Green Tea (Camellia sinensis) Extract is Effective Against Biofilms of Staphylococcus aureus and Pseudomonas aeruginosa, and Interferes on the Activity of Antimicrobial Drugs

Background: Given the lack of options for treating infectious diseases, it is urgent to explore new antimicrobials. Plant food historically represents relevant sources of antimicrobial molecules. Objective: Here, we show that green tea can eradicate biofilms and planktonic cells of clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa. Methods: We conducted in vitro antimicrobial activity tests (MIC, MBC, MBEC). Cytotoxicity tests were conducted using BGM cells. We used UPLC and GC-MS to detect flavonoids and other relevant phytomolecules. The antioxidant potential was assessed using the β-carotene bleaching test. The extract was combined to clinically relevant antimicrobial drugs in vitro to investigate possible synergism or antagonism. Results: To the best of our knowledge, MIC values are among the lowest ever described for the alcoholic extract (8 μg/mL). The extract presented elevated antioxidant potential and was not toxic to BGM cells. When the extract was combined to clinically relevant antimicrobial drugs, statistically significant antagonism was frequent for the drugs used against S. aureus isolates, whilst significant synergism was observed for some drugs used against P. aeruginosa isolates. Conclusion: Our data open doors for exploring isolated molecules from green tea extract against bacterial biofilms, and for developing formulations for clinical treatments.