 This study examined how antibiotic interactions affect the development of antibiotic resistance in E. coli populations growing in wastewater. The researchers found that antibiotic interactions can either increase or decrease the rate at which bacteria develop resistance. Synergistic interactions between two antibiotics resulted in lower levels of resistance compared to when the same antibiotics were administered individually. Antagonistic interactions also decreased resistance, but to a lesser extent. Additionally, the researchers observed that the rate of resistance development was dependent upon the ratio of antibiotics present in the environment. This suggests that the relative concentration of antibiotics is important in determining whether they will promote or inhibit the development of resistance. This article was authored by Endorica Sutradha, Kali Ching, Daash Desai, and others.