2.9. Microscopic visualization of biofilm
Inhibition of biofilm formation was evaluated by microscopic
technique as described by Chaieb et al. (2011) with minor modifications.
Briefly, biofilm of each bacteria strain was separately performed
(as described above) on round cover glass slides (diameter
1 cm) placed in 24-well polystyrene plates 4 h before addition of
essential oil or plant extract (Greiner Bio-One, France), following
4 h incubation supplemented with coriander and anise oil (at MIC)
with high antibiofilm activity against E. coli and S. aureus, respectively.
DCM of coriander and peppermint (at MIC) with low antibiofilm
activity were applied against E. coli and S. aureus
respectively. Negative and positive controls were performed as
described above, then incubated for 24 h at 37 C and stained with
1/20 Giemsa (Sigma, Switzerland) solution (v/v) for 20 min at room
temperature. Stained glass pieces were placed on slides with the
biofilm on top of the glass slide. Biofilms were evaluated and
confirmed by light microscopy at 100 magnification.