Microbiology Flashcards
(34 cards)
What is a pathogen?
A harmful organism
What is a commensal?
An organism which is part of the normal flora
What is an opportunistic pathogen?
An organism that will probably only cause infection in an immunocompromised individual
What is a contaminant?
An organism that has got into a culture by accident
What is pathogenicity?
The ability of a microorganism to produce disease
What is virulence?
The degree of pathogenicity of an organism
(how easily it can cause disease)
What are the two types of fungus?
Moulds
Yeasts
Describe the structure of moulds
Complex structure, produce
spores (spread in air currents)
hyphae (invade organic tissue)
How do yeasts reproduce?
Single cells which reproduce by budding
Can fungi be killed by antibiotics?
No
their cell wall is different from that of bacteria
special anti-fungal drugs are required
Which type of fungus is the most common cause of mould infection in humans?
Aspergillus spp
Usually affected the immunocompromised
Doesn’t stain with Gram.
Which organism is the commonest cause of fungal infection in humans?
Candida spp (yeast)
Stains a large Gram +ve oval structures that replicate by budding (not binary fission)
What are general features of parasites?
Vary in structure from single-celled (protozoa) to much more complex organisms
Complex interaction with host - life cycle
Give some examples of parasites
Giardia
Schistosoma
What is sterilization?
Destruction and removal of 99.9% of micro-organisms and spores
Used for dressings, surgical instruments - anything coming in contact with normally sterile area of the body
May not inactivate prions
Give four methods of sterilization
Autoclaves - steam under pressure
Dry heat in oven at 160C for over an hour
Exposure to ethylene oxoid gas
Gamma-irradiation
What is disinfection?
Removal or destruction of pathogenic micro-organisms enough to make an item safe
Used for medical equipment that doesn’t need to be sterile
Used for hands, patient’s skin (antiseptics)
What methods can be used for disinfection?
Hot water
Chemicals - bleach, chlorhexidine, povidone iodine
How is fever defined?
Temperature over 38C
How is fever produced?
Antigen/endotoxin interacts with macrophages
cytokines released into bloodstream
cytokines travel to anterior hypothalamus
anterior hypothalamus releases Prostaglandin E, increasing body’s thermal set point
Body perceives it is cold and starts to shiver to conserve heat
What is sepsis?
Small blood vessels become leaky and lose fluid into tissues
Hypovolaemia means that heart has to work harder to maintain oxygenation
Poor tissue perfusion - blood supply to skin, kidneys, liver is shut down
Blood clotting activated - uses up clotting factors - increased risk of haemorrage
What are the 5 ways infection can spread?
Inhalation
Ingestion
Inoculation
Mother to Infant
Intercourse
What is the chain of infection?
Pathogenic microorganism
Reservoir
Means of escape
Mode of transmission
Means of entry
Host susceptibility
What are the three types of infection control precautions?
Contact precautions
Droplet precautions
Airborne precautions
