Bacterial Metabolic State More Accurately Predicts Antibiotic Lethality Than Growth Rate

Abstract

Growth rate and metabolic state have been separately shown to affect antibiotic efficacy1–3. However, the two are interrelated since bacterial growth inherently imposes a metabolic burden4; thus, determining individual contributions from each is challenging5,6. Indeed, faster growth is often correlated with increased antibiotic efficacy7,8; however, the concurrent role of metabolism on that relationship has not been well characterized. As a result, a clear understanding of the interdependence between growth and metabolism, and their implication for antibiotic efficacy, remains lacking9. In this study, we measured growth and metabolism in parallel across a broad range of coupled and uncoupled conditions to determine their relative contribution to antibiotic lethality. We show that when growth and metabolism are uncoupled, antibiotic lethality uniformly depends on the bacterial metabolic state at the time of treatment, rather than growth rate. We further reveal a critical metabolic threshold below which antibiotic killing is negligible. These findings were general for a wide range of conditions, including nine representative bactericidal drugs, and diverse Gram-positive and -negative species (Escherichia coli, Acinetobacter baumanii, and Staphylococcus aureus). This work provides a cohesive metabolic-dependent basis for antibiotic-mediated cell death, with implications for current treatment strategies and future drug development.