[Bacterial communication: quorum-sensing]

The interaction between the host and a pathogenic bacterium is mainly controlled by the bacterial population size. An individual bacterial cell is able to sense other members of the same species and in response, differentially expresses specific genes. Such cell to cell communication is called quorum sensing (QS) and involves the direct or indirect activation of a response regulator by a signal molecule. The major QS signal molecules are N-acyl homoserine lactones in Gram negative bacteria and post-translationally modified peptides in Gram positive bacteria. QS system is used by a wide variety of bacteria including human pathogens. QS genes are important for the pathogenic potential of Pseudomonas aeruginosa and Staphylococcus aureus, as well as other invasive bacteria. Thus QS interfering molecules promise new therapeutic strategies or prophylactic measures in infectious diseases. In this review article, the role of QS system on bacterial virulence, its effects on the host immune response and QS inhibitors for prophylaxis and therapy are discussed.