A group of antimicrobial compounds shows effectiveness for preventing bacterial growth and bio film formation. In particular, the compounds are effective for preventing the growth of gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (“MRSA”) bacteria. The compounds include naturally-occurring compounds such as linoleyl ethanolamide, noladin ether, and anandamide, and man-made compounds such as CP55,640 [(−)-cis-3-[2-Hydroxy-4-(l,l-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol] and O-2050 [(6aR,10aR)-3-(l-Methanesulfonylamino-4-hexyn-6-yl)-6a,7,10,1Oa-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran]. Because these antibacterial compounds have unique modes of action and/or unique chemical scaffolds compared to traditional antibiotics, they are extremely useful against bacteria having resistances to antibiotics.