Successful treatment of NDM-type carbapenemase-producing CRKP bacteremia and intra-abdominal infection in severe acute pancreatitis with aztreonam-avibactam: a case report

Background Carbapenem-resistant Klebsiella pneumoniae (CRKP), particularly NDM-type carbapenemase-producing isolates, remains a major therapeutic challenge in critically ill patients. Severe acute pancreatitis (SAP) may be complicated by intra-abdominal infection (IAI) and bloodstream infection (BSI), requiring timely antimicrobial susceptibility assessment to guide therapy. Case Presentation A 40-year-old male with SAP was admitted on hospital day 1 (D1) with respiratory and circulatory failure and multiple organ dysfunction. After initial stabilization, he developed recurrent fever with rising inflammatory markers. Blood and peripancreatic drainage fluid specimens obtained on D22 subsequently yielded CRKP with concordant susceptibility profiles. Phenotypic testing was suggestive of metallo-β-lactamase production and demonstrated marked in vitro activity of aztreonam-avibactam (ATM-AVI) (inhibition zone 32 mm; MIC <0.064 mg/L), whereas ceftazidime-avibactam (CZA) was inactive (MIC >16 mg/L). Based on these phenotypic susceptibility results, targeted ATM-AVI therapy (2 g plus 0.5 g IV every 6 h) was initiated on D27. Subsequent whole-genome sequencing identified a blaNDM-like carbapenemase gene with 99.3% sequence identity to blaNDM-1 , providing mechanistic characterization of the resistance phenotype. Blood cultures on D34 and D39 were negative. Fever resolved, inflammatory markers decreased, and clinical improvement was observed without radiological progression. Therapeutic drug monitoring (TDM) confirmed adequate plasma exposure, and no clinically significant hepatic, renal, or hematologic abnormalities were observed. Conclusion The favorable clinical and microbiological outcome occurred in the context of combined source control and phenotypic susceptibility-guided ATM-AVI therapy, with subsequent WGS providing mechanistic characterization of the resistance phenotype.