2.7 Minimum Inhibitory Concentration (MIC) by
broth macrodilution method
The estimation of MIC values of the extracts were
carried out by two-fold serial dilution method. The inoculum
of bacteriawas prepared by diluting the overnight bacteria
culture in brain heart infusion (BHI) broth to a level of
108-109 cfu/ml (OD600 = 0.5). The extracts were prepared
the initial concentrations by dissolving in 10% DMSO and
then serial two-fold dilutions were made in a concentration
range from 50 to 0.195 mg/ml with BHI in tested tubes.
Then, 0.5 ml of the inoculums of tested strains was added
in each tube, mixed on a vortex for 20 s and incubated at
37oC for 24 hours. Control samples were performed
without adding the plant extract. The MIC was taken as
the lowest concentration that inhibited the growth of the
test microorganism after 24 hours of incubation (23).