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Introduction
Communication among cells is a quintessential process synchronising assorted functions of higher organisms. Similar interaction also occurs amongst bacteria and is dependent on bacterial cell density. It is referred to as quorum sensing (QS). QS accounts for orchestrating bacterial functions and gene expression1 and is mediated by small diffusible molecules, autoinducers. The nature of these autoinducers is oligopeptides in gram-positive bacteria and N-Acyl Homoserine Lactones (AHLs) in gram- negative bacteria.2 Each bacterium produces autoinducers in small amounts. As the bacterial cell number increases so does the concentration of these autoinducers, thus reaching a threshold value. Subsequently, autoinducers bind to receptors on bacterial cell and trigger expression of certain genes while repressing other genes.3 This behaviour helps in biofilm formation, horizontal gene transfer, protease and exoenzyme antibiotic synthesis.
Proteus mirabilis and Serratia marcescens are gram-negative opportunistic pathogens causing nosocomial infections. P. mirabilis is primarily found associated with urinary tract infections, characterised by swarm migration.4 P. mirabilis forms biofilm in the host organism besides synthesising urease, hemolysin and other virulence factors.5 S. marcescens frequently appears as nosocomial pathogen causing infections of wound, respiratory tract and urinary tract. This bacterium produces virulence factors like protease and prodigiosin and forms biofilm. Besides, this bacterium exhibits swimming and swarming motility.6 Secretion of virulence factors and biofilm formation, under the control of QS facilitates bacteria to successfully establish infection in the host. Present technique of dealing with bacterial infection involves use of antibiotics that are lethal to bacteria, generating selective pressure that results in emergence of drug resistant strains.7 Thus, impeding QS would be a favourable method of dealing with bacterial infections caused by multi-drug resistant (MDR) bacteria without causing selective pressure on them.
Fatty acids (saturated and unsaturated) and their derivatives have been reported to possess antimicrobial properties; specifically fatty acids containing two double bonds, like linoleic acid, is more potent bacteriostatic compound.8 Moreover, conjugated linoleic acid has also been described to inhibit bacterial growth through lipid peroxidation in the membranes.9 Recent studies made on the effect of conjugated linoleic acid on colon, has indicated its ability to offset the development of inflammatory lesions.10 Linoleic acid and fatty acids like oleic acid, palmitic acid and stearic acid are...