Inhibitory Effect of Aminoglycosides and Tetracyclines on Quorum Sensing in Chromobacterium violaceum

Effect of aminoglycosides (kanamycin, gentamycin, and amikacin) and tetracyclines (tetracycline and doxycycline) on the CviI/CviR two-component quorum sensing mediated with C-6-AHL autoinducer in Chromobacterium violaceum ATCC 31532 was studied. All antibiotics showed growth-inhibitory activity against the test strain and violated its density-dependent communication system in sub-inhibitory concentrations, which could be seen as suppression of C-6-AHL-dependent violacein biosynthesis. The tested antibiotics exhibited an alternative balance of these activities: a direct antibacterial effect prevailed in tetracyclines, while aminoglycosides inhibited quorum sensing system of C. violaceum ATCC 31532 within a broad concentration range. Sensor strains capable of quantitative detection of C-6-AHL and bearing the genes of resistance to aminoglycosides (C. violaceum 026) or tetracyclines (Escherichia coli pAL103) were used to analyze the effect of antibiotics on autoinducer accumulation in the cultivation medium. Aminoglycosides were found to suppress C-6-AHL production within a broad concentration range; and therefore quorum sensing in C. violaceum ATCC 31532 did not function because of C-6-AHL limitation. The obtained results were analyzed in relation to their biological role in natural microbiocenoses, as well as in relation to antibiotic treatment of bacterial infections caused by organisms using quorum sensing for induction of their pathogenic potential.