The role of quorum sensing in antimicrobial action

Quorum sensing is the coordinated behaviour of bacterial cells to act like a multicellular organism. Cell to cell signaling has impact on the control of culture biomass, biofilm formation, motility and the expression of the virulence genes. Bacterial persistence is the emergence of a neither dying nor actively dividing population of cells amoung dying cells in the presence of antimicrobials. These persisters are considered responsible for treatment failures in infectious diseases such as biofilm infections. In this study, the role of universal autoinducer, autoinducer-2 (AI-2) in persistence of Escherichia coli cells in the presence of ampicillin has been investigated. For this purpose, recombinant DNA techniques was used to construct luxS positive and negative isogenic mutants of E. coli K12 DH5?. Time kill assay was performed by using these mutants in the presence of ampicillin. After the addition of ampicillin to the media, the decrease in live cell mass was similar in luxS positive and negative bacterial cultures until the end of 120 minutes. Beyond this time point, a sharp decrease in surviving luxS negative bacteria. As a result, AI-2, an important mediator of quorum sensing, is suggested to play an important role in bacterial persistence in the presence of antimicrobial agents.