The antimicrobial and antibiofilm activities of copper(II) complexes

Biofilm-related bacterial infections pose a significant problem, as they are generally more tolerant to antibiotics and the immune system. Development of novel compounds with antibiofilm activity is therefore paramount. In this study we have analysed metal complexes of the general structure [M(I_L)(A_L)]^{2 +} (where I_L represents functionalised 1,10-phenanthrolines and A_L represents 1S,2S- or 1R,2R-diaminocyclohexane) and [Cu(I_L)₃]^{2 +}. Antimicrobial activity was tested on a number of bacterial strains, showing that copper(II) compounds were active against both Gram-positive and Gram-negative bacteria, albeit that activity was generally higher for the former. The antibiofilm activity was then determined against a clinical isolate of meticillin-resistant Staphylococcus aureus (MRSA). Strikingly, the copper complexes tested showed significant activity against biofilms, and were better in the removal of biofilms than vancomycin, an antibiotic that is currently used in the treatment of MRSA infections.