microbiology: destruction,sterilisation and disinfection of microorganisms Flashcards
define decontamination
Is a combination of processes that removes or destroys contamination so that infectious agents or other contaminants cannot reach a susceptible site in sufficient quantities to initiate infection or other harmful response
define sterilisation
complete killing of all types of microbes including spores
these can turn into spores aka vegetative spores
what is another name for spores
vegetative spores
give examples of eukaryotes
fungi
protozoa
give examples prokaryotes
bacteria eg vegetative ones, spore producing ones
give examples of viruses
herpes simplex virus and hepatitis
what are the methods of sterilisation
heat can be
dry or wet
how do we moist heat something
boiling, autoclaving and exposure to superheated steam at a controlled pressure and temperature cycles
how do we sterilise instruments
using autoclaves is the gold standard
what cycles can we use in the autoclave
115 digress for 30 mins
121 degrees for 15 mins
134 degrees for 3 mins
what type of air displacement method do we use for wrapped instruments
vacuum type b
what type of air displacement do we use for unwrapped instruments
passive type N
how do we check if the sterilisation technique is complete
by a bowie dick test
if the sterilisation test is complete and passed how should the bowie dick test turn out
the square should just be black and white
if the sterilisation test is complete and failed how should the bowie dick test turn out
the square should be black and white with a yellow circle in the middle
what are some cycles we can use for dry heat sterilisation
oven controlled temperature cycles
160-170 degrees for 120 minutes
170-180 degrees for 60 mins
180-190 degrees for 30 mins
what are some disadvantages of the dry heat sterilisation technique
Time consuming method
Slow microbial killing
High temp is not suitable for most materials
which method of sterilisation is more efficient
moist sterilisation is more effective
when might dry heat technique be better than moist heat technology
▪ Such as with metals that can become corroded and sharp instruments
▪ Used for delicate metals which would corrode if used with steam
Or glassware
how do we remove c botulism spores
in the saturated steam environment for 5 mins at 121 degrees
but in a dry hear they need 2 hours at 160 degrees
give examples of chemical sterilisation
using liquid/gas
using ethylene oxide
highly flammable gas mixed with co2 to stop it burning
what is the disadvantages of chemical sterilisation
takes a long time to dissolve from substances
what is the issue with using glutaraldehyde
very toxic
what is the issue with formaldehyde
vapour can reach inaccessible parts
what is the benefit with using formaldehyde
useful for large equipment
how does irradiation sterilise equipment
damage to the DNA and leading to cell death
how does gamma radiation sterilise equipment
cold sterilisation
can go through objects with high efficiency
how does filtration sterilise equipment
Removal of microorganisms in liquid that are destroyed by heat
Used to clarify liquids or gasses
Membrane filters made from nitrocellulose are made with micro pores to effectively to prevent the passage of microorganisms- useful for enzymes which would be denatured with high heat
what is the issue with using chemical disinfection
that bacterial endospores are not killed by this method
what is the issue with using sodium hypochlorite and iodine as disinfectants
Naclo- highly irritant
iodine- less reactive
what do we need to do before we disinfect
clean object
make up the fresh disinfectant
correct concentration
do not mix with other chemicals
what is chemical disinfection limited to
→ Environmental decontamination
→ Antisepsis
Heat sensitive items
define antisepsis
disinfection applied to damaged skin and living tissues
describe sanitation
removal of microbes that pose a threat to public health
which patients are at risk for transmissible spongiform encephalopathies
Symptomatic or at risk
Risk of transmission is through neurological and lymphoid tissues or surgical instruments
Definite, probable, possible CJD
what causes transmissible spongiform encephalopathies
prions
where can prions be transmitted from
dental scalers
dentists hands
