Combination of Ceftazidime-Avibactam and Aztreonam Effectively Treated Post-Cardiac Surgery Pneumonia Caused by Hypervirulent KPC- and NDM-Producing Klebsiella pneumoniae: A Case Report

Qimei Wei,1,* Rong Cong,1,* Chang Shen,2 Chen Chen,1 Zheng Cao,1 Chanjun Ren,3 Tingting Liu2 1Department of Clinical Laboratory, Wuhan Asia Heart Hospital, Wuhan, 430022, People’s Republic of China; 2Department of Cardiac Critical Care Medicine, Wuhan Asia Heart Hospital, Wuhan, 430022, People’s Republic of China; 3Department of Laboratory Medicine, Wuhan Kingmed Center for Clinical Laboratory, Wuhan, 430022, People’s Republic of China*These authors contributed equally to this workCorrespondence: Tingting Liu, Department of Cardiac Critical Care Medicine, Wuhan Asia Heart Hospital, No. 753 Jinghan Avenue, Jianghan District, Wuhan, 430022, People’s Republic of China, Tel +86 18627794672, Email [email protected]: Hypervirulent carbapenem‑resistant Klebsiella pneumoniae (hv-CRKP) co‑producing Klebsiella pneumoniae carbapenemase‑2 (KPC‑2) and New Delhi metallo‑β‑lactamase‑1 (NDM‑1) represents a serious clinical threat due to limited treatment options and high mortality. This study aimed to describe the clinical course, microbiological characteristics, and therapeutic outcome of a severe postoperative pneumonia caused by such a strain, and to evaluate the effectiveness of combination antimicrobial therapy.Case Presentation: A 59‑year‑old woman developed severe pneumonia and acute respiratory distress syndrome following cardiac surgery. Bronchoalveolar lavage fluid culture yielded carbapenem‑resistant K. pneumoniae. Antimicrobial susceptibility testing showed resistance to meropenem (minimum inhibitory concentration [MIC] ≥ 16 μg/mL), ceftazidime‑avibactam (CZA) (MIC ≥ 16/4 μg/mL), and aztreonam (ATM) (MIC ≥ 64 μg/mL). Molecular analysis identified blaKPC and blaNDM carbapenemase genes and hypervirulence‑associated genes including rmpA and iucA. In vitro synergy testing demonstrated a marked reduction in MIC (≤ 1 μg/mL) when CZA was combined with ATM. Based on these findings, combination therapy was initiated, resulting in rapid clinical improvement, a decline in procalcitonin levels from 4.83 ng/mL to 0.5 ng/mL, radiographic resolution of pulmonary infiltrates, and sustained microbiological clearance.Conclusion: This case demonstrates that CZA combined with ATM may be an effective therapeutic option for severe infections caused by hypervirulent KPC‑2‑ and NDM‑1‑producing K. pneumoniae. Early molecular identification and synergy‑guided antimicrobial therapy are essential for optimizing outcomes in critically ill patients.Keywords: Carbapenem-resistant Klebsiella pneumoniae, hypervirulent Klebsiella pneumoniae, KPC, NDM, ceftazidime-avibactam, aztreonam