3.4. Antimicrobial Properties

The MIC values of 1,4-bis-[N-(1-alkyl)-N,N-dimethylammoniummethyl]benzene dibromides (from 4 to 18) against bacteria and microscopic fungi (yeast and molds) were measured at the Institute of Fermentation Technology and Microbiology, Technical University of Lodz in Poland. The MICs are defined as the lowest concentration of the compounds at which there was no visible growth of microorganisms. MIC values were determined by a standard tube 2-fold dilution method [29]. The experiments were carried out on the Gram-positive bacteria: Staphylococcus aureus ATCC 6538, Bacillus subtilis NCAM01644, Gram-negative bacteria: Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 85327, yeast: Candida albicans ATCC 10231, and molds: Aspergillus niger ATCC 16404, Penicillium chrysogenum ATCC 60739. Antifungal properties were checked on a Malt Extract Broth medium (Merck, Darmstadt, Germany) at a density of inoculum of 1–2 × 10⁶ cfu/mL; antibacterial activity—on Trypticase Soy Broth (Merck), density of inoculum 1–2 × 10⁷ cfu/mL. All tests were repeated three times.