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 log10 CFU/g of lung for ceftolozane (1 g), ceftolozane (2 g), ceftazidime, TZP and imipenem, respectively, compared with 6.3 ± 0.9 log10 CFU/g of lung for control animals. The higher ceftolozane dose [2 g three times daily (t.i.d.)] showed significantly better efficacy than the lower dose (1 g 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 1 g t.i.d. and had better efficacy at a higher dose (2 g t.i.d.).