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Chapter 4
As discussed previously, Møretrø et al. used the same biofilm model to
examine the effect of disinfectants against S. enterica biofilm [134].
Møretrø et al. found exposure to benzalkonium chloride achieved a ~2
log 10 reduction in S. enterica numbers recovered from biofilm [134]. This is
twice the reduction in the number of cells reported previously by Vestby,
however in this instance it is not clear that the same benzalkonium product
was used by both researchers therefore the difference in disinfectant
product may have contributed to the variation in log 10 reduction achieved.
The product used by Møretrø et al. also included 5-15% acetic acid in the
composition [134]. The disinfectant products chosen by Møretrø et al.
were based on a review of the procedures in place in a number of food
processing environments [134].
Wong et al. evaluated multiple concentrations of benzalkonium chloride in
addition to 5 other disinfectant compounds using the MBEC method [149,
198]. Wong et al. reported that benzalkonium chloride was the least
effective disinfectant against an established (comparators were citric acid
anhydrous, chlorhexidine gluconate, ethanol, quaternary ammonium
compound and sodium hypochlorite [149, 198]. In order to achieve
complete eradication of viable cells Wong et al. used a concentration of
1.5% which is over twice the manufactured recommended concentration.
However, there were also a number of inconsistencies with this work,
Wong et al. found that the number of cells recovered from the surface did
not increase over time [149]. Moreover, Wong et al. found that
concentrations of 1.31, 2.62 and 5.25 g/L of sodium hypochlorite resulted
in no cells recovered from the surface. However, ten-fold higher
concentrations of sodium hypochlorite (26.25 and 52.5 g/L) resulted in a
high population of cells (10 2 -10 4 ) recovered from the surface. Wong et al.
suggested that the low concentration of hypochlorite and the ratio of acidto-protein
may result in oxidative unfolding and aggregation of
proteins[149]. Disruption of cellular proteins in low concentrations of
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