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PY365 Quality Of Sterile Medicines > Sterility Testing > Flashcards

Sterility Testing Flashcards

1
Q

what is killing of microorganisms influenced by

A

a time dependent process influenced by duration of biocidal action and initial bioburden

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2
Q

when can true sterility be achieved

A

can only be achieved after an infinite exposure period

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3
Q

what does a higher bioburden result in

A

results in longer sterilisation times

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4
Q

what is the sterility assurance level

A

probability of a single surviving organism remaining to contaminate a processed product

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5
Q

what is the standard sterility assurance level for pharmaceutical products

A

10-6
- probability of a non sterile unit is 1 in 1 million units processed

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6
Q

what equation can be used to establish the sterilisation process necessary to achieve the SAL

A

IF = No/N= 10^t/D

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7
Q

what are the steps in sterility assurance

A
  1. bioburden determinations
  2. environmental monitoring
  3. validation and monitoring of sterilisation procedures
  4. sterility testing
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8
Q

what is a bioburden

A

the concentration of organisms in a material

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9
Q

what is SAL achieved dependant on

A

dependent on the pre-sterilisation bioburden

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10
Q

outline the benefits of low pre-sterilisation bioburdens

A
  1. reduced exposure of the product to high sterilisation temperatures, minimising degradation of actives and excipients
  2. greater probability of the product passing the bacterial endotoxins test (BET)
    - autoclaving doesn’t destroy endotoxins
    - high bioburden means high endotoxin concentration
  3. shorter autoclaving cycles use less energy
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11
Q

how can the bioburden of pharmaceutical products be determined

A
  1. use of standard microbiological methods
    - pour and spread plates
    - membrane filtration
    application of these methods to raw materials and manufactured medicines may need distinct adjustments
    - due to presence of solid particles, viscosity
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12
Q

what is environmental monitoring

A

where levels of microbial contamination in manufacturing areas are monitored
- microbial numbers should not exceed specified limits

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13
Q

how can microbial load in atmosphere be determined

A

may be determined by settle plates or use of air samplers, which cause a volume of air to be passed over an agar surface

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14
Q

how can contamination on surfaces be measured

A

may be measured using swabs or contact plates

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15
Q

what is measured in environmental monitoring

A

microbial load and contamination on surfaces, including equipment

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16
Q

what is involved in the validation and monitoring of sterilisation processes

A
  1. calibration and testing of all the physical instruments used to monitor the process
  2. evidence that the steam is of desired quality
  3. conduction of leak tests and steam penetration tests
  4. production of data to demonstrate repeatability
  5. comprehensive documentation of all sterilisation aspects
  6. use of biological indictors
17
Q

why are biological indicators used in the validation and monitoring of sterilisation processes

A

sterilisation cycle should be capable of producing an acceptable SAL under worst case conditions

18
Q

describe how biological indicators are used in the validation and monitoring of sterilisation processes

A
  1. standardised bacterial spore preparations
  2. after the sterilisation process, the suspensions or spores on carriers are aseptically transferred to an appropriate nutrient medium
19
Q

what does sterility testing assess

A

assesses whether a sterilised product is free from microorganisms
- can only show that a proportion of the products in a batch is sterile
- provide no guarantee about the sterility status of an entire batch

20
Q

outline the principles of sterility testing

A
  1. placing the product into a suitable liquid culture medium
  2. if, after incubation, there are no signs of microbial growth (measured as turbidity), the item has passed the test
    - counting of colonies is not involved
21
Q

what are the 2 main methods of sterility testing

A

direct innoculation and membrane filtration

22
Q

describe how direct inoculation is used in sterility testing

A
  1. samples are introduced into nutrient media
  2. alternatively, concentrated culture medium may be added to the test fluid in its original container
    - more sensitive test
23
Q

describe how membrane filtration is used in sterility testing

A
  1. recommended by most pharmacopoeias
  2. involves filtration of fluids through a sterile filter
    - pore size of 0.45um
    - filter is transferred into culture liquid media
  3. water soluble solids can be dissolved in a suitable diluent and processed the same way
24
Q

what must be ensured when using conducting sterility tests

A
  1. testing must be performed under aseptic conditions
    - eg. using a laminar airflow cabinet
  2. control tests are necessary to confirm the adequacy of facilities
  3. necessary to use negative controls
    - samples known to be sterile
  4. where an antimicrobial forms part of the product, it must be inactivated before sterility testing
25
Q

name the methods for antimicrobial inactivation in sterility testing

A
  1. specific inactivation
  2. dilution
  3. membrane filtration
26
Q

how can specific inactivation be used for antimicrobial inactivation

A

an appropriate neutralising agent is incorporated into the culture media
- eg. penicillins are inactivated by B-lactamases

27
Q

how can dilution be used for antimicrobial inactivation

A

the antimicrobial agent is diluted in the culture medium to a level it ceases to have any activity
- eg. phenols and alcohol

28
Q

how can membrane filtration be used for antimicrobial inactivation

A

the product is filtered through a membrane filter
- membrane retains any contaminating microorganisms, is washed and transferred to liquid media
- used with antibiotics

29
Q

why are positive controls used

A

it is essential to show that microorganisms will grow under the conditions of the test

30
Q

what does the Pharmacopoeia suggest the use of as positive controls

A

suggests several designated strains as positive controls
- staphylococcus aureas
- pseudomonas aeruginosa

31
Q

outline the limitations of sterility testing

A
  1. destructive test- problem when testing large, expensive or delicate products
  2. procedure intended to demonstrate a negative
    - failure to detect growth could be consequence of using unsuitable media or incubation conditions
  3. no attempt is made to detect viruses
  4. expensive test
    - need clean rooms, equipment and qualified staff
  5. low sensitivity- part of batch is randomly sampled and dependence of sample size
32
Q

give an equation to determine the probability of obtaining ‘n’ steriles in a sterility test involving a sample size of n containers

A

q^n = (1- p)^n

33
Q

when do sterility tests take place

A

take place at the end of the manufacturing process

34
Q

can sterility assurance failures occur

A

they are not uncommon and there are several product recalls each year

PY365 Quality Of Sterile Medicines (19 decks)

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