Heterogeneity in the response to the metabolic environment drives fosfomycin heteroresistance.

Heteroresistance is a form of antibiotic resistance in which a phenotypically unstable subpopulation of resistant cells coexists with a majority susceptible population. Many mechanisms of heteroresistance are unclear and the impact of the extracellular environment on this phenomenon is unknown. Studying fosfomycin heteroresistance in Enterobacter cloacae complex, we observed that glucose availability greatly increased the frequency of the resistant subpopulation. Glucose downregulated the glycerol and fosfomycin importer GlpT via catabolite repression. Heteroresistance was generated by heterogeneity in single-cell expression of GlpT, in addition to expression of fosA, which acted as a resistance enhancer. Due to the impact of environmental glucose on glpT expression, we observed that the resistant subpopulation was more frequent during infection in murine models of hyperglycemia/diabetes. Thus, we reveal a paradigm where heterogeneity in response to the environment tunes resistant subpopulation frequency, which suggests that the metabolic context of infection in specific disease states may be important to consider in treatment decisions.