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Chapter 2
facilitates testing of different disinfectants at varied concentrations on
coupons that carry biofilm which has developed under uniform conditions
[117]. Previous authors have also demonstrated that the CBR results in a
more dense biofilm and a smaller log 10 reduction after contact with
disinfectant agents than other methods such as drip flow reactor or the
current standard of assessing the efficacy of a disinfectant against a
microbial suspension attached to a surface (EN13697:2001) [117]. The
European Committee for Standardisation (CEN-Comité Européen de
Normalisation) EN13697:2001 and other current standards are described in
greater detail in chapter 4. It is possible that the larger surface area
provided by the coupons in the CBR in comparison to other biofilm reactor
models such as the microtitre plate based system may be responsible for a
more dense biofilm formed on the surface over the allocated period of
time [165]. The use of multiple surfaces and provision of a larger surface
area exposed to nutrient flow and mixing or shear stress may also be more
representative of the conditions found in food processing.
However there are also a number of disadvantages to the CBR. Firstly, the
CBR is designed for batch-flow and continuous flow provision of sterile
media to optimize biofilm development. Therefore, given the size of the
reactor and the flow rates chosen (0.5-11ml minute -1 ) a large quantity of
media is required to achieve the biofilm development over the continuous
flow period. For a flow rate of 1ml minute -1 over 7 days over 14 litres of
fresh media is required. The process of replenishing supply of sterile media
also allows opportunity for contamination unless strict aseptic techniques
are applied. Therefore the CBR is costly and time consuming in comparison
to other methods that can use a 10/100 fold less quantity of test chemical
per experiment such as the MBEC method described in chapter 1.
Performing disinfectant assays using the CBR requires more handling of the
substrata and materials such as sterilized tweezers, glass containers,
pipettes, syringes and plates whereas the use of a microtitre plate method
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