Quorum sensing inhibitors: how strong is the evidence?

• Quorum sensing inhibitors are promising novel biocontrol agents.
• Most inhibitors are identified using biosensors, a procedure that is prone to bias.
• Adequate control experiments are needed to exclude false positives.
• Toxicity to biosensors should be carefully assessed as well.

Because of its promising effect as an alternative to antibiotics, quorum sensing disruption is an intensively studied field, and there are many studies that describe the quorum sensing inhibitory activity of natural and synthetic compounds. In this opinion article, we present an overview of recent literature with respect to quorum sensing inhibitors. Most of this research is based on experiments with quorum sensing signal molecule reporter strains. However, these experiments are prone to bias due to other effects compounds may have on reporter strains. We argue that researchers should perform adequate control experiments and should carefully assess toxicity of the compounds in the bacterial species they are working with in order to confirm that what they observe really is quorum sensing inhibition.