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Chapter 6
and that the duration of development time does not affect treatment with
disinfectant agents [134, 149].
The research presented in this thesis indicates that under the conditions of
the microtitre plate method, Salmonella biofilm density does not increase
for most strains with extended incubation [134, 149]. However, under the
conditions examined using the CBR, in most cases the density of biofilm
formed increased significantly. Particularly for the S. Agona outbreak strain
S09-0494 and the S. Enteritidis strains S09-0717. Further studies into this
area may have allowed a better understanding into the ability of certain
strains to develop into a more dense biofilm over the extended duration of
time. Further studies may have also aimed to examine if the use of the
microtitre plate is an appropriate method for examining the number of
viable cells or if it is more of a representation of stained biofilm matter
(including dead cells and extracellular material) that may not be an
accurate reflection of increased cell density over time. This may also
provide evidence to indicate the usefulness of comparing the results
achieved by the CBR and microtitre plate methods.
None of the three disinfectants were able to eradicate viable cells from a
168 hour biofilm using the CBR or the microtitre plate method. Studies on
the efficacy of disinfectant agents intended for application in the control of
biofilm should include assessment against an established biofilm, in
particular a biofilm formed over an extended period of time under a
number of different conditions. Development of a biofilm over an extended
period of time on food contact surfaces may contribute to bacterial
contamination of the surfaces, particularly if the disinfectants used do not
eradicate all viable cells as demonstrated in this work.
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