Caffeine as a novel quorum sensing inhibitor / Siti Nur Maisarah Norizan

Siti Nur Maisarah, Norizan (2017) Caffeine as a novel quorum sensing inhibitor / Siti Nur Maisarah Norizan. Masters thesis, University of Malaya.

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Abstract

Quorum sensing (QS) is a system used by bacteria to control the gene expression in response to cell density. QS involves in the regulation of variety bacterial physiological functions such as biofilm formation, pyocyanin production and swarming which has been recorded to contribute to bacterial pathogenesis. Therefore, QS would be an interesting target to attenuate pathogens for treating bacterial pathogenicity and infections. In this work, the anti-QS activity of caffeine; a natural occurring alkaloid found at varying quantities in seeds, leaves and fruits of some plants were tested against Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PA01. Quantification assay on the violacein produced by C. violaceum CV026 showed that caffeine inhibited violacein synthesis in concentration dependent manner. In agreement to that, qualitative studies of C. violaceum CV026 showed the extent of violacein reduction is approximately 68% for caffeine applied at the concentration of 0.3mg/mL. Subsequently, this study also showed that caffeine inhibited swarming motility of P. aeruginosa PA01 as observed by the reduction of P. aeruginosa PA01 migration distance from the spot-inoculated centre on the swarming agar. In addition, caffeine also inhibited P. aeruginosa PA01 pyocyanin production. Qualitative study conducted on P. aeruginosa PA01 has confirmed that P. aeruginosa PA01 pyocyanin production was reduced up to 77% when treated with caffeine at 0.3mg/mL. To the best of our knowledge, this is the first documentation providing evidence on the presence of caffeine anti-quorum sensing activity. This study will allow caffeine to be explored as an alternative for anti-infective drug in future.

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