The most active extract (ME), as revealed by the well assay
above, was used for determining MIC using the agar dilution
method (Oussalah et al., 2007; Ocheng et al., 2014). Two-fold dilutions
of the ME extracts (filtered sterilized, 0.45m filters) were
added to sterilized and tempered NA (50 ◦C) to final concentrations
ranging from 0 to 10mg/ml. The solvent (M)was used as blank. Agar
plates were spotted (5 spots/plate) with 5l of prepared cultures
(106 cfu/ml). Spotted plates were left to dry under ambient conditions
followed by incubation at 35±1 ◦C for up to 48 h. MIC was
defined as the lowest concentration of ME required for complete
inhibition (no visible colonies) of a test organism. Chloramphenicol
and ferulic acid (Carl Roth, Germany) were also used and under
the same conditions. The experiment was done in triplicates.