Nature of Infection Flashcards
1
Q
Describe germ theory.
A
- Proposed criteria to prove microorganisms were responsible for cause of disease
- Proved by Koch and Pasteur
2
Q
What are Koch’s postulates?
A
- Microorganism found in abundance in all organisms suffering from the disease but not found in healthy organisms.
- Microorganism isolated from a diseased organism and grown in pure culture.
- Cultured microorganism should cause disease when introduced into a healthy organism.
- Microorganism re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
3
Q
Define vaccination.
A
- Administration of antigenic material (a vaccine) to stimulate an individual’s immune system to develop adaptive immunity to a pathogen
4
Q
How does the microbiome develop from birth?
A
- Until birth, foetus raised in sterile environment
- Exposed to pathogens from environment once born
- ‘Flora’ form on surfaces of skin, intestines and GU tract
- Microbiome - genetic material of all the microbes that live on and inside the human body.
5
Q
Describe the relationship between the human host and microbes in the microbiome. Explain why.
A
SYMBIOTIC
- Host provides source of nutrients and an area to colonise
- Microbes stimulate innate and regulatory immunity, and provide metabolic functions
6
Q
Outline what influences the microbiota.
A
- Microbes encountered during life
- Food
- Medicines
- Personal hygiene
7
Q
Describe viral structure.
A
- Smallest infectious particles (18-600 nm)
- Most are <200 nm - cannot be seen with light microscope
- Viruses contain either DNA or RNA but not both
- Some viral-like particles don’t have detectable nucleic acids
- Parasitic and don’t reproduce independently from host cells
8
Q
Describe the viral protein shell
A
- Viral nucleic acids required. for replication enclosed within protein shell
9
Q
Describe bacterial structure
A
- Prokaryotic
- Cell wall is either Gram-positive (thick peptidoglycan layer) or Gram-negative (thin peptidoglycan layer and overlying outer membrane)
- Some don’t have either of this cell wall and instead survive inside host cells/hypertonic environment
10
Q
Describe bacterial morphology
A
- 1 to 20 micrometres or larger
- Shape varies (e.g spheres, rods, spirals)
- Spacial arrangement varies ( e.g chains, clusters)
11
Q
How can bacteria be identified?
A
- Antibody testing
- Antigen detection e.g PCR
- Bacterial growth requirements
- Shapes
- Gram test
12
Q
Describe fungal structure.
A
- Eukaryotic
- Exist unicellularly (yeast) that replicates asexually or in a filamentous form (mould) that replicate asexually and sexually
- Most exist as either yeast or mould but some assume either morphology i.e dimorphic
13
Q
Describe parasites.
A
- Complex
- All classed as eukaryotes but some are unicellular/some are multicellular
- Range in size from protozoa as small as 4-5 micrometres in diameter to tapeworms that measure up to 10 metres in length
14
Q
What is infection seen as?
A
- A balance between host and pathogen
- Not all bacteria cause disease. Someone with strong immune systems could be ‘infected’ but not suffer from symptoms. Someone with immunosuppressants may suffer
15
Q
What is disease caused by?
A
- Damage produced by the bacteria plus the consequences of innate and immune responses to the infection
16
Q
Define incubation period.
A
- Time required for the bacteria and/or the host response to cause sufficient damage to initiate discomfort or interfere with essential functions
17
Q
What factors influence frequency with which organisms cause disease?
A
- Age
- Epidemiologic factors
- Underlying disease/medication
18
Q
Briefly describe the three types of bacteria.
A
- NORMAL FLORA - cause disease on entering sterile sites of body
- VIRULENT BACTERIA - mechanisms (i.e virulence factors) promote growth in host at expense of host’s tissue/organ function
- OPPORTUNISTIC BACTERIA - take advantage of conditons e.g immunosuppression to grow
19
Q
Describe virulence factors.
A
- Enhance ability of bacteria to cause disease
- Some bacteria release toxins
20
Q
Give examples of virulence factors.
A
- Adherence
- Invasion
- Toxins
- Degradative enzymes
- Cytotoxic proteins
- Induction of excess inflammation
- Resistance to antibiotics
- Intracellular growth
- Superantigens and endotoxins
- Presence of capsules
21
Q
What is the difference between sterilisation and disinfection?
A
- Disinfection is the process of eliminating or reducing HARMFUL microorganisms from inanimate objects and surfaces
- Sterilization is the process of killing ALL microorganisms
