The use of phytochemicals to improve the efficacy of antibiotics

Abstract

With the constant increase in antibiotic resistant bacteria and the lack of sufficient new antibiotics being brought onto the market, alternatives need to be found to cope with infections resulting from these bacteria. One such an alternative is to combine existing antibiotics with phytochemicals to enhance the efficacy of the antibiotic. A group of phytochemicals that is said to have such effects, according to in vitro studies, is essential oils. In vitro studies have shown that essential oil components such as carvacrol, thymol, eugenol, cinnamaldehyde and cinnamic acid in combination with an antibiotic can have a synergistic effect against bacteria. Not all essential oil components are effective with the same combination of antibiotics and bacteria. Several tea tree oils are known for their antimicrobial properties, yet their components have not been studied in combination with antibiotics. The mechanisms through which synergism between antibiotic and essential oil components occur are poorly understood. Several general modes of action have been put forward through which antibiotics and the essential oil components could have a synergistic effect, such as through the inhibition of the antimicrobial resistance mechanisms, but also by affecting multiple targets (e.g. blocking multiple targets in the metabolic pathway). There are still several hurdles to overcome before this type of therapy can be used in the clinic. Not only do more studies need to be conducted on the components of essential oils that show potential, but the mechanisms involved need to be understood and safety aspects of such combinations need to be studied too. A next step towards use in the clinic would then be in vivo studies to predict what will happen in the human situation.