replication
Attachment
Penetration
Uncoating
Synthesis of viral components
Assembly
Release
Vaccines which stimulate the production of antibodies against viruses are still ineffective against which viruses
The viruses which cause the common cold and Aids
How are envelope proteins made
Ribosomes on the host cells endoplasmic reticulum
What are the key surface proteins of the influenza virus
Haemagglutinin
-Glycoprotein
-Sialic acid binding
-14 H types
Neuraminidase
-Glycoprotein
-Virion release
-9 N types
What processes of change are the surface proteins of influenza susceptible to
Antigenic drift
-Minor changes in surface structure -Point mutations
-Epidemics
-A,B & C drift
Antigenic shift
-Major change
-Recombination
-Pandemics
-Only influenza A
How can bird influenza infect humans
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
What is a Prions disease
Transmissible Spongiform Encephalopathies
-Fatal neurological diseases associated with the accumulation within the CNS of insoluble aggregates of a cell membrane protein called prion protein
Where is the name prion derived from
Proteinaceous Infectious Particle
What may explain how prion proteins can be incredible resistant to disinfectants
Contains neither DNA or RNA
What structure does an abnormal prion protein contain
Beta pleated sheets
-much more difficult for body to degrade
How can prion diseases occur
Infection
Genetic inheritance
Sporadic (1 per million)
What causes prion diseases
Accumulation of an abnormal form of a natural protein
Why is there no immune response to prions disease
The accumulation if of a natural protein in an abnormal form meaning the body does not detect a foreign body
What is unique to prion proteins as infectious agents
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
What causes variant CJD
Linked to consumption of contaminated food material of BSE
How can Iatrogenic CJD be transmitted
Surgical instruments
Contaminated hormones/grafts
Kuru (cannibalism)
What are the types of CJD
Sporadic (sCJD)
Familial (fCJD)
Iatrogenic (iCJD)
Variant (vCJD)
Why is variant CJD still a concern in healthcare
-Infectious agent can be difficult to clean from surgical instruments
-Residual infectivity can survive steam sterilization
-Incubation period - decades
-Asymptomatic/pre-symptomatic carriage
What precautions are necessary when providing dental treatment for CJD cases
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
What type of CJD is due to contaminated food
vCJD
