Session 1 - Introduction Flashcards
What is an infection?
Invasion of a host’s tissues by microorganisms. Damage caused by MO multiplication, toxins, or host response
What are the methods of acquiring infections?
- Contact – direct, indirect or vectors
- Inhalation – droplets or aerosols (droplets drop and aerosols stay suspended in the air, e.g. chickenpox).
- Ingestion – faecal to oral transmission
Modes of vertical transmission are mother to child before or at birth.
What are the 5 stages involved in a MO causing a disease?
1) Exposure
2) Adherence – MOs need to stick to surface
3) Invasion
4) Multiplication
5) Dissemination
What are the 5 factors which influence disease severity?
- Virulence factors
- Inoculum size – dose of MO taken by patient, varies by MO
- Antimicrobial resistance
- Site of infection
- Co-morbidities of patient, e.g. age, cancer, diabetes etc
What 3 steps are taken to asses if an infection is present?
History, examination and investigations
What are the two types of investigations you can perform? Give 2 examples of each
- Specific tests – Microscopy of bacterial cells, antigen detection,
- Supportive – General investigations, e.g. full blood count, C reactive protein (CRP) (test of acute phase proteins, stimulated by inflammation. Most infection causes inflammation)
How does antigen detection work?
Antigen detection – antibody at bottom of test tube, antibody aimed at antigen for a specific MO. If any of a specific antigen is present in the patient blood it sticks to the antibody. Another Ab then added which is attached to an enzyme. Substrate is added and if a product is produced, then antigen is present and therefore the patient is positive for a certain virus or bacteria.
Label the following
What is the difference in structure between gram positive and gram negative bacteria?
Gram negative have an outer membrane of lipopolysaccharides and proteins enveloping the peptidoglycan layer.
With regards to oxygen tolerance, what are the 4 types of bacteria?
1) aerobes
2) obligate aerobes
3) anaerobes
4) obligate anaerobes
