The oil of the seeds, petroleum ether and methanol extracts of the whole plant of Cannabis sativa belonging to the family Cannabinaceae were screened for their antimicrobial activity against two Gram positive organisms (<i>Bacillus subtilis</i>, <i>Staphylococcus aureus</i>), two Gram negative organisms (<i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>) and two fungi namely <i>Aspergillus niger</i> and <i>Candida albicans</i> using the cup plate agar diffusion method. The oil of the seeds of Cannabis sativa exerted pronounced antibacterial activity (21 - 28 mm) against <i>Bacillus subtilis</i> and <i>Staphylococcus aureus</i>, moderate activity (15 mm) against <i>Escherichia coli</i> and high activity (16 mm) against <i>Pseudomonas aeruginosa</i> and inactive against the two fungi tested. The petroleum ether extract of the whole plant exhibited pronounced antibacterial activity (23 - 28 mm) against both <i>Bacillus subtilis</i> and <i>Staphylococcus aureus</i> organisms, high activity (16 mm) against <i>Escherichia coli</i> and inactive against <i>Pseudomonas aeruginosa</i> and both fungi. The methanol extract of the whole plant showed also pronounced antibacterial activity (29 mm) against <i>Bacillus subtilis</i>, low activity (12 mm) against <i>Staphylococcus aureus</i> and high activity (16 - 18 mm) against both Gram negative organisms, inactive against Aspergillus niger and low activity (13 mm) against <i>Candida albicans</i>. The minimum inhibitory concentrations of <i>Cannabis sativa</i> methanol extracts of the seeds and the whole plant against the standard organisms were determined using the agar plate dilution method. The standard organisms were tested against reference antibacterial and antifungal drugs and the results were compared with the activity of the extracts

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To evaluate the interaction between plants extract and antibacterial drugs then to confirm the rationale of the ethno-medicinal use of candidate plants. Methanolic extract of Trachyspermum ammi (Fruit), Senna alexandrina mill (Leaves) and Vachellia nilotica spp. nilotica (Fruit) individually and in combination with commonly used antibiotics (ampicillin, gentamycin and tetracycline) were tested by the Cup Plate method in crude for their antibacterial activity against four standard bacterial strains (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa). The highest antibacterial activity was recorded in V. nilotica extracts against S. aureus (IZ = 39 mm) and the lowest antibacterial activity was recorded in T. ammi extract against P. aeruginosa (IZ = 0 mm). When the standard antibiotics were tested, the IZ ranged from 0-31 mm. The lowest (MIC) of the three plants extracts against the standard bacteria were determined, the most potent antimicrobial plant was V. nilotica (MIC<1.156-12.5 mg mLG 1). In synergistic results the three extracts showed synergistic interaction in combination with the tested antibiotics which differed according to the species of bacteria. The Inhibition Zones (IZ) ranged from 0-40 mm. The highest largest IZ of 40 mm was observed against B. subtilis where a combination of V. nilotica and Tetracycline were used. The least susceptible bacteria to the plant extract and combination was S. aureus organisms and the most susceptible bacteria was B. subtilis. The synergy of T. ammi, S. alexandrina and V. nilotica showed an overall increase in the activity of standard antibiotics against standard bacteria, thus, there is a scope to develop effective combinations of such antibiotics and purified forms of these medicinal plants.