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Chapter 4
coupons were incubated for 24 hours in TSB at 37°C after contact with
sodium hydroxide (10-, 45- or 90-minutes) and neutralized as described.
Thus sodium hydroxide effectively sterilised the coupon with the 48 hour
biofilm.
However, as illustrated in Table 4.3 sodium hypochlorite (500mg/L) and
benzalkonium chloride (0.02%) had little impact on reducing the number of
viable cells recovered after a contact time of up to 90-minutes. The mean
log 10 density of cells recovered from the S. Agona SL483 biofilm was only
marginally less after 10-, 45- or 90-minute of exposure. Following
treatment of the S. Typhimurium SL483 biofilm with sodium hypochlorite
there was just over 1 log 10 reduction in cells recovered from the surface
and less than 1 log 10 reduction in the number of cells recovered was
achieved after 90 minutes treatment with benzalkonium chloride. Similarly,
there was only a marginal reduction in the number of cells recovered from
the S. Agona SL483 biofilm after contact with sodium hypochlorite and
benzalkonium chloride after contact for 10-, 45- and 90-minutes. As
expected there was dense re-growth in the TSB broth in which a whole
treated coupon was placed. For both strains there was an apparent impact
of time of exposure to sodium hypochlorite and benzalkonium chloride in
that there was a gradual reduction in biofilm density following 10 to 45 to
90 minutes of exposure.
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