Time–kill curves with polymyxin B (PMB) and meropenem (MEM) alone and in
combination against an initial inoculum of ca. 106 CFU/mL of
PMB-susceptible clinical isolates BRKP21, BRKP61 and BRKP76 and PMB-resistant
isolates BRKP67 and BRKP28 over 24 h: PMB (0.5, 2, 4, 16 and 256 mg/L) and MEM
(40, 60 and 120 mg/L) as monotherapy (A1–E1, monotherapy); PMB (0.5 mg/L
and 2 mg/L) in combination with meropenem (20, 40, 60 and 120 mg/L)
(A2–E2, combination); and PMB (4 mg/L and 16 mg/L) in combination with
meropenem (20, 40, 60 and 120 mg/L) (A3–E3, combination). Black dashed
line represents the limit of quantification for CFU/mL bacterial count.