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Chapter 5
with a 0.05% concentration of sodium hypochlorite and 0.02%
concentration of benzalkonium chloride after biofilm development. The
effect of furanone was assessed by measuring the optical density of biofilm
formed on a microtitre plate, while the effect of the disinfectants on the
established biofilm was measured through the use of plate count method
[113]. The results indicated that pre-exposure to furanone increased the
efficacy of the disinfectant agents. There was a ~2 log 10 difference in the
number of viable cells recovered following treatment with furanone and
sodium hypochlorite in comparison to the disinfectant alone. There was
also a ~1 log 10 difference in the number of cells recovered following
treatment with furanone and benzalkonium chloride compared with the
benzalkonium chloride alone [113]. However, even the combined
treatment with furanone and sodium hypochlorite only reached a 4 log 10
reduction (log 10 density of biofilm recovered from the untreated surface–
log 10 density of biofilm recovered from the treated surface) for 1 of the two
strains of S. Agona examined [113]. Moreover, it is important to note that
none of the agents used by Vestby et al. completely eliminated all viable
cells from the biofilm [113].
Against this background the objectives in this chapter are to firstly examine
if dense biofilm forming potential can be predicted using congo red agar
and if this method can be used as an appropriate screening method to
identify dense biofilm forming strains. Secondly, to investigate the use of
the microtitre plate method to examine biofilm density of S. enterica
strains and the ability of the strains to withstand disinfectant treatment
using a microtitre plate based method.
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