Aztreonam/avibactam during continuous venovenous haemodiafiltration in a critically ill patient with NDM-producing Klebsiella pneumoniae: a case report and review of the literature

Purpose: Aztreonam/avibactam represents a valuable therapeutic option for infections caused by metallo-β-lactamase-producing Enterobacterales, but data on its use during continuous renal replacement therapy (CRRT) are scarce and largely limited to a single pharmacokinetic report. Here, we describe the clinical course of a 76-year-old woman with end-stage renal disease who received aztreonam/avibactam while undergoing continuous venovenous haemodiafiltration (CVVHDF) during a critical illness secondary to a presumed invasive infection by NDM-producing Klebsiella pneumoniae. Methods: Ceftazidime/avibactam plus aztreonam was started empirically for fever, pyuria and a urinary NDM-producing K. pneumoniae isolate, then switched to co-formulated aztreonam/avibactam after surgery and ICU transfer (intermittent-haemodialysis phase: loading 1 g/0.333 g, then 0.675/0.225 g every 12 h as a 3-h infusion). When CVVHDF was started for worsening sepsis, the regimen was changed to a 2 g/0.667 g loading dose followed by 1 g/0.333 g every 8 h given as an uninterrupted continuous infusion, replicating the only previously reported CVVHDF regimen. Results: The course was confounded by vancomycin-resistant Enterococcus faecium bacteraemia, bowel ischaemia with perforation, stercoral peritonitis and polymicrobial intra-abdominal infection. No microbiologically documented recurrence of the NDM-producing organism occurred after treatment, although rectal colonization persisted. Conclusions: The case demonstrates the practical feasibility of continuous-infusion aztreonam/avibactam during CVVHDF. Efficacy and PK/PD target attainment cannot be confirmed, as susceptibility testing for the index strain and therapeutic drug monitoring were unavailable.