Disruption of bacterial quorum sensing: an unexplored strategy to fight infections in aquaculture

Disease outbreaks-some of them caused by pathogenic bacteria-are considered to be one of the largest constraints to development of the aquaculture sector. So far, antibiotics and disinfectants have only had limited success in the prevention or cure of aquatic disease. Moreover, the frequent use of biocides, especially in subtherapeutic doses, is leading to the rapid development of resistance. Therefore, there is an urgent need to develop alternative ways to control infections caused by bacterial pathogens in aquaculture. Many of these pathogens are found to control virulence factor expression by a cell-to-cell communication system. Hence, disruption of bacterial quorum sensing has been proposed as a new anti-infective strategy and several techniques that could be used to disrupt quorum sensing have been investigated. These techniques comprise (1) the inhibition of signal molecule biosynthesis, (2) the application of quorum sensing antagonists (including natural occurring as well as synthetic halogenated furanones, antagonistic quorum sensing molecules and undefined exudates of higher plants and algae), (3) the chemical inactivation of quorum sensing signals by oxidised halogen antimicrobials, (4) signal molecule biodegradation by bacterial lactonases and by bacterial and eukaryotic acylases and (5) the application of quorum sensing agonists. The few reports that deal with disruption of quorum sensing of aquatic pathogens, together with the results obtained with human and plant pathogens, indicate that this new approach has potential in fighting infections in aquaculture. However, before this new strategy can be applied in aquaculture, the impact of quorum sensing disruption on the virulence of aquatic pathogens and the impact of the proposed quorum sensing disrupting techniques on the aquaculture system of interest should be studied in more depth. (C) 2004 Elsevier B.V All rights reserved.