Abstract
The in vitro activity of ceftolozane in combination with tazobactam (fixed concentration of 4 μg/ml) was evaluated against 2,435 Pseudomonas aeruginosa clinical isolates obtained from across Canada using Clinical and Laboratory Standards Institute broth microdilution methods. The MIC50 and MIC90 values for ceftolozane-tazobactam were 0.5 μg/ml and 1 μg/ml, respectively (a 32-fold-lower MIC90 than that for ceftazidime). Eighty-nine percent (141/158) of multidrug-resistant isolates were inhibited by ≤8 μg/ml of ceftolozane-tazobactam.