Fig. 3

Relebactam enhances the activity of imipenem among chromosomal AmpC–nonproducing Enterobacterales isolates. A all (N = 78,766). B imipenem-NS (N = 5859). C imipenem-S (N = 72,907). Percentage represents n/N × 100%, where n was the number of isolates meeting the MIC threshold and N was the total number of isolates based on the CLSI 2021 clinical breakpoints for imipenem and imipenem/relebactam (both MIC ≤ 1 μg/mL for susceptibility) and subsequently categorized as either S (MIC ≤ 1 μg/mL) or NS (MIC > 1 μg/mL) [18]. The dashed line indicates the CLSI 2021 imipenem and imipenem/relebactam susceptibility breakpoints. The arrows indicate mode MIC values. Enterobacterales chromosomal AmpC–nonproducing species included Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca, and Citrobacter koseri. AmpC, Ambler class C β-lactamase; CLSI, Clinical and Laboratory Standards Institute; MIC, minimum inhibitory concentration; NS, nonsusceptible; S, susceptible