Session 1 ILOs - Introduction to infection and microbes Flashcards
Definition of infection
Infection is the invasion and multiplication of micro-organisms in a host’s tissues that are not normally present (may be symptomatic or asymptomatic)
Explain the 2 types of transmission: Horizontal (diff types) and vertical
Horizontal:
- Contact (direct, indirect or vectors)
- Inhalation (droplets or aerosols)
- Ingestion (faecal-oral)
Vertical
- From mother to child (before or during birth)
Explain how we know patients have an infection (including the meaning of the 2 types of investigations)
- History
- Symptoms
- Potential exposure - Examination
- Organ dysfunctions - Investigations
- Specific e.g. swabs etc. for bacteriology/virology - tries to identify the causative organism
- Supportive e.g. CRP, FBCs etc - tells you if the patient has an infection, but can’t give you a name
Name the 4 main categories of micro-organisms (smallest first)
- Viruses
- Bacteria
- Fungi
- Parasites
Name 3 key features of a model virus (from diagram)
- Protein coat
- Spikes (for attaching to specific cell surfaces)
- Nucleic acid (genetic code - DNA or RNA)
Name 3 key features of a model bacterium (from diagram)
- Ribosomes (smaller than human ribosomes)
- Plasmids (smaller circles of DNA - transferable DNA)
- Capsule and cell wall (polysaccharide molecules - immunogenic)
List the 3 bacterial shapes (2 main ones)
- Coccus (round)
- Bacillus (rod)
- Spirillus (very few with clinical importance!)
List the 2 ways coccus bacterial are arranged
- Clusters
- Chains
Outline the differences between gram positive and gram negative bacteria
Gram positive:
- Purple stain is retained = appears purple
- No outer membrane of lipopolysaccharide
- Primarily exudes exotoxins
- Thick outer peptidoglycan layer (multilayered)
Gram negative:
- Purple stain is NOT retained
- Lipopolysaccharide outer membrane
- Primarily exudes endotoxins
- Only thin peptidoglycan layer (single layered)
Name some virulence factors (promote bacteria) and outline the 2 types of toxins
Virulence factors:
- Host entry (e.g. polysaccharide capsule)
- Adherence to host cells (e.g. fimbriae)
- Invasiveness (e.g. enzymes)
- Iron sequestration (siderophores)
Toxins:
- Exotoxins
- Endotoxins
Name the 2 types of fungi - give 2 examples of each
Yeasts - single celled
e. g. Candida albicans (thrush)
e. g. Cryptococcus neoformans
Moulds - multicelled
e. g. Aspergillus species
e. g. Dermatophytes (ringworm/athletes foot)
Name the 2 types of parasites - give 2 examples of each
Protozoa - single celled
e. g. Giardia lamblia
e. g. Plasmodium falciparum
Helminths - multicelled or worms
e. g. Roundworms
e. g. Tapeworms