The antimicrobial activity of (-)-epigallocatehin-3-gallate and green tea extracts against Pseudomonas aeruginosa and Escherichia coli isolated from skin wounds

Background: Skin infections with Gram-negative bacteria are sometimes challenging to treat, because these bacteria show multidrug resistance against commonly used antibiotics and patients with Gram-negative bacterial infection overall have deteriorated in conditions in many cases. Studies have shown that epigallocatechin gallate (EGCG) and green tea extracts (GTE) inhibit the growth of several Gram-positive bacteria species. Objective: The purpose of this study was to investigate the minimum inhibitory concentrations (MICs) of EGCG and GTE in Pseudomonas aeruginosa and Escherichia coli, and assess the use of these chemicals as an alternative or adjunct topical antimicrobial agent against P. aeruginosa and E. coli with multidrug resistance. Methods: The MICs of EGCG, GTE, and other tested antibiotics were measured and compared to determine the antibacterial efficacy and the differences in pattern of resistance. Results: The P. aeruginosa and E. coli strains used in this study showed multidrug resistance. EGCG inhibited the growth of P. aeruginosa at a MIC level of 200-400 μg/ml. The MIC of GTE was a 1:16 dilution for P. aeruginosa. EGCG showed antimicrobial activity against E. coli at a MIC of 400 μg/ml. In the case of GTE, the MIC was a dilution between 1:8 and 1:4 for E. coli. Conclusion: EGCG and GTE showed potential as alternative or adjunct topical antimicrobial agents for infections that are resistant to traditional antibiotic therapy.