Targeting KPC-Producing Klebsiella pneumoniae Biofilms: Genomic Profiles, Clinical Outcomes and Novel Combinations

New beta-lactam/beta-lactamase inhibitor combinations (BL/BLICs) are licensed for Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) infections. However, data regarding their efficacy against bacterial biofilms and the potential of synergistic combinations remain limited. This study evaluated their efficacy on planktonic and biofilm forms of KPC-Kp isolated from catheter-related bloodstream infections (CRBSIs), correlating findings with genomic and clinical data. Twelve KPC-3-harboring isolates (ST512, n = 7; ST307, n = 3; ST101, n = 2) were characterized via whole-genome sequencing. Ceftazidime/avibactam (CAZ/AVI), meropenem/vaborbactam (MEM/VAB), and imipenem/relebactam (IMI/REL) were tested alone or combined with fosfomycin (FOS), cefepime (FEP), meropenem (MEM), or imipenem (IMI) using checkerboard assays. All BL/BLICs alone showed significant, comparable efficacy against biofilm-producing strains. However, combination testing revealed heterogeneous synergistic profiles. CAZ/AVI combined with MEM, IMI, or FEP achieved 100% synergy in both planktonic and biofilm states. MEM/VAB-based combinations demonstrated consistent synergy (50–100%), whereas IMI/REL showed higher synergistic rates in biofilm than in planktonic forms. Conversely, FOS-based regimens were significantly less effective against biofilms. These findings provide a clinical rationale for selecting optimized dual regimens to eradicate biofilms, offering a critical therapeutic strategy to preserve vascular devices when catheter removal is unfeasible.