Measurement of antimicrobial activity 3 (Part 2)

Question 1

Define sterile.

Answer 1

The COMPLETE absence of life. Absence of prions is desired but difficult to demonstrate.

Question 2

Name some products that need to be sterile.

Answer 2

• injections
• ophthalmic preparation
• dialysis solutions
• implants
• certain surgical dressings
• surgical instruments e.g. syringes, rubber gloves, needles, catheters

Question 3

What is terminal sterilisation?

Answer 3

When you make the product under non sterile conditions using non sterile ingredients and then sterilise it at the end of the process

Question 4

What is aseptic manufacturing?

Answer 4

When you make the product under sterile conditions using sterile ingredients

Question 5

Sterilisation process concentration on the destruction or physical removal of all microorganisms in a product. The processes are designed to remove the most problematic microorganisms (e.g. the smallest bacteria in filtration processes or the most heat- resistant bacterial spores in heat sterilisation). WHY?

Answer 5

This principle is that the elimination of the most problematic species will have led to the elimination of all less resistant microorganisms

Question 6

The choice of sterilisation method is determined largely by the ability of the product to ______ the physical stresses applied during the process such as:

Answer 6

withstand

• elevated temperature (autoclaving, dry heat)
• irradiation
• reactive gas (ethylene oxide)
• filtration (using MO proof filter)

Question 7

What is the simplest sterilisation method? And what are the conditions? e.g. temp + duration

Answer 7

moist heat sterilisation

121 degrees for 15 minutes

Question 8

The choice of sterilization method depends on the _________ of the product

Answer 8

thermostability (e.g. moist heat sterilisation can only be applied to drugs that are heat-stable in aqueous solution and are not subject to hydrolysis)

Question 9

If standard moist heat cannot be used, what is a suitable alternative?

Answer 9

Filtration in combination with aseptic processing

Question 10

Is aseptic processing the same as sterilisation?

Answer 10

NO! Aseptic processing by itself is not a method of sterilisation, rather of preventing contamination

Question 11

What are suitable reference organisms for testing sterilisation efficiency? Give examples

Answer 11

The most durable bacterial spores

• Geobacillus stearothermophilus - formerly known as Bacillus stearothermophilus - for moist heat
• certain strains of Bacillus subtilis for dry heat and gaseous sterilisation and
• Bacillus pumilus for ionising radiation)

Question 12

READ

Answer 12

• Sterilisation processes are usually based on the ability to deal with a ‘worst case’ scenario
• It is usually assumed that organisms within the
  products are no more resistant than the reference spores or isolates (however, resistance may be altered or lost entirely by laboratory subculture; resistance characteristics of the reference strains must be regularly checked)

Question 13

D value is the

Answer 13

resistance of an organism to a sterilising agent. It is also used to indicate the rate of kill (but it does not quantify the amount of microbial killing)

Question 14

What quantifies the amount of microbial killing?

Answer 14

inactivation factor

Question 15

In terms of survival 10^-2 spores/ml means how many survivors in how man ml?

Answer 15

1 survivor in ever 100 ml of liquid

Question 16

Z value represents

Answer 16

the increase in temperature necessary to reduce the D-value of an organism by 90%

Question 17

The elimination of viable microorganisms from a product is a _________-dependent process

Answer 17

time (influenced by duration of biocidal action and initial bioburden)

Question 18

For pharmaceutical products, the most frequent standard is that the probability of a non-sterile unit is 1 in 1 million units processed (i.e. 10^ -6). SO for an initial burden of 10^2 spores, an IF = ____ will be needed to achieve the sterility assurance of 10^-6

Answer 18

10^-8

• The sterilisation will need to produce sufficient lethality to get an 8 log reduction in viable organisms
• Will require exposure of the product to eight times the D-value of the organism (i.e. IF = No/N = 10t/D; so 10t/D = 108; so t = 8 x D)

Question 19

Bioburden is

Answer 19

the concentration of microorganisms in a

material

Question 20

Contamination on surfaces, including equipment, may be measured using

Answer 20

swabs or contact plates

Question 21

Microbial load in the atmosphere may be determined

by use of ‘_____ _____’ or by use of air samplers

Answer 21

settle plates

Question 22

What are some difficulties of sterility testing?

Answer 22

• need trained operators
• need media that can grow a wide range of microbial contaminants
• hard to demonstrate a negative
• difficult eliminating antimicrobial activity