Qq vibrio

The ISME Journal (2008) 2, 19–26 & 2008 International Society for Microbial Ecology All rights reserved 1751-7362/08 $30.00
www.nature.com/ismej

MINI-REVIEW

Quorum sensing and quorum quenching in Vibrio harveyi: lessons learned from in vivo work
Tom Defoirdt1,2, Nico Boon1, Patrick Sorgeloos2, Willy Verstraete1 and Peter Bossier2
1 2

Laboratory of Microbial Ecology and Technology(LabMET), Ghent University, Ghent, Belgium and Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Ghent, Belgium

Luminescent vibrios, bacteria belonging to the species Vibrio harveyi and closely related species, are important pathogens in aquaculture that can affect almost all types of cultured animals. Due to large-scale use of antibiotics, many luminescent vibrios haveacquired (multiple) resistance, which render antibiotic treatments ineffective. One of the alternative strategies that has recently been developed to control infections caused by antibiotic-resistant bacteria is the disruption of quorum sensing, bacterial cell-to-cell communication. The quorum sensing system of V. harveyi has been studied quite intensively in vitro. Recent studies have been directedtowards understanding the impact of quorum sensing and quorum sensing disruption on the virulence of luminescent vibrios towards different host organisms in vivo. This mini-review aims at discussing the current knowledge of quorum sensing in luminescent vibrios in vivo. Subsequently, quorum quenching by halogenated furanones is discussed and finally, some directions for further research arepresented. The ISME Journal (2008) 2, 19–26; doi:10.1038/ismej.2007.92; published online 25 October 2007 Subject Category: microbe–microbe and microbe–host interactions Keywords: quorum sensing; quorum quenching; luminescent vibriosis; aquaculture

Introduction
Vibrio harveyi and closely related species such as Vibrio campbellii and Vibrio parahaemolyticus are amongst the most important bacterialpathogens in the intensive rearing of molluscs, finfish and especially shrimp (Austin and Zhang, 2006). Vibrios are opportunists that only cause disease when the host organisms are immune-suppressed or otherwise physiologically stressed, with the frequency of infection often being attributable to adverse culture conditions (Alderman and Hastings, 1998). In our laboratories, adverse culture conditionsare simulated in laboratory challenge tests by feeding the animals with a suboptimal diet (Defoirdt et al., 2005; Marques et al., 2005; Tinh et al., 2007b). In order to overcome the negative consequences of adverse culture conditions, farmers traditionally rely on the use of antibiotics (Subasinghe et al., 2001). Due to the indiscriminate misuse of antibiotics in aquaculture (Cabello, 2006),vibrios are now resistant to several antibiotics and consequently, antibiotics are no longer effective in treating
Correspondence: T Defoirdt, Laboratory of Microbial Ecology and Technology, Ghent University, Coupure Links 653, Ghent B-9000, Belgium. E-mail: Tom.Defoirdt@UGent.be

luminescent vibriosis. Karunasagar et al. (1994), for instance, reported mass mortality in tiger shrimp (Penaeusmonodon) larvae caused by V. harveyi strains with multiple antibiotic resistance that was linked to the use of antibiotics in hatcheries. Hence, the quest for alternative methods to control infections caused by antibiotic-resistant bacteria is an important challenge for the sustainable development of aquaculture.

Quorum sensing—bacterial cell-to-cell communication
One of the new strategies that hasbeen proposed to control infections in aquaculture is disruption of quorum sensing, bacterial cell-to-cell communication by means of small signal molecules (Defoirdt et al., 2004). Quorum sensing is a mechanism of gene regulation in which bacteria coordinate the expression of certain genes in response to the presence or absence of small signal molecules. This mechanism was first discovered in the...