As depicted in Table 5, of the 21 combinations tested between T. saturejoides EOs samples and cefixime, no antagonistic effect was observed while, 14 (67%) showed total synergism, 4 (19%) had partial synergistic interaction, and 3 (14%) had no effect. The best synergistic effect was obtained with the combination of Er-Rich EO (from arid site) and cefixime with FIC index ranged from 0.29 to 0.5. These values are comparable to what has been previously reported on the other members of Thymus genus ( Fadli et al., 2012). Furthermore, the total synergistic effect obtained with this combination was observed for all bacteria, except for E. coli, which was resistant to all combinations tested ( Table 5). This finding is in contrast to that reported by Fadli et al. (2012) on the synergistic effect of cefixime in combination with EOs from other thyme species against the Gram negative E. coli. This discrepancy may be attributed to the chemical composition of EOs and/or the resistance of the strain used in each study. Synergistic interaction, but less pronounced, can be seen when combining EOs from Taws and Ourika populations with cefixime. In fact, both combinations have showed four total synergism (FICI ≤ 0.5) and two partially synergistic effects