Antibacterial activity of benzydamine and antibiotic-benzydamine combinations against multifold resistant clinical isolates.

The bactericidal activity of 0.1% benzydamine (CAS 642-72-8, BD), a non-steroidal anti-inflammatory agent was evaluated by the viable count technique against 12 multifold resistant clinical isolates. An efficient rapid activity was obtained irrespective of the antibiotic resistance pattern. Combinations of 0.1% BD and ampicillin, chloramphenicol or tetracycline exerted synergistic bactericidal activity against antibiotic resistant Pseudomonas aeruginosa and Staphylococcus aureus isolates. Using the chessboard technique, out of 114 BD-antibiotic bacteriostatic combinations, 19 were partially synergistic and the remaining were indifferent. The effect of subinhibitory concentrations of BD-ampicillin, BD-chloramphenicol and BD-tetracycline on the growth of the test organisms revealed significant synergism, especially with tetracycline combinations, most likely due to enhanced uptake of the antibiotic by the organisms in the presence of BD.