New screening method assesses the impact of low-dose drug mixtures in the environment

Researchers are increasingly concerned about the impact on microorganisms and wildlife from the long-term exposure to low-dose mixtures of antibiotics, lipid regulators, psychiatric drugs, and other medicines that end up in aquatic environments. A new study suggests that existing approaches to studying these environmental risks—which typically measure the risk of individual chemicals separately and then add them together—may not provide a realistic assessment of the harm being done, particularly for low-dose mixtures containing antibiotics. Seeking a better alternative, a team led by Francisca Fernández-Piñas of the Autonomous University of Madrid, Rafael Muñoz-Carpena of the University of Florida, and their collaborators has developed a combined computational and experimental high-throughput screening method that involves studying the effects of chemical mixtures on cyanobacteria, a group of microorganisms found abundantly in water systems (Sci. Adv. 2016, DOI: 10.1126/sciadv.1601272). The team created 180 mixtures of 16 pharmaceutical and personal care product chemicals at nanogram to microgram levels. The researchers modified the cyanobacteria so that they would be bioluminescent and then tracked the toxicity impact of the mixtures by measuring light intensity. For example, the bacteria produce fewer bioluminescent proteins, and thus emit less light, when they are struggling with the toxicity of specific drug mixtures.