sterilisation 1 (Dr paul royale)+ sterile vs non sterile( ben forbes)

how does autoclave work?

exposure to dry saturated steam(water vapour) under pressure

what temperature and time is an autoclave usually done for?

121 degrees for 15 mins

how does steam in an autoclave kill microorganisms?

through hydrolysis of proteins like enzymes or nucleic acid

why is autoclave a terminal process?

steam touches the surfaces and heat passes through the product through heat conduction which sterilises the middle of the product too

what is terminal sterilisation?

a sealed bottle in its final packaging is sterile when removed and does not require further sterilization e.g. air filter.

why should there be no air present in an autoclave?

it will lower the amount of steam present which will lower the temperature and pressure, based on daltons law

are porous loads( pippettes)terminally sterlised in an autoclave?

no as air must be reintroduced through a bacteria proof filter

what are some advantages of autcoclaving?

terminal sterilization, kills bacteria and viruses, wide safety margin, cheap?

what are some disadvantages of autoclaving?

only thermostable products can be autoclaved,not suitable to oily preparations like cream and ointmenst

how does an hot air oven work to sterilise

does not contain water so used convection and radiation through high temperatures for longer periods of time

what is mechanism of cell death from dry heat?

oxidative process against proteins and nucleic acids

give an example of product sterilized by autoclave?

products given through the IV route- injectables

what are examples of products that can be sterilised through dry heat?

oily injectables, powders, glassware, metal equiptment prone to rusting

what are some advanatges of dry heat sterilisation?

used for substances that may be harmed by water,less damaging to glass and metal, can be used for assembled apparatus

what are the disadvantages of hot air ovens?

not suitable for packaging material like plastic/rubber, surgical dressing. not a terminal process as things need to be repackaged.

what is the mechanism of cell killing for ethylene oxide?

alkylation which disrupts the chemical function of the proteins and nucleic acids

what products would be sterilized using ethylene oxide?

single use medical devices like catheters, pacemakers wires

what are the advantages of using ethylene oxide?

use of low temperatures damages fewer materials, good penetration into porous loads and plastics, effective against all microorganisms

what are the disadvantages of ethylene oxide

there must be no residue of ethylene oxide as it is toxic,not a terminal process and requires repacking, slow and lengthy process,more expensive, gas is flammable so needs to be in a mixture

what is the source of radiation in sterilisation?

cobalt 60

what is the mechanisms of killing from using radiation as sterilisation?

production of radical which damage DNA

what are the advantages of radiation?

terminal process, very efficient, effective against many microoganism, can be used for thermo unstable products

what are some disadvantages of radiation

not effective against some viruses and prions, expensive, dangerous and perceived side effects

what is UV used to sterilise?

water

what is the smallest size a filtrate can filter out?

0.22 micro meters

what type of filter is most commonly used?

screen filter

what are the advatnages of filtration?

good for thermolabile products,moves bacterial bodies including endotoxins and LPS

what are the disadvantages of filtration

not suitable for suspension, not a terminal process, requires a sterility test, viruses and mycoplasms not removed

what is an example of a product that sterilsied using radaition?

insulin

what function groups have strong smells that can indicate product spoilage

hydrogen sulfides, amine, fatty acids

what are some examples of API that can degrade?

alkaloids like atropine, morphine, penicillin, hydrocortisone

what excipients in a formulation can microbes break down to get energy?

suspending agents, thickening agents, surfactants

what preservative can be degraded by psuedomonas

phenol

how can we alter the water content of a formulation to reduce microbial growth?

exploiting the osmotic pressure by adding alot of solutes like sugar to reduce the water activity

what water activity allows good microbial growth?

0.98

what pH range do bacteria thrive?

4-8

how does surface tension effect microbial growth?

low surface tension encourages the growth of gram negative bacteria