Aspirin versus cyclooxygenase-2 inhibitors as quorum sensing inhibitors of Pseudomonas aeruginosa

Background: Quorum sensing (QS) systems, which are intra and inter species, signaling systems regulate expression of several genes, many of these coding for virulence factors.Quorum sensing inhibitors (QSIs) are chemicals that interfere with QS-controlled gene regulation.Pseudomonas aeruginosa has the most accurately studied bacterial QS behavior.Objectives: Our work aimed to compare in vitro effects of Aspirin versus Cyclooxygenase-2 (COX-2) inhibitor (Etodolac) on QS-controlled virulence factors of Pseudomonas aeruginosa.Methodology: Our study was conducted on thirty Pseudomonas aeruginosa isolates which were identified by standard bacteriological techniques.We tested the effects of Aspirin versus Etodolac on the production of QS-controlled virulence factors: biofilm formation: using microtiter plate crystal violet assay, Pyocyanin production by chloroform extraction and elastase production by Elastin Congo Red assay.Results: Twenty five percent of the isolates had inhibited biofilm formation ability and elastase enzyme activity with each of the two drugs.Pyocyanin production was more sensitive to the QSIs, with as much as 73.3% of isolates being inhibited by Aspirin and 40% of them were inhibited with Etodolac.Etodolac showed stronger inhibition activity of 49.8% for pyocyanin pigment production versus Aspirin which had only 28.1%.Aspirin more strongly inhibited biofilm formation by 32.6% in contrast to 20.4% by Etodolac.Both Aspirin and Etodolac exhibited comparable inhibition of 51.6% and 56% for elastase enzyme production respectively.Conclusions: COX-2 inhibitors were shown to have effective QSI effects.Both Aspirin and Etodolac had comparable inhibitory strengths.