Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Lee H. Lee

Committee Member

Chunguang Du

Committee Member

John Gaynor

Abstract

The rise in antibiotic resistant cases has caused a global concern and researchers around the world are trying to find a novel alternative to combat this issue. Green tea with its many health benefits, including antibacterial and antiviral activity, has shown to be one of the most promising candidates to be used as an agent to solve this problem. Green tea commonly found throughout Asia is made from the unfermented leaves of Camellia sinensis and the polyphenols extracted from it can be divided into two categories: (1): Crude, which includes green tea polyphenols (GTP) and lipophilic green tea polyphenols (LTP), and (2): Pure tea polyphenols, which include Epigallocatechin Gallate (EGCG) and lipophilic Epigallocatechin gallate stearate (EGCG-S). All four extracts were used in this study. Twelve antibiotics were selected for this study. Five different bacteria: Gramnegative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), Grampositive Staphylococcus aureus (S. aureus) and Bacillus megaterium (B. megaterium), and Acid Fast Mycobacterium Smegmatis (M. smegmatis) were used. Profiling the effect of four tea polyphenols on 12 antibiotics against five bacteria has been established using a disk diffusion test. Different concentrations of five selected antibiotics and four tea polyphenols on these bacteria were evaluated to select the concentrations achieve LD50. These concentrations were then used for a combination study to determine their inhibitory effect on these bacteria using CFU and microplate assay methods. The Fluoresce microscopic observation and SEM imagery further study the viability and morphological changes. The optimal combination concentrations for E. coli, P. aeruginosa, B. megaterium M. smegmatis is E15 ug / EGCG-S 25 ug/ml, for S. aureus it is Te30 ug / EGCG-S 50 ug/ml. This study suggested that the combination of Erythromycin or Tetracycline with EGCG-S achieves the best antibacterial effect and may be used as a potential therapeutic agent for antibiotic resistant bacteria. Further study using these optimal concentrations to observe their effect on biofilm formation and formed biofilms suggested that higher combination concentrations are needed to efficiently inhibit biofilm. Bioinformatics on four proteins on the bacterial surface suggested that they all have high affinity to EGCG and EGCG-S and support the mode of action that EGCG is inhibiting these proteins.

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