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Chapter 4
availability of multiple models and recommendations tends to result in
difficulties with the comparability of data from different studies research.
Buckingham-Meyer et al. compared 5 different biofilm test methods. This
work used identical glass surfaces to provide biofilm substratum and used a
standardised biofilm removal and enumeration method throughout
(control coupon–treated coupon). The work evaluated biofilm formation of
two strains of P. aeruginosa and S. aureus [117]. The methods varied quite
significantly in relation to fluid shear and operation system (batch or
continuous flow system). The CDC reactor (as previously described) and a
drip flow reactor model (coupons placed in a vertical line in a reactor vessel
which comes into contact with a flow of inoculated medium) were used.
Other methods included a dehydrated biofilm system (coupons taken out
of CDC reactor and dried in accordance to ASTM standards) and the dried
surface method (heavy inoculum of test organism allowed dry onto the
surface for 2 hours in accordance to the ASTM standards). Buckingham-
Meyer suggested that methods such as the dried surface technique and
static biofilm method resulted in a ~4 log 10 reduction in the number of
viable cells recovered from the surface after contact with sodium
hypochlorite. In contrast, after contact with same disinfectant agent there
was only a ~1-2 log 10 reduction in the number of cells when the biofilm was
formed using the CBR method [117]. This work emphasised the difference
in the apparent efficacy of disinfectant products used against the same test
strains may be greatly influenced by the method applied.
4.1.5. Disinfectants Used
Three disinfectants used for this work sodium hydroxide (1 Mole –M),
sodium hypochlorite (500mg/L) and benzalkonium chloride (0.02%
volume/volume –v/v). The concentrations are based on review of the
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