Efficacies of ceftazidime–avibactam (4:1 w/w) and ceftazidime were tested against ceftazidime-susceptible (blaKPC-2-negative), and meropenem- and ceftazidime-resistant (blaKPC-2-positive), Klebsiella pneumoniaein a 52-h, multiple dose, abdominal abscess model in the rat. Efficacies corresponded to minimum inhibitory concentrations (MICs) measured in vitroand were consistent with drug exposures modelled from pharmacokinetics in infected animals. The ceftazidime, ceftazidime–avibactam and meropenem control treatments were effective in the rat abscess model against the susceptible strain, whereas only ceftazidime–avibactam was effective against K. pneumoniaeharbouring blaKPC-2.