Subinhibitory concentrations of the penicillin antibiotics induce quorum-dependent violacein synthesis in <Emphasis Type="Italic">Chromobacterium violaceum</Emphasis>

The goal of the work was to analyze the ability of natural and semisynthetic penicillins to regulate the quorum sensing system in bacteria. The test strain was C. violaceum NCTC 13274 (CV 026) bearing mini-Tn5 insertion in the cviI gene that led to irreversible loss of N-acyl-L-homoserine lactone (AHL) biosynthesis and reversible suppression of violacein biosynthesis. Within the temperature range suboptimal for C. violaceum growth (17–22°C), subinhibitory concentrations of piperacillin, azlocillin, ticarcillin, carbenicillin, and oxacillin showed a quorum-dependent induction of violacein production, probably acting as AHL-mimetics. Cleavage of these antibiotics with beta-lactamase I and II led to the loss of both antibacterial and quorum-inducing activities. Inhibition of C. violaceum beta-lactamase by sulbactam resulted in manifestation of combined antibacterial and quorum-inducing activity of ampicillin and amoxicillin. These results improve our understanding of the role of beta-lactams and beta-lactamases in the processes of interspecific antagonism and in microbial intercellular communication.     

Quorum Sensing Inhibition in Chromobacterium violaceum by Amikacin Combination with Activated Charcoal or Small Plant-Derived Molecules (Pyrogallol and Coumarin)

Microbiology - The study was aimed at effective inhibition of quorum sensing (QS) in the model bacterium Chromobacterium violaceum ATCC 31532 by combinations of compounds with different anti-QS...     

Inhibitory effect of aminoglycosides and tetracyclines on quorum sensing in <Emphasis Type="Italic">Chromobacterium violaceum</Emphasis>

Effect of aminoglycosides (kanamycin, gentamycin, and amikacin) and tetracyclines (tetracycline and doxycycline) on the CviI/CviR two-component quorum sensing mediated with C₆-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 C₆-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 C₆-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 C₆-AHL production within a broad concentration range; and therefore quorum sensing in C. violaceum ATCC 31532 did not function because of C₆-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.     

Quorum Sensing in Chromobacterium subtsugae (Formerly,C. violaceum) Is Inhibited by Gamma-Lactones,the Minor Components of Eucalyptus Leaf Extract

Microbiology - The goal of the study was to investigate the mechanism of quorum sensing (QS) inhibition in the model bacterium Chromobacterium subtsugae 026 (formerly, C. violaceum 026) by...