Bacterial resistance to currently available antibiotics and its rapid increase is a worldwide concern. It is an even bigger problem since this resistance is not often restricted to a specific antibiotic, but generally extends to other compounds of the same class; therefore the need is urgent to develop new antimicrobial agents or new ways to treat the resistant microorganisms. Plants are inexhaustible source of natural antimicrobial compounds that have been found to be "synergistic enhancers" and this enables the use of the antibiotic when it is no longer effective by itself during therapeutic treatment.
The aim of this study was to determine the effect of combined application of Rosemary (Rosmarinus officinalis L.) ethanolic extract by its sub-inhibitory concentration with known antibiotics against different pathogenic isolates using disk diffusion method.
The results showed that the crude extract led to different effects (synergism, antagonism and indifference) on antimicrobial activity of the tested antibiotics. Synergistic effect was seen in most tested bacteria (63.33%), indifference effect was (26.67%) and antagonism effect was (10%) in tested isolates. These results signify that Rosemary extract potentiates the antimicrobial action of antibiotics, suggesting a possible utilization of this herb in combination therapy against pathogenic organisms.