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Chapter 5
was formed at room temperature, the results suggested that the outbreak
strains of S. Agona S08-0601 formed a more dense biofilm than other
strains of S. Agona, S. Typhimurium and S. Enteritidis studied. However
there appears to be relatively little difference between the mean OD 590 of
the stained biofilm when the strains were incubated at 37°C. When the full
set of OD 590 measurements were examined (Appendix 2-Table 2 and Table
3), the difference in mean was largely due to the impact of a small number
of outlying values on the mean OD 590 for the S. Agona S08-0601 strain. If
those outliers were excluded there appeared to be only a marginal
difference in the OD 590 measurements of biofilm formed by the two
outbreak strains. Similarly, there were only marginal differences between
the S. Agona strains related to the outbreak and the other S. Agona strains
(not associated with the outbreak).
However, when the biofilm was formed at 22°C in most instances, the S.
Agona strains formed a more dense biofilm than the S. Typhimurium and S.
Enteritidis strains. This observation is displayed the ranking of strains based
on the highest mean OD 590 (1) to the lowest OD 590 (13). Based on this, 5 of
the 6 S. Agona strains display the highest mean OD 590 measurements.
Although as previously discussed, the variation in repeated measures (as
displayed in Appendix 2-Table 2 and Table 3) needs to be considered when
making direct comparisons of mean OD 590 of strains. However the trend for
S. Agona to form a more dense biofilm than S. Enteritidis and S.
Typhimurium is not consistent when the biofilm was formed at 37°C.
Similarly, there were differences between the strains within the S.
Typhimurium serovar when incubated at 22°C, particularly for the S.
Typhimurium strain SL1344, but again there were a small number of
outliers in the 9 observations of SL1344 (Appendix 2- Table 2 and Table 3).
The presence of outliers in the set of measurements of OD was also
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