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Chapter 3
S. Enteritidis was a less dense biofilm former than strains of S. Agona and S.
Enteritidis after 48 hours. Interestingly, had the S. Enteritidis strain been
excluded from the work examining biofilm formation over the extended
period of time it may have been assumed that only the S. Agona strain
formed a significantly more dense biofilm on all 5 surfaces than the other
strains of S. Agona and S. Typhimurium. This finding emphasises the
importance of including multiple strains and serovars in biofilm studies.
Furthermore, there may also be use in investigating the density of biofilm
formed by multiple strains within each serovar. As clearly outlined in
section 3.4.3 the S. Agona strain related to the outbreak S09-0494 formed
a more dense biofilm than the S. Agona reference strain SL483 (p=0.004).
This finding suggests that the sole use of only reference strains may be of
limited use in biofilm related studies considering outbreak associated
strains may form a significantly more dense biofilm. Previous authors have
examined biofilm formation of multiple strains and serovars over an
extended period of time using a microtitre plate based system [56, 197].
However, there are also limitations to the use of this method such as
limited surface area. The use of the microtitre plate based method is
discussed in further detail in chapter 5.
Overall, the results presented in this chapter indicate that in most cases
Salmonella biofilm density increases after an extended period of time.
Korber and colleagues also found that S. Enteritidis biofilm increased
marginally in thickness over an extended period of time (72 hours) using a
flow cell device [102]. Similarly, Chorianopoulos also reported that the
density of S. Enteritidis biofilm formation increased over 72 hours [148].
Mangalappalli-Illathu et al. also demonstrated S. Enteritis biofilm density
increased over time (7 days) using a flow cell device [189]. These findings
are broadly consistent with results presented here, although the extent of
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