Compounds useful as antibacterial agents are provided. The compounds are analogs of indole-3-carbinol and have a backbone selected from dihydroindolo[2,3-b]carbazole, 2,2′-diindolylmethane, 2′,3-diindolylmethane, and 3,3′-diindolylmethane. The compounds are useful therapeutic and prophylactic treatment of bacterial infections in mammals. Methods of synthesis of the compounds are provided, as are pharmaceutical compositions containing the compounds.