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Chapter 3
was plated onto TSA for enumeration as previously described (section 2.5
in chapter 2).
3.4. Results
3.4.1. Biofilm Removal
Based on the SEM images it appears that most of the biofilm was removed
from glass followed by tile, while there were more areas of biofilm
remaining attached to steel, polycarbonate, and concrete. Table 3.1
displays the number density of cells recovered from the surfaces following
sonication for 7, 10 and 14 minutes. The results in Table 3.1 suggest that
more cells were recovered from the 5 surfaces after sonication for 7
minutes than after sonication for 10 or 14 minutes. This pattern was
evident for both strains examined (SL1344 and S09-0419). Following these
results, it was determined that whilst the sonication for 7 minutes did not
remove the biofilm completely it did not reduce the number of viable cells.
However sonication for longer durations of time impaired cell recovery as
displayed in Table 3.1. Therefore sonication at 20 kHz for 7 minutes was
maintained as the sonication condition used throughout the work
described in this chapter.
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