Synergism of flavonoids with bacteriostatic action against Staphylococcus aureus ATCC 25 923 and Escherichia coli ATCC 25 922.

In our previous studies, bacteriostatic action of flavonoids against Staphylococcus aureus ATCC 25 923 and Escherichia coli ATCC 25 922 was demostrated. In the present work synergism of their combinations in order to improve the bacteriostatic action against the same microorganisms was determined. The experiences were made in nutritive broth, maintaining constant one drug concentration (20 microg/ml) and increasing the other one. A turbidimetric kinetic method was used and by means of a mechanism previously proposed, the minimal inhibitory concentrations (MIC's) of each flavonoid combination were determined. The MIC's for assayed combinations against S. aureus were: variable morin - constant rutin: 157.44 microg/ml and variable quercetin - constant morin: 29.9 microg/ml. The values obtained against E. coli were: variable morin - constant rutin: 78.5 microg/ml; variable quercetin - constant rutin: 47.4 microg/ml; variable quercetin - constant morin: 25 microg/ml; variable morin - constant quercetin: 27.4 microg/ml.