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Chapter 6
chosen as an appropriate method for investigating the efficacy of
disinfectants against a pre-established biofilm on concrete surfaces.
The results detailed in chapter 4 indicated that using the CBR, sodium
hydroxide was effective at eradicating a 48 hour Salmonella biofilm for the
two strains examined (S. Typhimurium SL1344 and S. Agona SL483).
However, the same concentration of sodium hydroxide was not effective at
eradicating all viable cells from a 168 hour biofilm of the same strains.
Previous research has suggested that Salmonella biofilm density does not
increase substantially over time and that the duration of development time
does not affect treatment with disinfectant agents [56, 149]. Therefore, an
important finding of this research was to demonstrate that age of biofilm
may be important in studies investigating the efficacy of disinfectants
against an established biofilm. When biofilm was formed using the CBR,
there was a reduction in the number if viable cells directly after
disinfection treatment with sodium hypochlorite and benzalkonium
chloride. However, neither of the disinfectants was effective at eliminating
all viable cells from the 48 hour or 168 hour biofilm. This highlights the
need for careful consideration of content and concentration of
disinfectants used for cleaning food processing environments that may be
subject to contamination or presence of biofilm.
As described in chapter 5, when all 13 strains were assessed using a
microtitre plate method, the results indicated that none of the 3
disinfectants were effective at eliminating the biofilm from the surface of
the plate post 48- or 168 hour biofilm formation. This result was
unexpected considering that sodium hydroxide was effective against the
same bacterial strains when examined in the CBR system after 48 hours
incubation. Although there were differences in the test procedures,
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