Evaluation of anti-quorum sensing potential of Averrhoa bilimbi (Kamias) against Pseudomonas aeruginosa ATCC 27853

Abstract

Background & Objective: Many opportunistic and nosocomial pathogens like Pseudomonas aeruginosa are very reliant on a bacterium-to-bacterium communication system called quorum sensing (QS). Without the aforementioned process, gene expressions associated with virulence factors will not be produced. In this study, the sub-inhibitory concentrations (sub-MICs) of methanolic leaf extract and obtained fractions from Averrhoa bilimbi (kamias) were screened for ability to inhibit quorum sensing-controlled phenotypes of P. aeruginosa ATCC 27853.

Methodology: A. bilimbi crude extract was fractionated through liquid-liquid extraction, producing four (4) fractions: hexane fraction, dichloromethane (DCM) fraction, ethyl acetate (EtOAc) fraction, and water (H2O) fraction. Among the sub-MICs obtained from resazurin-based fluorimetric microtiter assay, only 50 μg/mL was utilized in evaluating the anti-QS properties of crude extract and fractions against P. aeruginosa ATCC 27853's virulence factors: swarming motility and production of pyocyanin.

Results: In the swarming motility assay, hexane fraction (9.39 mm ± 0.67) and DCM fraction (10.82 mm ± 0.95) displayed restriction in the treated P. aeruginosa ATCC 27853 swarms against the control (16.20 mm ± 2.55). In the anti-pyocyanin production assay, hexane fraction exhibited an inhibition of 42.66 % ± 12.94. TLC analysis and phytochemical screening revealed that hexane fraction contains steroids, terpenes, triterpenes, and glycolipids; and DCM fraction contains cardiac glycosides, triterpenoids, terpenes, triterpenes, steroids, alkaloids, and glycolipids.

Conclusion: Hexane and DCM fractions obtained from A. bilimbi significantly inhibited swarming of P.
aeruginosa ATCC 27853 while none of the extracts were able to significantly inhibit pyocyanin formation of P. aeruginosa ATCC 27853.