In vivo efficacy of ceftolozane against Pseudomonas aeruginosa in a rabbit experimental model of pneumonia: comparison with ceftazidime, piperacillin/tazobactam and imipenem.

The aim of this study was to compare ceftolozane with ceftazidime, piperacillin/tazobactam (TZP) and imipenem in an experimental rabbit model of Pseudomonas aeruginosa pneumonia. Efficacy was assessed following 2 days of treatment by total colony counts in different tissues (lung, spleen and blood culture). Mean ± standard deviation pulmonary bacterial loads were 4.9 ± 0.3, 3.6 ± 0.3, 4.8 ± 0.2, 5.5 ± 0.8 and 3.9 ± 0.3 log₁₀CFU/g of lung for ceftolozane (1g), ceftolozane (2g), ceftazidime, TZP and imipenem, respectively, compared with 6.3 ± 0.9 log₁₀CFU/g of lung for control animals. The higher ceftolozane dose [2g three times daily (t.i.d.)] showed significantly better efficacy than the lower dose (1g t.i.d.). In conclusion, in this rabbit model of P. aeruginosa pneumonia, ceftolozane had an efficacy equivalent to that of comparator agents at a dose of 1g t.i.d. and had better efficacy at a higher dose (2g t.i.d.).