Antimicrobial disk susceptibility tests serve as standard assays for measuring the activity of compounds against pathogenic bacteria. In the current study, some plant-derived proprietary essential oil blends (Olea europaea , Pimpinella anisum L. , Coriandrum sativum , Matricaria chamomilla L. , Borago officinalis , Cimum basilicum L. , Cuminum cyminum , Thymus vulgaris thymol , Menta xpiperita L. , Rosmarinas officinalis comphora) were tested for their antibacterial activity against five common strains of pathogenic bacteria using disk susceptibility tests. A formulation intended for topical use (Essential Oil Formulation 1) (EOF1) inhibited the growth of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus as evidenced by zone inhibition diameter measurements when compared to those reported for standard antibiotics. EOF 1 exhibited no activity against Proteus vulgaris and Staphylococcus epidermidis. The second formulation (Essential Oil Formulation 2) (EOF2), intended for inhalation use, inhibited the growth of all five test bacteria strains with zone inhibition diameters two to three times greater than those reported for standard antibiotics. The growth of all five bacteria strains was inhibited when a cotton swab impregnated with EOF 2 was suspended above the bacterial lawn, indicating a true vapor or fume effect by this formulation.