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Chapter 3
3.6. Summary
The research presented in this chapter demonstrates that the density of
cells recovered from an S. enterica biofilm increased over an extended
period of time of 168 hours in comparison to the standardised method of
48 hours recommended for using with the CBR and other methods. The
increase in cell density was also confirmed through the use of SEM.
Secondly, it was evident from the use of SEM and altered sonication
conditions that the biofilm was also more tightly attached to the surface
after biofilm development over the extended period of time.
Previous authors have suggested that biofilm growth is optimized after 48
hours. This could have serious consequences relating to research involving
food-borne pathogens as the research may not reflect real life conditions
where a biofilm may continue to grow over time if undetected.
Previous research in this area has tended to examine a limited number of
strains or a number of strains from the 1 serovar. The research provided in
this chapter suggests that it may be important to incorporate a number of
strains and serovars into studies investigating Salmonella biofilm formation.
Similar to chapter 2, the work presented in this chapter also found that
more cells were recovered from tile than other surfaces such as plastic
which is commonly used in biofilm studies.
However, a key limitation remains evident in the research described in this
chapter as 168 hour biofilm was not fully recovered from the coupons. As a
result, incomplete removal decreases the validity of using a plate count
method to determine the density of biofilm attached to the surface.
Incomplete removal also undermines the use of direct comparisons of the
density of recovered cells particularly between the biofilm recovered after
48 and 168 hours. The SEM images also provide evidence to suggest
differences in the degree of removal of cells from the 5 surfaces after 168
hour biofilm formation.
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