Successful use of outpatient parenteral antimicrobial therapy (OPAT) aztreonam-avibactam in a pediatric case of an infectious pseudoarthrosis caused by NDM-producing Klebsiella pneumoniae and Pseudomonas aeruginosa.

Osteoarticular infections caused by multidrug-resistant Gram-negative organisms represent a major therapeutic challenge, particularly in pediatric patients with complex traumatic injuries. We report a case of infectious pseudoarthrosis of the distal tibia caused by New Delhi metallo-β-lactamase (NDM)-producing Klebsiella pneumoniae and Pseudomonas aeruginosa in a 9-year-old girl with war-related trauma. Following surgical management and microbiological diagnosis, antimicrobial therapy with aztreonam-avibactam (ATM-AVI) was initiated as off-label treatment due to limited therapeutic alternatives. The regimen was administered initially during hospitalization and subsequently through outpatient parenteral antimicrobial therapy (OPAT) using elastomeric infusion devices. During treatment, a transient elevation of liver enzymes prompted temporary interruption of therapy, after which treatment was safely resumed once values normalized. The patient completed six weeks of therapy with good clinical tolerance and no evidence of recurrent infection at follow-up. This case illustrates the potential role of ATM-AVI as a therapeutic option for pediatric osteoarticular infections caused by MBL-producing organisms and highlights the feasibility of OPAT administration in this setting.