Sterilisation

• What does it mean to produce a sterile product under 'clean' conditions?

  To produce the product in an environment with a low microbial count.
• What is the process used to produce sterile products?


  Aseptic processing
• Define what is meant by sterile


  Free of viable microorganisms.
• Define sterilisation


  The process of killing all viable microorganisms.
• What are viable microorganisms?


  Microorganisms which cause harm.
• Give one method of removal of contaminants


  Filtration
• Give 3 destructive methods for sterilisation


  • Heat (moist OR dry)
  • Ethylene oxide (chemical sterilisation)
  • Radiation
• What is process validation?

  Testing a sterilisation process to ensure that it functions by testing it against the most resistant forms of microorganisms.
• What are resistant microorganisms also referred to as?

  Biological indicators.
• What are biological indicators?

  Organisms used to monitor environmental conditions.
• Describe filtration

  Passage of a fluid across a filter to remove any contaminating solutes.
• What are the 2 types of filters?

  Depth & screen.
• What is the main difference between depth & screen filters?

  Depth filters are non-fixed pore sizes, whereas screen has a uniform pore size.
• What is a disadvantage of depth filters?

  They rely on inertial impaction - have to apply pressure to push filtrate through.
• Compare depth with screen filters


  -

  
• What is an asymptote curve?


  A curve that a function approaches but never touches.

  
• How can we calculate death rate?

  Do semi-log of the kill curve to turn it into a straight line. Measure gradient to calculate the death rate.

  
• What is a kill curve?

  Graph showing effectiveness of sterilisation techniques over time.
• What is the D-value

  The decimal reduction time - time taken at a fixed temperature to reduce the population by 90% (1-Log).
• What does a large D-value mean?

  The higher the number the more resistant the microorganisms are.
• D-value on a graph

  
• What does SAL stand for?

  Sterility assurance level.
• What is SAL value?

  10^-6
• What does SAL do?

  It is a value which represents sterility. It's impossible to get 0 on a log scale so we use SAL.
• Give an example of SAL

  For every 1,000,000 bottles of saline if 1 is contaminated then the batch is safe, if 2 are contaminated then the whole batch is contaminated as it's more than 10^-6.
• What is moist heat in the form of?

  Steam
• How does moist heat kill microorganisms?

  Death by protein coagulation (lose their structure) & hydrolysis.
• How does dry heat kill microorganisms?

  By oxidative processes which can break down cellular components by removing electrons.
• When is moist heat used?

  In aqueous products.
• When is dry heat used?

  In dry powders.
• When is an autoclaver used?

  For moist heat sterilisation.
• How does an autoclave work?

  An autoclave works by using high pressure & steam to sterilise objects. The steam is generated by heating water in a sealed chamber, creating a high-pressure environment which kill microorganisms.
• What is ethylene oxide used for?

  Chemical sterilisation.
• How does ethylene oxide kill microorganisms?

  Alkylates the sulphhydryl, amino, hydroxyl & carboxyl groups on proteins & nucleic acids.
• What is the lethality ethylene oxide affected by?

  Concentration, temperature and relative humidity.
• True or false: Biological indicators are unnecessary when using ethylene oxide as it has many target sites.

  False
• List quality assurance tests:

  • Bioburden estimation
  • Test for sterility
  • Test of sterility
  • Test for pyrogens (LAL)
• What is a bioburden estimation?

  Quantifying the number of microorganisms on a surface or in a sample.
• What is a test for sterility?

  Testing for the absence of microorganism at the end of the test.
• What is a test of sterility?

  Performed on devices exposed to a fraction of the specified sterilisation process - performed during validation.