2.3. Validation of impedance method
To validate the impedance method, cultures of each strain with
random concentration were enumerated by the respective calibration.
The actual cell numberwas again determined by plate counting. The calibration
was validated by the consistency of the two values (impedance
count vs plate count).
2.4. Biofilm development
ERL10460 and ERL104253 are biofilm formers. In order to develop
biofilms of these two stains, the annular rotating disc reactor was used
(Biosurface Technologies Ltd). In the annular reactor, six stainless steel
coupons were fitted into a Teflon holder containing a magnetic stir bar
in the base. This assemblywas autoclaved before being placed on amagnetic
stirrer. Inoculum (4ml) obtained froman overnight culture in TSB
grown at 25 °C were inoculated into each biofilm reactor containing
400 ml TSB and incubated at 25 °C for 24 h with a rotating speed of
150 rpm to generate biofilms.
2.5. Comparison between the impedance method and the bead-beating
recovery technique for the detection of biofilm cells of Y. enterocolitic