The Destruction of Microorganisms Flashcards
define decontamination
processes that remove or destroy contamination so infectious agents or other contaminants can’t reach a susceptible site in sufficient quantities to initiate an infection or other harmful response
define sterilisation
the complete killing or removal of all types of microorganisms
the 3 basic types of microorganisms
eukaryotes - fungi and protozoa
prokaryotes
viruses
define disinfection
removing or destroying sufficient numbers of potential harmful microorganisms to make an item/surface safe to use
define antisepsis
the practise of using disinfectants to damaged skin or living tissue
define sanitisation
the removal of microbes that pose a threat to public health
how can heat be used in decontamination? which two forms can it be used?
- can either be used in moist or dry form
moist: boiling, autoclave, exposure to steam
dry: oven, controlled temp cycles
which is more effective? moist, or dry heat.
moist
under moist and dry heat, what temp and times can c.botulinum spores be disinfected?
moist: 121° - 5 mins
dry: 160° - 2 hours
what is an autoclave?
a device that uses steam to sterilise
what are the 2 types of autoclaves?
Passive, Type N - for unwrapped instruments
Vacuum, Type B - for wrapped instruments
what are 3 different cycles you can use for autoclaves? temperature and time
115° - 30 mins
121° - 15 mins
134° - 3 mins
what test can you use to monitor the efficacy of autoclaves? what does it ensure and how does it work?
Bowie-Dick Test
- it ensures that all air is properly removed from the sterilisation chamber
how it works:
- use a heat-sensitive sheet
- sheet changes colour when exposed to certain pressures
- positive test that it works = sheet will be uniform in colour, no different colour stains
disadvantages of dry heat
time consuming
energy consuming - higher temps required
may not be suitable for all materials
what are some chemicals that can be used in sterilisation?
gas - ethylene oxide
liquid - glutaraldehyde, formaldehyde
alcohols - methanol, ethanol, isopropanol
chlorine and iodine - e.g. sodium hypochlorite and povidone iodine
what is a side effect of using alcohol for disinfection?
it it dehydrating
can lead to disruption in cell membrane
what caution should be taken with chemical disinfectants?
- clean the object first
- use the chemicals fresh
- use correct concentration
- do not mix with other chemicals
when using chemicals, what should be considered?
- the effect is has on spores
- the corrosiveness
- where it is on the antimicrobial spectrum
how can irradiation be used in decontamination?
- ultraviolet for surfaces
- gamma radiation for pharmaceuticals, medical and dental supplies
what is gamma radiation also known as? how does it work?
cold sterilisation
- can pass through objects with high efficiency
how can filtration be used in decontamination?
it removes microorganisms from liquids that are otherwise destroyed by heat
describe thermal washers
they are good to use for disinfection
- use physical cleaning and thermal biocidal action
which decontamination method is most appropriate in clinical situations?
low risk
- in contact with healthy skin
- not in contact with patients
= cleaning
mid risk
- contact with mucous membranes/body fluid
- contaminated with virulent or readily transmissible organisms
- use on immunocomprimised
= sterilisation or high level disinfection
high risk
- close contact with break in skin
- to introduce into sterile body site
= sterilisation
describe disposable items.
they are single use/single patient
- should be labelled
require sterilisation before use
- usually via gamma radiation
what are Transmissible Spongiform Encephalopathies? Give an example of one.
neurodegenerative disorders
Creutzfeld-Jakob Disease
how is CJD caused, why is it so difficult to treat?
caused by prions in the brain - abnormal infectious protein
- prions are resistant to decontamination
how is CJD infectious?
through neurological and lymphoid tissue
- through dental pulp = low risk
