Product Preservation 2

Question 1

Changes in efficacy of preservatives changes with both ___________ and _________ of biocide

Answer 1

temperature

concentration

Question 2

Generally the ______ the concentration of the biocide
the greater the rate of killing. The important parameter to assess this is the ______ Exponent (or dilution coefficient; η)

Answer 2

higher

Concentration

Question 3

(η) is the concentration exponent. It is a measure of the effect of changes in

Answer 3

preservative concentration on cell death rate.

Question 4

The Concentration Exponent (η) can be determined by measuring

Answer 4

the time needed to produce a comparable level of killing in a bacterial suspension (T1, T2) at two different concentrations of an antimicrobial agent (C1, C2)

Question 5

If the concentration falls by a quarter (is reduced to __% of
the original) then: C1/C2 = 1.00/0.75 = 1.33 i.e. 1.33η corresponds to the increased time factor (T2/T1) to attain the same level of killing

Answer 5

75

Question 6

In another example, if the concentration falls by half (is
reduced to 50% of the original) then: C1/C2 = 1.00/0.50 = 2.00 i.e. 2.00η corresponds to the _____ time factor (T2/T
1) to attain the:

Answer 6

increased

same level of killing

Question 7

Dilution of agents with high η values → marked ________

in time needed for comparable killing effect

Answer 7

increase

Question 8

Dilution of agents with low η values → ___ influenced

Answer 8

less

Question 9

The activity of a preservative (or other antimicrobial agent) usually ______ when the temperature at which it acts is increased

Answer 9

increases

Question 10

How can pH of formulation affect preservative ability?

Answer 10

• changes in the preservative molecule (as for weak acids such as benzoic and sorbic acid at higher pH ranges – ionisation of preservative)
• changes to bacterial cell surface (increased negative charge on cell surface with increasing pH,
  this can enhance binding of positive charged molecules such as quaternary ammonium compounds)

Question 11

Increasing pH can increase ____ charge on bacterial cell surface, enhancing the binding of +vely charged molecules such as quaternary ammonium compounds.

Answer 11

-ve

Question 12

What is the impact of changes in preservative

availability on efficacy?

Answer 12

The concentration of the preservative available to control the growth of microorganisms will be reduced in the pharmaceutical product

Question 13

Different microorganisms
show varying responses and
sensitivity to preservatives and
other antimicrobial agents. Some organisms are intrinsically
resistant to certain antimicrobials,
or may acquire resistance. List the order of these microorganisms from least resistant to most resistant:
- vegetative bacteria
- prions
- bacterial spores
- enveloped viruses
- mycobacteria
- non enveloped viruses
- fungi (yeasts and moulds)

Answer 13

• enveloped viruses (least)
• vegetative bacteria
• fungi (yeasts and moulds)
• non enveloped viruses
• bacterial spores
• mycobacteria
• prions (most)