Studies on the antibacterial activity of phanquone: chelating properties in relation to mode of action against Escherichia coli and Staphylococcus aureus.

Phanquone is active against a wide range of Gram-positive and Gram-negative organisms. Its activity is affected by the nature of the suspending fluid, pH and anaerobic growth conditions. Its ability to chelate metal ions was examined and found to be related to its antibacterial activity, which was reduced by the presence of added metal ions, e.g. Co (II), Cu(II), Fe(II) and Fe(III) in nutrient media for both E. coli and S. aureus. When antibacterial activity was examined in dis-nutrient media for both E. coli and S. aureus. When antibacterial activity was examined in distilled water, then certain added metal ions, whilst antagonizing activity was examined in distilled water, then certain added metal ions, whilst antagonizing the activity of Phanquone against E. coli, exerted a co-operative effect in the case of S. aureus. The addition of EDTA and NTA lowered the activity of Phanquone against S. aureus, but not E. coli, while the addition of thiol-containing compounds lowered its activity against E. coli but not S. aureus. concentration quenching was observed for S. aureus but not for E. coli, while overnight pre-incubation at 4 degrees C resulted in the appearance of a growth zone inside the zone of inhibition in the case of S. aureus but not E. coli. Phanquone may have a different mode of action against the two organisms.