Carotenoids and flavonoids can impair the effectiveness of some antimicrobial drugs against clinical isolates of Escherichia coli and Staphylococcus aureus

Patients are taking more control over their health, and attracted by contributions to human nutrition, the use of phytonutrients raised. Carotenoids and flavonoids are among the most studied and consumed chemical entities in this sense. However, patients are often unaware of the potential risks associated to drug-herbal interactions. In this study, four drugs were tested combined to lycopene, beta-carotene, resveratrol and rutine in an in vitro model against clinical isolates of E. coli and S. aureus. Statistically significant antagonism was detected within most of the tested interactions for at least one isolate. Few events of synergism were detected. For E. coli, the antimicrobial activity of Cephalexin and Amoxicillin was significantly reduced. For S. aureus, strong reduction of the antimicrobial activity was seen for all drugs. Our data suggest that there might be risks of impairment of the antimicrobial activity of these drugs if co-administered with the tested phytonutrients. Further complementary in vivo studies are needed for full assessment of the biological effects of these interactions. (C) All Rights Reserved