Sterility Flashcards
Fluid Thioglycollate medium
- Direction inoculation method
- high tempt (30-35)
- aerobic and anaerobic
Soya bean casein digest medium
- Direction inoculation method
- low tempt (20-25)
- fungi
Why is prefiltration important?
- there is a risk we dont get all the bacteria
-we can extend the life of the smaller more delicate final filter
-
Explain a depth filter
- compacted polyproplyene/celluose or glass
- can use a vaccum or pressure (35-70 PKa) for uniform POSITIVE pressure
- they are irregular squiggles
- retention depends on normanal pore rate and bacteria sensitivity
What are the disadvantages of a depth filter?
- retains liquid - decrease volume of product
- proteins can be absorbed
- glass can break off into solution
- not 100%
What is the bubble point test?
- testing integrity
- Filter is tested before and after use
- the point where the liquid is forced out of the small filter pores
- filter MUST be wetted first and correct liquid must be used
- smaller filter- more pressure required
gas steriliastion
- alkalying agents
- ethylene oxide
- 5 oxidising agents
- reactive, interact with amino acids, proteins, purine bases
- this is also an alkyaling agent that is assoicated with cytotoxic carinogenic and mutagent effects
- 5 highly reactive, toxic compounds
about ethylene oxide
- cyclic ether
- colourless at room tempt
- liquid at 12 degrees
- > 3% conc = highly flammable
- non-selective (will kill everything)
- can cause oedema, nausea, dizziness, nose irritation, skin eruptions, allergic reactions
- good for rubber, plastic, electrical, equipment
- first order kinetics
Is gas sterilisation effective?
factors affecting this
- for surfaces
- good penetration,
- gas MUST be removed afterwards
- doubling concentration = doubles effect
- > 300mg/L must be used for effectiveness
- each increase of 10 degrees= doubles effect
- MUST have a moist envirnment
- humidy 33%
Aeration of load
air that is added to the system MUST pass through a bacterial-retentive filter of 99.97%
Ionising Radiation sterility
Gamma rays(cobalt 60), X-rays(bombardment with energised electrons), accelerated electrons
- great for sensitive (no not wet or heat products)
- kills all types of things
- used for terminal sterilisation
- used for, plastics, containers, aluminium, biological products, dressings
Isonising: How it works>
- ionisation
- radical formation
- biochemical changes
- breaks DNA strands
- lesions in the nitrogenous bases
standards for Ionisation by BP
terminal sterilidation needs 25 kGy (1 gray = 1 joule of energy)
-sensitive stuff (vegies) = 0.5-10 kGy
moderate(moulds) = 2-40 kGy
-resistant (bacteria) = 10-50kGy
-resistant (virus) = 10-40 kGy
-highly resistant (bacillus spores) = 35-80kGy
what affects ionisation susceptability?
-oxygen: no oxygen more likely for resistance
-mositure:
-temp: hight = decrease D value
-organic substrates = protective effect
chemical
measuring radiation
using a dosimeter
- they are calibrated from supplier
- should be calibrated every year
