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Chapter 2
To summarise, previous authors using the CBR have investigated intralaboratory
reproducibility with a varied number of repeated samples,
methods for enumeration and organisms under examination. The extent of
variation described in the aforementioned research was standard
deviations ranging from 0.06 [117] to 0.655 [123]. In general, the data
suggest that intra-laboratory variation of biofilm density with the CBR is
less than that observed with some other systems. It is important to note
that only one surface material was chosen for each assessment described
above.
2.2. Examining biofilm density and reproducibility using
other biofilm reactor models
In research similar to that described in this thesis, Joseph et al. investigated
the biofilm density of 3 Salmonella enterica serovars in duplicate on
concrete (referred to as cement), plastic (high density polyethylene) and
stainless steel using a microtitre plate system[71]. However the work did
not report the SD or provide any indication if replicate experiments were
performed [71]. The work performed by Joseph et al. is widely used as a
reference for evidence of biofilm formation on contact surfaces and
resistance to sanitizers despite any indication of reproducibility or
robustness of the method used.
Rodrigues et al. investigated total biofilm developed over 48 hours
(measured by crystal violet staining) and viable cells using the plate count
technique [98]. Biofilm density of five S. Enteritidis strains attached to
granite, marble, stainless steel and two types of silestone impregnated
with the antimicrobial agent triclosan were assessed. The results of the
research indicate that the SD varied depending on surface and strain with
the mean ranging from 6-7 log 10 CFU/cm 2 for most surfaces while the SD
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