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Chapter 4
presented in this thesis that found that the density of biofilm cells
continued to grow up to 168 hour, as discussed in chapter 3. Moreover, the
work presented in this chapter also demonstrated that the age of a biofilm
had an important impact on the log 10 reduction achieved by all three
disinfectants.
Using the Calagary biofilm device (MBEC TM ), Wong et al. reported that the
age of a Salmonella biofilm did not result in increased resistance to
disinfectants. Wong et al., found that in most cases there was a larger log 10
reduction in cells after contact with disinfectants in the 7- day biofilm when
compared to a 3- and 5- day biofilm [149]. However, as previously
discussed in chapter 3, the model used by Wong et al. to study biofilm
growth studied may not support extended biofilm growth possibly due to a
smaller surface area available. Therefore, it may be possible that the extent
of biofilm reduction may not reflect conditions found in real life scenarios
where biofilm cells continued to grow over a longer period of time. This
may have serious implications for reporting the level of activity of
antimicrobial agents. It is also important to note that in most instances the
concentration necessary to reduce the cell numbers above the >4log 10
threshold was also above the concentration recommended by the
manufacturer.
4.4.5. Variability in methods
The lack of standardization of methodology for most biofilm research
results in difficulty to compare studies. As demonstrated in the discussion
of the results in this chapter, there is limited comparability between this
research and previous research due in a large part to variation in methods.
Moreover, there is evidence of limited comparability of some research
reported using the same research methods, disinfectants and similar
strains within a single research group [113, 134]. The ASTM standards
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