Bacterial strains, growth media, and culturing conditions

We characterized bacterial isolates from a library assembled by the Duke Hospital’s Division of Infectious Diseases. This library consists of approximately 80 isolates that have been identified as ESBL producers. Unless otherwise noted, Klebsiella pneumoniae isolate DICON 005 was used. As a sensitive bacteria control, Escherichia coli MC4100 cells were used. Unless otherwise indicated, experiments were conducted in M9 medium [1× M9 salts (48 mM Na₂HPO₄, 22 mM KH₂PO₄, 862 mM NaCl, and 19 mM NH₄Cl), 0.4% glucose, 0.2% casamino acids (Teknova), 0.5% thiamine (Sigma), 2 mM MgSO₄, and 0.1 mM CaCl₂]. For overnight cultures, we inoculated single colonies from an agar plate into 2 ml of M9 and incubated them for 12 hours at 30°C.